MCAT Biology Review

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  1. Eukaryotic cells include: animal cells, and what other cells...
    plant cells and fungal cells
  2. What is the difference between eukaryotic cells and prokaryotic cells?
    Eukaryotic cells have a well-defined nucleus bound by a nuclear membrane with a variety of organelles located outside the nuclear membrane. Prokaryotic cells are those that lack a well-defined membrane-bound nuclei and a full complement of the organelles. (Prokaryotes include bacteria.
  3. What is the cell wall largely composed of?
  4. What is the cell membrane primarily composed of?
    Protein and phospholipid
  5. The phospholipid bilayer features:
    A. lipid-soluble components.
    B. both lipid-soluble and water-soluble components.
    C. neither lipid-soluble nor water-soluble components.
    D. water-soluble components.
    B. The cell membrane is composed primarily of protein and phospholipid. The phospholipid molecules have both lipid-soluble components and water-soluble components.
    (this multiple choice question has been scrambled)
  6. The hydrophobic moieties of the cell membrane's phospholipid molecules are oriented:
    A. toward the inner portion of the membrane.
    B. toward the external environment surrounding the membrane.
    C. both toward the inner portion of the membrane and the external environment .
    D. neither toward the inner portion of the membrane nor the external environment.
    A. The cell's internal and external environments are water rich and therefore tend to repel the hydrophobic moieties.
    (this multiple choice question has been scrambled)
  7. A typical animal cell contains all of the following except:
    A. a discrete nucleus.
    B. microtubules.
    C. a cell wall.
    D. a mitochondrion.
    C. The outmost layer of an animal cell is the cell membrane, which is composed of protein and phospholipid.
    (this multiple choice question has been scrambled)
  8. The cell membrane has what type of permeability?
    It is semipermeable and due to its permeability allowing a given substance passage in a select set of circumstances and denying the same substance passage in other circumstances, it is selectively permeable.
  9. What is simple diffusion?
    A process that occurs in a system of fluid where solute and solvent particles tend to disperse themselves so that the solute concentration is uniform throughout the system.
  10. What is osmosis?
    When a system employs a membrane that allows water to diffuse but not a given solute, the water will tend to move via simple diffusion in an effort to equalize the concentration of the solute.
  11. What is the definition of hypertonic (or hyperosmotic)?
    Hypertonic refers to a greater concentration. In biology, a hypertonic solution is one with a higher concentration of solutes on the outside of the cell. When a cell is immersed into a hypertonic solution, the tendency is for water to flow out of the cell in order to balance the concentration of the solutes.
  12. Which of the following is NOT true of cell membranes?
    A. They regulate the cell's internal environment.
    B. They can alter their permeability to certain substances.
    C. They are universally permeable.
    D. They can mediate diffusion.
    C. The cell membrane helps the cell maintain homeostasis by regulating the movement of substances into and out of the cell.
    (this multiple choice question has been scrambled)
  13. Simple diffusion occurs because:
    A. cell membranes are permeable only to certain substances.
    B. within a given solution, solute and solvent molecules tend to distribute themselves in uniform concentration.
    C. cells expend energy to make it occur.
    D. the cell membrane regulates the cell's internal environment.
    B. Simple diffusion does not require the expenditure of energy by the cell.
    (this multiple choice question has been scrambled)
  14. Given the following list, assume that the axonal cell membrane is permeable only to potassium (K+), sodium (Na+), and calcium (Ca++), and that no cellular energy is available for transport, which of the following ion movements presented is most consistent with the data set forth in the table?
    Ion    ||  Cytoplasm       ||Blood    
    K+     ||  397(mmol/L)   || 20(mmol/L) 
    Na+   ||  50(mmol/L)     || 437(mmol/L)
    Cl-     ||  40(mmol/L)     || 556(mmol/L)
    Ca++  ||  0.4(mmol/L)    || 10(mmol/L)

    A. Sodium does not flow in either direction across the axonal cell membrane.
    B. Calcium flows from the blood into the axonal cytoplasm.

    C. Potassium flows out of the blood into the axonal cytoplasm.
    D. Chloride flows from the blood into the axonal cytoplasm.
    B. is correct.
    (this multiple choice question has been scrambled)
  15. If two solutions, X and Y, are separated by a membrane, and X has a higher solute concentration than does Y, it may be concluded that:
    A. solvent will move from X to Y.
    B. X is hypotonic to Y.
    C. Y is hypotonic to X.
    D. solute will move from Y to X.
    C. The question depends upon the meaning of the term hypotonic, which describes a solution with a solute concentration less than that of some other solution. Since solution X has a higher solute concentration, Y is hypotonic to X.
    (this multiple choice question has been scrambled)
  16. Which of the following correctly characterizes osmotic pressure?
    A. It tends to move solvent from a hypertonic to a hypotonic region.
    B. It tends to move solvent from a hypotonic to a hypertonic region.
    C. It tends to move solute from the hypotonic to a hypertonic region.
    D. It tends to move solute from a hypertonic to a hypotonic region.
    B. is correct.
    (this multiple choice question has been scrambled)
  17. Which of the following describes a form of passive diffusion?
    A. Osmosis
    B. Semipermeability
    C. Hypotonicity
    D. Hypertonicity
    A. Osmosis refers, in essence, to the passive diffusion of solvent.
    (this multiple choice question has been scrambled)
  18. What is facilitated diffusion or facilitated transport?
    It is where the carrier helps a solute diffuse across a membrane it could not otherwise penetrate. A type of passive transport that refers to the movement down the concentration gradients of certain lipid insoluble substances, these having little ability to cross the lipid bilayer without mediation by a specialized device. Facilitated diffusion proceeds via ion channels or pores within the cells membrane's protein components.
  19. What is active transport?
    It is where energy (i.e. ATP) is used to transport solutes against their concentration gradients. It is a process by which substances cross the cell membrane against their concentration gradients (from areas of lower concentration to areas of higher concentration). It requires the expenditure of energy.
  20. The sodium-potassium pump, also called Na+ -K+ ATPase, is a means by which the cell maintains a relatively fixed internal concentration of sodium and potassium ions. The pump continuously forces sodium ions out of the cell and draws potassium ions inward. In a typical Na+ -K+ ATPase, the cell moves three sodium ions outward for every two potassium ions drawn inward. A transmembrane protein facilitates this "ion exchange." Based on your knowledge of equilibria, would you speculate that the sodium-potassium pump represents active transport? Assuming that the cell membrane is permeable to both sodium and potassium ions, predict the ion flow that would follow if the pump were to suddenly cease operation.
    In order to continuously expel sodium and take in potassium, the cell must expend energy, since the activity contravenes prevailing concentration gradients. The pump itself produces and maintains the concentration gradients against which it operates: one in which the sodium concentration is higher on the outside of the cell than on the inside and the other in which the potassium concentration is higher on the inside of the cell than on the outside. The process demands energy, which is supplied by ATP. The pump defies the natural tendency for the solute concentrations to equilibrate. If it were to cease operating, the natural tendencies would manifest. Sodium would flow passively down its concentration gradient and enter the cell. Potassium would flow passively down its concentration gradient and exit the cell.
  21. What is endocytosis?
    A process by which cells can ingest particles larger than an ion or molecule. In this process, a small region of the lipid bilayer located near the target particle, invaginates, surrounding the target. The invaginating portion of the lipid bilayer eventually pinches off to create a vesicle, which harbors the particle within the cell's interior. If a solid particle was ingested by the cell (i.e. a bacterium), it is called phagocytosis. If fluid was ingested, it is pinocytosis.
  22. Endocytosis of liquids or small particles is termed _____________, whereas endocytosis of larger particles, like bacteria or foreign matter, is termed ___________.
    Pinocytosis: Phagocytosis
  23. Receptor-mediated endocytosis involves what?
    The ingestion of specific particles after they bind to specific protein receptors on the membrane.
  24. Which of the following is a form of endocytosis?
    I. Pinocytosis
    II. Expulsion
    III. Phagocytosis

    A. I only
    B. III only
    C. II only
    D. I and III only
    D. Phagocytosis describes the endocytosis of large particles, whereas pinocytosis describes the endocytosis of liquids or smaller particles.
    (this multiple choice question has been scrambled)
  25. What is exocytosis?
    It is, essentially, the reverse process of endocytosis. Things exiting the cells. The cell directs an intracellular vesicle to fuse with the plasma membrane thus releasing its contents to the exterior (i.e. neurotransmitters, pancreatic enzymes, etc.)
  26. Which among the following does NOT play a role in the process of endocytosis?
    A. Invagination
    B. Pinching off of the membrane
    C. Vesicle formation
    D. Ion channel
    D. An ion channel is an entity associated with facilitated transport, not endocytosis. Endocytosis is largely mediated by proteins within the cell membrane.
    (this multiple choice question has been scrambled)
  27. What, in general, are the three types of cellular adhesions that join cells together?
    • tight junctions: They link together portions of adjacent cell membranes to form a barrier. At a tight junction, there is no intercellular space. For example, tight junctions maintain the structural integrity of the small intestine's inner surface. There, they form the barrier that prevents the intestinal contents from leaking out between the cells.
    • gap junctions: They link together the cytoplasms of adjacent cells, and small particles, such as ions, can flow through them freely. They consist of protein channels that form a bridge between the two cells. Gap junctions are important in heart muscle contraction; they allow the heart's electrical signals to be passed quickly from cell to cell.
    • desmosomes: A desmosome is a cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes. Desmosomes help to resist shearing forces and are found in simple and stratified squamous epithelium. The intercellular space is very wide (about 30 nm). Desmosomes are also found in muscle tissue where they bind muscle cells to one another. They are composed of plaquelike proteins embedded in the cell membrane to which the cytoskeleton is attached. Desmosomes are responsible for the structural integrity of most tissues in the human body.
  28. Where and what is the endoplasmic reticulum?
    It is found throughout the cell cytoplasm and it is an interconnected membrane system resembling flattened sacs. There are two kinds: dotted with ribosomes on its surface is called rough ER and without ribosomes is called smooth ER. Rough ER is important in protein synthesis whereas smooth ER is a factor in phospholipid and fatty acid synthesis and metabolism. Smooth ER is also important in the liver to help detoxify many chemicals..
  29. What encloses the cell nucleus?
    The nuclear membrane which consists of two lipid bilayers—the inner nuclear membrane, and the outer nuclear membrane.
  30. What is the rough endoplasmic reticulum (rough ER) in close association with, which function in what synthesis?
    In close association with ribosomes which function in protein synthesis. The rough ER constitutes a principal site of cellular protein synthesis and its ribosomes are intimately involved in that process.
  31. The smooth endoplasmic reticulum (smooth ER) is devoid of what? Smooth ER does not participate in protein synthesis but is involved in what?
    Devoid of ribosomes and is involved in lipid synthesis and drug detoxification. The smooth endoplasmic reticulum (abbreviated SER) has functions in several metabolic processes. It synthesizes lipids, phospholipids, and steroids. Cells which secrete these products, such as those in the testes, ovaries, and skin oil glands have a great deal of smooth endoplasmic reticulum. It also carries out the metabolism of carbohydrates, drug detoxification, attachment of receptors on cell membrane proteins, and steroid metabolism. In muscle cells, it regulates calcium ion concentration. It is connected to the nuclear envelope. Smooth endoplasmic reticulum is found in a variety of cell types (both animal and plant), and it serves different functions in each. The smooth endoplasmic reticulum also contains the enzyme glucose-6-phosphatase, which converts glucose-6-phosphate to glucose, a step in gluconeogenesis.
  32. An abundant amount of rER and Golgi is found in cells which produce and secrete protein. Give an example.
    B-cells of the immune system which secrete antibodies, acinar cells in the pancreas which secrete digestive enzymes into the intestines, and goblet cells of the intestine, which secrete mucous into the lumen.
  33. What is the Golgi apparatus?
    The Export Department: It is a specialized derivative of the endoplasmic reticulum, consisting of a series of flattened sacs rather than channels. It forms a stack of smooth membranous sacs or cisternae that function in protein modification like the addition of polysaccharides (i.e. glycosylation). It is also responsible for packaging and transporting proteins to the cell surface, where they are either expelled into the extracellular space or incorporated into the cell membrane. This transport is accomplished through vesicles, which pinch off from the Golgi and migrate to the cell surface. They then fuse with the cell membrane and release their contents through the process of exocytosis. The Golgi apparatus is also thought to modify some proteins before expelling them from the cell.
  34. Among the following, which site is most closely associated with protein synthesis in the eukaryotic cell?
    A. The rough endoplasmic reticulum
    B. The smooth endoplasmic reticulum
    C. The nuclear membrane
    D. The Golgi apparatus
    A. Protein synthesis occurs on ribosomes, which may exist associated with endoplasmic reticulum, thus forming rough endoplasmic reticulum. (They may also float freely in the cytoplasm.)
    (this multiple choice question has been scrambled)
  35. Which among the following is a true statement regarding the Golgi apparatus?
    A. It functions in secretion.
    B. It is a derivative of the nuclear membrane.
    C. It functions in protein synthesis.
    D. It carries ribosomes on its surface.
    A. The Golgi apparatus is a derivative of the endoplasmic reticulum. The Golgi apparatus forms vesicles that contain secretory proteins, which are then expelled from the cell via exocytosis.
    (this multiple choice question has been scrambled)
  36. Cellular organelles include the enzyme containing entities called what?
    Peroxisomes and lysosomes
  37. What do peroxisomes contain?
    They contain catalase, an enzyme relevant to the processing of hydrogen peroxide.
  38. What do lysosomes contain?
    They harbor hydrolytic enzymes that digest foreign particles and senescent (aged) organelles. They are sometimes termed "suicide sacs." In a diseased cell, lysosomes may release their powerful acid hydrolases to digest away the cell (autolysis). In normal cells, a primary (normal) lysosome can fuse with an endocytotic vesicle to form a secondary lysosome where the phagocytose particle (i.e. a bacterium) can be digested (heterolysis). There are numerous lysosomes in phagocytic cells in the immune system (i.e. macrophages, neutrophils). [In plant cells, lysosomes house certain toxins, including alkaloids (primary amines).]
  39. What are vacuoles?
    They constitute spaces or vacancies within the cytoplasm. Often they are fluid-filled. [In protozoans, they function to expel wastes or excess fluid.]
  40. What are mitochondria?
    The power house. They are double-membraned organelles whose inner membrane has shelf-like folds called cristae that mediate the synthesis of ATP (adenosine triphosphate), the molecule associated with energy storage, through aerobic respiration. The matrix, the fluid within the inner membrane, contains the enzymes for the Kreb's cycle and circular DNA (the only cellular DNA found outside of the nucleus). They are commonly termed the cell's "energy currency."
  41. The inner mitochondrial membrane is folded into convolutions called ________.
  42. The interior of the inner mitochondrial membrane is termed the ________.
  43. The Krebs cycle and oxidative phosphorylation occur where? These processes produce the bulk of the ___ generated in aerobic (oxygen-using) organisms.
    • Within the mitochondria.
    • ATP
  44. Glycoproteins can stabilize the protein, facilitate its correct folding, be part of a lipid anchor for attaching the protein to a membrane, or provide the protein with surface characteristics that facilitate its recognition. In which of the following cellular components would the greatest proportion of glycoproteins be expected? 
    A. Phospholipid bilayer
    B. Mitochondria
    C. Lysosomes
    D. Microfilaments
    A. is correct. The question asks which of the cellular components has characteristics that would suit the special functions of a glycoprotein. A phospholipid bilayer is a membrane, and one of the functions of the oligosaccharide attached to a protein is to anchor the protein to a membrane.
    (this multiple choice question has been scrambled)
  45. What is a precursor step to the Krebs cycle and oxidative phosphorylation that produces some quantity of ATP and does not occur in the mitochondria.
  46. What contains pigment and functions in photosynthesis as well as in other cellular processes and are found almost solely in plant cells?
  47. The most abundant of the plastids are what?
    Chloroplasts, which contain the green pigment chlorophyll
  48. Autolysis refers to the process by which the cell digests its own structures. Cell death allows the release of material normally sequestered within membrane-bound enclosures. The release of these materials brings on autolysis. Which of the following organelles most likely releases the substances that mediate autolysis?
    A. Vacuole
    B. Mitochondrion
    C. Lysosome
    D. Plastid
    C. The question calls for the cellular organelle that harbors degradative enzymes. Lysosomes contain hydrolytic enzymes that, among other things, digest senescent cellular components.
    (this multiple choice question has been scrambled)
  49. Which of the following organelles plays the most direct role in the maintenance of concentration gradients across the cell membrane?
    A. Smooth endoplasmic reticulum
    B. Mitochondrion
    C. Golgi apparatus
    D. Vesicle
    B. Maintaining a concentration gradient requires the expenditure of energy. ATP, which serves as the source of energy for this and other active processes, is synthesized in the mitochondria.
    (this multiple choice question has been scrambled)
  50. What are chromosomes?
    They are composed of DNA (deoxyribonucleic acid) and proteins, bear the cell's genetic material and reside within the nucleus.
  51. The nucleus is surrounded by a double membrane called the _______ _______. Throughout the membrane are _______ _____ which selectively allow the transportation of large particles to and from the nucleus. DNA can be found within the nucleus as ________ (DNA complexed to proteins like histones) or as __________ which are more clearly visible in a light microscope. The ____________ is not membrane bound. It contains the DNA necessary to synthesize ____________ RNA.
    nuclear envelope; nuclear pores; chromatin; chromosomes; nucleolus; ribosomal
  52. What is the nucleolus?
    Located in the nucleus, a suborganelle that is the site of formation of ribosomal ribonucleic acid (rRNA), which functions in the translation of the genetic code.
  53. What are cilia and flagella?
    They are associated with cellular locomotion, but depending on the cell site, they may serve other functions.  A flagellum is a whip-like organelle of locomotion found in sperm. Cilia are hair-like vibrating organelles which can be used to move particles along the surface of the cell (i.e. in the fallopian tubes cilia can help the egg move toward the uterus)
  54. What are microtubules?
    They are the structural basis of the cilia and flagella. They are also the main component of centrioles. They are also found in the cytoplasm, where they serve as a quasiskeletal structure for the cell itself (cytoskeleton). They are principally formed of a protein termed tubulin.
  55. When does the centriole function?
    They are cylinder-shaped complexes of microtubules associated with the mitotic spindle.The centriole functions during cell division, assisting in the formation of the mitotic spindle. At the base of flagella and cilia, two centrioles can be found at right angles to each other; this is called a basal body.
  56. What are microfilaments?
    They are also found in the cytoplasm and serve as a second element of the cytoskeleton. Microfilaments are composed of the protein actin. They also function in cellular movement.
  57. All of the following structures contain microtubules EXCEPT:
    A. cilia.
    B. the nucleolus.
    C. the cytoskeleton.
    D. the mitotic spindle.
    B. There are multiple functions performed by the microtubules and they are largely composed of the protein tubulin. Single or in groups, microtubules provide the cell and some cell components with form and rigidity. They form the structural basis of the cytoskeleton, cilia, flagella, and the mitotic spindle.
    (this multiple choice question has been scrambled)
  58. Microtubules and microfilaments are composed primarily of:
    A. protein.
    B. lipopolysaccharide
    C. carbohydrate.
    D. phospholipid.
    A. Microtubules are composed of the protein tubulin, and microfilaments of the protein actin.
    (this multiple choice question has been scrambled)
  59. In chronic obstructive pulmonary disease (COPD), the patient suffers, among other difficulties, and inability to expel mucosal secretion from the airway. Which cellular component is most likely dysfunctional?
    A. The cilia
    B. The mitotic spindle
    C. The nucleolus
    D. The centriole
    A. Cilia may participate in the cellular locomotion and, depending on the site of the cells on which they are located, other functions as well. In the human airway, they serve to remove secretions and thus to keep the airway free of obstruction. The nucleolus is located in the nucleus and is the site of the formation of rRNA; the centriole functions in the formation of the mitotic spindle.
    (this multiple choice question has been scrambled)
  60. The plasma membrane is a semipermeable barrier that defines the outer perimeter of the cell. It contains phospholipids which are _______, their tail end that is repelled from a mass of water, which is ________, the opposite end which contains a charged phosphate head which is soluble in water, or _________).
    amphipathic; hydrophobic; hydrophilic
  61. The phospholipids of the cell membrane are fluid and thus...
    move freely from place to place in the membrane.
  62. Because there are a limited amount of carriers, if the concentration of solute is too high, the carriers would be __________, and the rate of crossing the membrane would _______ _____ (saturation kinetics).
    saturated; level off
  63. What process is shown by the following:Image Upload
    Simple Diffusion: the greater the concentration gradient, the greater the rate of transport across the plasma membrane
  64. What process is shown by the following:Image Upload
    Carrier-Mediated Transport: increasing the concentration gradient increases the rate of transport until a maximum rate at which all membrane carriers are saturated. There is some sort of channel or protein that moves from the higher concentration to the lower concentration. (Like proteins, large and negatively charged)
  65. The two carrier-mediated transport systems are:
    facilitated transport and active transport
  66. Cytoskeleton extends throughout the entire cell and has particular importance in shape and intracellular ______________. It also makes extracellular complexes with other ________ forming a matrix so that the cells can "stick" together.
    • transportation
    • proteins
  67. __________ __________ and __________ extend along axons and dendrites of neurons acting like railroad tracks so organelles or protein particles can shuttle to or from the cell body.
    Intermediate filaments and microtubles
  68. What are the regularly arranged finger-like projections with a core of cytoplasm called and where are they commonly found?
    Microvilli; in the small intestine where they help increase the absorptive and digestive surfaces (brush border).
  69. What is heterolysis?
    heterolysis refers to the process of programmed cell death induced by hydrolytic enzymes from surrounding (usually inflammatory) cells
  70. Which contains the genetic information of the cell? DNA or RNA
  71. From what is a nucleotide composed?
    Also called a nucleoside phosphate, it is composed of a five carbon sugar, a nitrogen base, and an inorganic phosphateImage Upload
  72. What are the two categories of nitrogen bases?
    purines and pyrimidines
  73. What is the backbone of each helix?
    2-deoxyribose phosphates - sugar-phosphate backbone
  74. The nitrogen bases project to the center of the double helix in order to ________ _____ with each other.
    hydrogen bond (imagine the double helix as a winding staircase: each stair would represent a pair of bases binding to keep the shape of the double helix intact)
  75. There is specificity in the binding of the bases of DNA: one _____ binds one pyrimidine. In fact, adenine only binds with _______ (through _____ hydrogen bonds) and guanine only binds with ________ (through ____ hydrogen bonds). The more the H-bonds, the more stable the helix will be.
    purine; thymine; two; cytosine; three
  76. The replication (duplication) of DNA is semi-conservative. What does this mean?
    Each strand of the double helix can serve as a template to generate a complementary strand.
  77. For each double helix, there is an old strand and a new strand. What are these called?
    There is one parent strand (old) and one daughter strand (new)
  78. When does DNA synthesis occur?
    It occurs in the S stage of interphase during the cell cycle.
  79. At what positions does each nucleotide have a hydroxyl or phosphate group?
    At the 3rd and 5th carbons designated the 3' and 5' positionsImage Upload
  80. What kind of bonds can be formed between the 3' hydroxyl group and a free 5' phosphate group?
    Phosphodiester bonds
  81. In what direction does DNA polymerization occur? Since DNA is wound together in a double helix, DNA replication is ____-_________ which the 5'-3' being the _____ strand and the 3'-5' being the _____ strand.
    • DNA polymerase can add free nucleotides only to the 3' end of the template strand. This results in elongation of the newly forming strand in a 5'-3' direction.
    • Semi-discontinuous
    • Leading
    • Lagging
  82. How long (approximately) does the cell cycle take? What is synthesized during this time?
    • approximately 18-22 hours
    • New DNA is synthesized and partitioned equally so that division can then occur.
  83. What are the phases of the cell cycle?
    • Interphase (G1 [also called gap phase], S [also called the synthesis phase], G2 [also called the growth phase]) and
    • Mitosis (prophase, metaphase, anaphase and telophase.Image Upload
  84. Give the stages of mitosis (in order).
    prophase, metaphase, anaphase, and telophase [Mnemonic for the sequence of phases: P. MATI]
  85. What percentage of the cell cycle is the interphase and what occurs during this phase?
    about 90%, the cell prepares for DNA synthesis (G1), synthesizes or replicates DNA (S), and ultimately begins preparing for mitosis (G2)
  86. The cell-cycle phase associate with the replication of the cell's genome is:
    A. the G2 period of interphase.
    B. the S phase of interphase.
    C. cytokinesis.
    D. mitosis.
    B. The cell's genome is replicated during the S phase of the cell cycle. The G2 portion of interphase represents the second gap phase. Mitosis involves nuclear division. Cytokinesis refers to the division of the cytoplasm (as opposed to the division of the nucleus).
    (this multiple choice question has been scrambled)
  87. Sister chromatids are:
    A. unrelated to one another.
    B. identical to one another.
    C. produced during the G1 phase of the cell cycle.
    D. homologous to one another.
    B. Sister chromatids are produced through DNA replication and are therefore identical to one another. They are produced during the S phase, not the G1 phase.
    (this multiple choice question has been scrambled)
  88. What is prophase in mitosis?
    • During prophase, the chromosomes condense to the point that they are visible under the light microscope as an X-shaped structure. Pairs of centrioles migrate away from each other (to opposite poles of the cell) while microtubules appear in between forming a spindle. Other microtubules emanating from the centrioles give a radiating star-like appearance; thus they are called asters. Therefore, centrioles form the core of the Microtubule Organizing Centers (MTOC). Simultaneously, the diffuse nuclear chromatin condenses into the visible chromosomes which consist of two identical sister chromatids. The area of constriction where the two chromatids are attached is the centromere. Ultimately, the nuclear envelope disappears at the end of prophase.
    • Image Upload
  89. What are the terms for the center and the ends of the chromosome?
    The area of constriction where the two chromatids are attached it the centromere and the ends are referred to as the telomereImage Upload
  90. What is the metaphase in mitosis?
    • This is when the centromeres line up along the equatorial plate. At or near the centromeres are the kinetochores which are proteins that face the spindle poles (asters). Microtubules, from the spindle, attach to the kinetochores of each chromosome. The kinetochore fibers help to align and maintain the chromosomes on the metaphase plate.
    • Image Upload
  91. What is the anaphase in mitosis?
    • Sister chromatids are pulled apart (as a result of the splitting of the centromere) such that each migrates to opposite poles being guided by spindle microtubules. With the separation of the sister chromatids, each chromatid is called a daughter chromosome. Cytokinesis begins during the last part of anaphase.
    • Image Upload
  92. What is telophase in mitosis?
    The daughter chromosomes are positioned at opposite poles of the cell and the kinetochore fibers disappear. New membranes (a nuclear membrane) form around the daughter nuclei; nucleoli reappear; the chromosomes uncoil (decondense) and become less distinct and are no longer visible by light microscopy; and finally, cytokinesis (cell separation) occurs.Image Upload
  93. Development of a cleavage furrow occurs during:
    A. interphase.
    B. cytokinesis.
    C. metaphase.
    D. prophase.
    B. The cleavage furrow develops around the periphery of the cell toward late anaphase or early telophase. However, the development of the cleavage furrow is the beginning of cytokinesis, which makes cytokinesis the best answer. It initiates the division of the parent cell into two daughter cells. The daughter cells normally receive approximately equal amounts of cytoplasm and an equal inventory of organelles.
    (this multiple choice question has been scrambled)
  94. Which of the following stages involve(s) a change in chromosome density?
    A. Anaphase and telophase
    B. Prophase and telophase
    C. Prophase alone
    D. Interphase alone
    B. At prophase, the chromosomes condense and become visible under the light microscope. At telophase, the process is reversed: Chromosomes decondense and disappear.
    (this multiple choice question has been scrambled)
  95. What is Interphase in mitosis?
    • The last of the sequence of phases of the cell cycle. It is the phase of the cell cycle in which the cell spends the majority of its time and performs the majority of its purposes including preparation for cell division. In preparation for cell division, it increases its size and makes a copy of its DNA, which is made during the S phase. Interphase does not describe a cell that is merely resting but is rather an active preparation for cell division.
    • Image Upload
  96. What is the minimum number of membranes you cross from the outside of the cell to the inside of the nucleus?
    3-the cell has a membrane, and the nucleus has a double-membrane (two).
  97. What is the minimum number of lipid layers you cross from the outside of the cell to the inside of the mitochondria?
    6 - the cell membrane has a phospholipid bilayer (two), the mitochondria are double-membrane organelles, each has a bilayer also so each one would be another two layers of lipids. 2+2+2=6
  98. In what phase would a drug that arrests the development of the cytoskeletal-elements act?
  99. Describe what is within the human somatic cell nucleus.
    Within the human somatic cell nucleus are 46 chromosomes organized into 22 pairs of homologous chromosomes (or autosomes) and either 1 pair of hemizygous (found in males only) sex chromosomes or 1 pair of homologous sex chromosomes.
  100. What is reduction division?
    Meiosis: reduction division refers to the generation of haploid daughter cells by a diploid parent cell. Reduction division is accomplished by meiosis and is the basis of gametogenesis.
  101. Describe the stages of meiosis.
    Like mitosis, meiosis involves nuclear division and cytokinesis. Nuclear division in meiosis embodies four stages: prophase, metaphase, anaphase, and telophase, however, meiosis involves two divisions (or two cycles) instead of one. So, meiotic division of the first cycle is: prophase I, metaphase I, anaphase I, and telophase I; the second is prophase II, metaphase II, anaphase II, and telophase II.
  102. Chromotids may break at the chiasma. When this happens, the resulting segments may change places with one another in what process?
    A process called crossing over. Crossing over produces a physical exchange of chromatid segments between sections of homologous chromatids.
  103. The proximity between homologous  chromosomes during synapsis frequently leads chromatids from one homologue to physically bind with chromatids from the other homologue. What is the site at which binding occurs called?
    The chiasma or synaptonemal membrane.
  104. Which of the following is associate with meiotic prophase I but not with mitotic prophase?
    A. Condensed chromosomes
    B. Movement of centrioles to opposite cellular poles
    C. Spindle formation
    D. Tetrad formation
    D. is correct.
    (this multiple choice question has been scrambled)
  105. Which of the following most completely characterizes the process of crossing over?
    A. Duplicated chromosomes pair with their duplicated homologues.
    B. A nuclear division during which each daughter cell receives the genetic material from only one chromosome of each homologous pair.
    C. Genetic material is exchanged between homologous chromosomes during synapsis.
    D. A chiasma is formed.
    C. is correct.
    (this multiple choice question has been scrambled)
  106. Which of the following correctly distinguishes mitosis from the first division of meiosis?
    A. After the first meiotic division, each daughter cell possesses chromosomes that are organized into tetrads; after meiosis, they do not.
    B. After mitosis, each daughter cell possesses a full complement of genetic material; after the first meiotic division, they do not.
    C. After mitosis, each daughter cell posses duplicated chromosomes; after meiosis, they do not.
    D. After the first meiotic division, each daughter cell posses a full complement of genetic material; after mitosis, they do not.
    B. The daughter cells produced by the first meiotic division do not have a full complement of genetic material. Because homologues separate while their centromeres remain intact, each daughter cell receives only one member of each homologous chromosomal pair. They absence of the other member of the homologous pair means that each daughter receives half of the full parental genome. Each of the daughter cells produce by mitosis, on the other hand, receives one copy of each member of each chromosome; it receives the full parental genome.
    (this multiple choice question has been scrambled)
  107. After meiotic division is fully completed, how many daughter cells are produced from one parent? And how does this differ from mitosis?
    Mitosis generates two diploid daughters. In meiosis, a total of four daughter cells are produced and each is haploid.
  108. How does meiotic metaphase I differ from mitotic metaphase?
    It differs in that pairs of homologous chromosomes (instead of single chromosomes) align on the spindle apparatus. That is, tetrads (composed of four chromatids) align along the spindles. By comparison, in mitotic metaphase a double-stranded chromosome composed of two sister chromatids aligns on the metaphase plate.
  109. Crossing over causes what to happen?
    Causes each chromatid to lose a component of its own DNA and to acquire in it s place a corresponding section of DNA from  its homologue. Crossing over, therefore, is a form of genetic recombination that is specific to meiosis.
  110. How does prophase I differ from mitotic prophase?
    It differs in that homologous pairs of duplicated chromosomes align in proximity to one another, forming tetrads. The association of homologous pairs of duplicated chromosomes to form the tetrad is termed synapsis.
  111. Describe the meaning of the word gametogenesis.
    This refers to the generation of gametes through meiosis. More specifically, spermatogenesis denotes the formation of the sperm cell, which is the male gamete, and oogenesis denotes the formation of the ovum, which is the female gamete.
  112. Which of the following correctly orders the structures through which sperm cells travel?
    A. Epididymis, vas deferens, ejaculatory duct, seminiferous tubule, urethra
    B. Vas deferens, epididymis, ejaculatory duct, seminiferous tubule, urethra
    C. Seminiferous tubule, epididymis, vas deferens, ejaculatory duct, urethra
    D. Ejaculatory duct, seminiferous tubule, vas deferens, epididymis, urethra
    C. Newly formed spermatozoa travel first through the seminiferous tubule, then through the epididymis, then through the vas deferens, the ejaculatory duct, and the urethra. A flagellum affords a sperm cell the motility it needs to reach the ovum, and acrosomal enzymes assist it in penetrating the ovum during fertilization.
    (this multiple choice question has been scrambled)
  113. Which of the following describes an entity that is haploid?
    A. Embryo
    B. Zygote
    C. Spermatogonium
    D. Spermatid
    D. Spermatogenesis begins with the spermatogonium, at diploid cell. After it enlarges and undergoes replication of its genome, it becomes a primary spermatocyte in which chromosomes have doubled, but are still joined at a centromere. According to current terminology, therefore, each primary spermatocyte is said to have twenty-three chromosomal pairs (not forty-six pairs), with each member of each pair being joined at a centromere to a sister chromatid.
    (this multiple choice question has been scrambled)
  114. What is the diploid cell called that begins the process of meiosis in the ovary? What is produced from it?
    Oogonium; primary oocyte
  115. How does the first meiotic division of the primary oocyte differ from the first meiotic division that accompanies spermatogenesis?
    Unlike the first meiotic division that accompanies spermatogenesis, this division divides cytoplasm unequally between the progeny, producing one larger and one smaller daughter cell. The larger one is called a secondary oocyte and the smaller a polar body.
  116. What are the net products of oogenesis?
    Two or three small haploid polar bodies, which degenerate, and one large haploid ovum.
  117. Which of the following correctly orders the cell types that arise during oogenesis?
    A. Primary oocyte, secondary oocyte, oogonia, ovum
    B. Ovum, primary oocyte, secondary oocyte, oogonia
    C. Secondary oocyte, primary oocyte, oogonia, ovum
    D. Oogonia, primary oocyte, secondary oocyte, ovum
    D. The undifferentiated oogonium becomes the primary oocyte, which produces secondary oocytes and then the ovum. In the course of oogenesis, as many as three polar bodies are generated.
    (this multiple choice question has been scrambled)
  118. Which of the following does NOT apply to a polar body?
    A. It is small in relation to an ovum.
    B. It arises as a by-product of oogenesis.
    C. It is diploid.
    D. It degenerates.
    C. Meiosis generates four haploid cells from one diploid cell. In the case of oogenesis, the first meiotic division allocates cytoplasm unequally, yielding two progeny of unequal size. The small of the two is a polar body. The larger progeny undergoes a second meiotic division that yields a relatively large ovum and a relatively small polar body, both haploid. The polar bodies degenerate.
    (this multiple choice question has been scrambled)
  119. Which of the following correctly distinguishes spermatogenesis from oogenesis?
    A. Spermatogenesis produces four functional gametes; oogenesis does not.
    B. Spermatogenesis produces a gamete; oogenesis does not.
    C. Spermatogenesis occurs in the gonads; oogenesis does not.
    D. Spermatogenesis yields haploid cells; oogenesis does not.
    A. is correct.
    (this multiple choice question has been scrambled)
  120. Which of the following is a false statement?
    A. The placenta functions to exchange wastes and nutrients between the embryo and the mother.
    B. Enzymes derived from the acrosome of the sperm facilitate the sperm's penetration of the zona pellucida and corona radiate.
    C. The site of implantation is the uterine wall.
    D. The site of fertilization is the uterus.
    D. is correct.
    (this multiple choice question has been scrambled)
  121. How does the prokaryotic cell's (bacterium) genome differ from the eukaryotic cell's?
    The genome is also composed of double stranded DNA, but there is only one highly coiled, circular chromosome, which is not enclosed in a membrane or nucleus.
  122. Within the normal human somatic cell nucleus, there are:
    A. twenty-three chromosomes composed of deoxyribonucleic acid.
    B. forty-six chromosomes composed of deoxyribonucleic acid.
    C. twenty-three pairs of genes embodied within the chromosomes.
    D. forty-six genes embodied within chromosomes.
    B. Every normal human somatic cell (meaning cells other than the gametes) has 46 chromosomes (twenty-three pairs) in the nucleus.
    (this multiple choice question has been scrambled)
  123. DNA molecules fit within the eukaryotic cell nucleus because they are wrapped and coiled. What are they wrapped around?
    They wrap themselves in a complicated arrangement around packaging proteins called histones.
  124. Near the time of cell division, the chromosomes wrap around their histones in a highly condensed form that makes the histones visible as discrete units that resemble beads on a string. What are the visible units of histone called?
  125. Histones allow for:
    A. efficient packaging of the nucleolus.
    B. proper reproduction of chromosomes.
    C. mixing of genetic information between and among gene segments.
    D. enzyme synthesis within the nucleus.
    B. The cells of complex organisms, such as those of humans, have very long chromosomes. In order for the chromosomes to physically fit within the nucleus and to undergo accurate reproduction, they must be packed efficiently.
    (this multiple choice question has been scrambled)
  126. Histones are composed of:
    A. base pairs.
    B. ribonucleic acid.
    C. nitrogen and phosphate.
    D. protein
    D. Histones are proteins around which deoxyribonucleic acid is wrapped in its complex packaging structure. Histones are the protein component of the chromosome.
    (this multiple choice question has been scrambled)
  127. Nucleosome refers to:
    A. visible units of nucleotide bases.
    B. visible units of histone protein.
    C. functional units of nuclear membrane.
    D. functional units of the nucleolus.
    B. Just prior to cell division, the eukaryotic cell's chromosomes wrap themselves tightly around their associated histone proteins.
    (this multiple choice question has been scrambled)
  128. What are the backbone strands of DNA made from?
    It is alternating units of deoxyribose (a sugar or carbohydrate) and phosphate bound by phosphodiester bonds.
  129. What is running between opposing units on each strand?
    Pairs of nitrogenous heterocyclic bases (one base attached to each strand). Each base, attached to a sugar and phosphate group, is a nucleotide.
  130. The DNA molecule features four different nitrogenous bases. Name them.
    • adenine (A) - a purine
    • cytosine (C) - a pyrimidine
    • guanine (G) - a purine
    • thymine (T) - a pyrimidine

    • Memory tool:
    • Pure Ag (silver element symbol) --> the purines are Adenine and Guanine 

    You CUT a "pye": the pyrimidines are Cytosine, Uracil (in RNA), and Thymine
  131. On one strand of a DNA molecule, units of the sugar-phosphate backbone are bound together by:
    A. phosphodiester bonds.
    B. hydrogen bonds.
    C. noncovalent bonds.
    D. dipole-dipole interactions.
    A. The DNA strand backbone is made of alternating units of deoxyribose and phosphate, bound together by a phosphodiester bond. Phosphodiester bonds are covalent and are not an example of dipole-dipole interactions. Hydrogen bonds do function in holding nucleotide base pairs together, but they do not serve directly in the structure of the sugar-phosphate backbone.
    (this multiple choice question has been scrambled)
  132. When adenine and thymine pair, how many hydrogen bonds form to join them? How many between guanine and cytosine?
    A-T have two pairs of hydrogen bonds, while G-C have three pairs.
  133. If a DNA molecule had the following nucleotide sequence, give the other deoxyribose-phosphate strand of that same DNA molecule with the complementary nucleotide sequence:
    (5') -T A G T G- (3')
    (3') -A T C A C- (5')
  134. Adenine and guanine are:
    A. histones.
    B. nucleosomes.
    C. pyrimidines.
    D. purines.
    D. is correct.
    (this multiple choice question has been scrambled)
  135. Which of the following represents a correct base pairing within a DNA molecule?
    A. Cytosine - thymine
    B. Adenine - guanine
    C. Thymine - Adenine
    D. Adenine - cytosine
    C. is correct.
    (this multiple choice question has been scrambled)
  136. Matched bases within a base pair are linked by:
    A. nonpolar covalent bonds.
    B. hydrogen bonds.
    C. polar covalent bonds.
    D. ionic bonds.
    B. Within the DNA molecule, matched bases are linked by hydrogen bonds. Although these are not as strong as any of the other bonds listed in the answer choices, their large number affords the DNA molecule significant structural integrity and support.
    (this multiple choice question has been scrambled)
  137. Which of the following is true of DNA in a double helix?
    A. It consists of two complementary strands.
    B. It is composed of phospholipid.
    C. It is devoid of carbohydrate.
    D. It is single-stranded.
    A. is correct.
    (this multiple choice question has been scrambled)
  138. If one strand of a DNA molecule shows the base sequence (5') -A G A T - (3'), its complementary strand will show the sequence:
    A. (5') -A T C T- (3')
    B. (5) -A G A A- (3')
    C. (5') -A T C C- (3')
    D. (5') -G T T C- (3')
    A. Conceptually, it is (3') -T C T A- (5') but if we wish to describe the daughter strand in conventional fashion, it would be ordered in the 5' to 3' direction.
    (this multiple choice question has been scrambled)
  139. The variable region of a DNA molecule carries:
    A. deoxyribose.
    B. nucleosomes.
    C. histones.
    D. purines and pyrimidines.
    D. is correct.
    (this multiple choice question has been scrambled)
  140. Which of the following properly describes the antiparallel structure of a DNA molecule?
    A. Each complementary strand has a 3' carbon at its bottom end and a 5' carbon at its top end.
    B. Complementary strands show opposite orientation in terms of their 3' and 5' carbon ends.
    C. Complementary strands will not bond unless bases are matched purine to purine and pyrimidine to pyrimidine.
    D. Base-pairing rules require that purines pair with pyrimidines and pyrimidines with purines.
    B. Antiparallelism refers to the orientation of the two sugar-phosphate backbones with respect to each other in a DNA molecule.
    (this multiple choice question has been scrambled)
  141. DNA replication begins at the Origin of Replication (or Ori). What is this?
    a specific sequence of nucleotides that are the signal to start DNA synthesis.
  142. To begin DNA replication, first, the DNA strands must be unwound. This is facilitated by what?
    helicase enzymes
  143. What is a replication bubble?
    The two deoxyribose-phosphate strands do not fully separate before daughter strands begin to form. Rather, they partially diverge at what is called a replication bubble, which has two replication forks.
  144. Synthesis of the new DNA strand is accomplished by a family of enzymes. What are they called?
    In order to begin synthesis, these enzymes require a primer. What is it called?
    DNA polymerases; an enzyme named primase
  145. Why is replication said to be semiconservative?
    because each of the newly formed molecules contains half of the original DNA molecule
  146. DNA polymerases synthesize DNA in one direction only. What direction is that?
    5' to 3' - a newly growing nucleotide chain does NOT take on new nucleotide units at its 5' end, but rather at its 3' end.
  147. What is the polarity problem of DNA synthesis?
    The replication fork is opening one direction and DNA can only be synthesized in the opposite direction. The only way around this is to synthesize the new DNA is fragments called Okazaki fragments that constitute the lagging strand.
  148. How are the fragments of the lagging strand of DNA synthesis joined?
    with DNA ligase to generate a continuous DNA strand.
  149. Give a summary of DNA replication steps.
    1. What is recognized on the DNA strand?
    2. How are the stands separated?
    3. What is formed with two replication forks?
    4. What lays down RNA primers?
    5. What read the template strand in the 3' to 5' direction and synthesized a new complementary strand?
    6. What fragments of the lagging strand are joined and what joins them?
    7. What then happens to the RNA primers?
    • 1. The Ori is recognized on the DNA strand.
    • 2. The DNA strands are separated via helicase.
    • 3. A replication bubble is formed, with two replication forks.
    • 4. RNA primers are laid down by primase.
    • 5. DNA polymerases read the template strand (in the 3' to 5' direction) and synthesizes a new complementary strand (in the 5' to 3' direction). This can occur in a continuous way (as in the leading strand) or via a semidiscontinuous mechanism (as in the lagging strand).
    • 6. Okazaki fragments of the lagging strand are joined by DNA ligase.
    • 7. The RNA primers are removed and replaced with DNA (this is done by DNA polymerases).
  150. DNA polymerases catalyze:
    A. the synthesis of pyrimidines.
    B. addition of a nucleotide residue at the 5' end of a growing chain of nucleotide residues.
    C. addition of a nucleotide residue at the 3' end of a growing chain of nucleotide residues.
    D. the synthesis of purines.
    C. is correct.
    (this multiple choice question has been scrambled)
  151. The need for semidiscontinuous synthesis of one DNA daughter strand arises because of the:
    A. pairing phenomena associated with purines and pyrimidines.
    B. hydrogen bonding between nucleotide base pairs.
    C. antiparallel orientation of the two parents.
    D. ability of DNA polymerases to ad nucleotides to the 3' end or 5' end of growing DNA polymer.
    C. is correct.
    (this multiple choice question has been scrambled)
  152. With regard to DNA replication, the term template refers to the:
    A. phosphodiester bonding that secures the sugar phosphate backbone of a new DNA molecule.
    B. role of the parent strand in directing formation of a new complementary strand.
    C. elongation of a growing DNA strand.
    D. role of enzymes in unwinding the molecule to be replicated.
    B. is correct.
    (this multiple choice question has been scrambled)
  153. Synthesis of a daughter DNA strand is facilitate most directly by:
    A. a phospholipid-protein backbone.
    B. a polymerase enzyme.
    C. a helicase enzyme.
    D. a cleaving enzyme.
    B. DNA polymerases synthesize the daughter DNA strands by reading the parental templates.
    (this multiple choice question has been scrambled)
  154. With respect to chromosomal replication, a replication fork represents:
    A. the creation of Okazaki fragments that oppose the synthesis of nucleotide chains in the 5' to 3' direction.
    B. divergence of two parent strands, each of which then serves as a template for the creation of a new daughter strand.
    C. the joining of two parent strands to create a single new daughter strand.
    D. a catalytic addition of nucleotide units to the 5' end of a newly developing daughter strand.
    B. is correct.
    (this multiple choice question has been scrambled)
  155. Okazaki fragments:
    A. cannot be incorporated into newly forming daughter strands.
    B. facilitate semidiscontinuous synthesis on the lagging strand.
    C. are synthesized in the 3' to 5' direction.
    D. contain neither purines nor pyrimidines.
    B. is correct.
    (this multiple choice question has been scrambled)
  156. In conventional fashion, describe the nucleotide sequence of a daughter strand that follows from a template bearing this nucleotide sequence:
    (5') -T A G C G G T T A- (3')
    (5') -T A A C C G C T A- (3') or simply, T A A C C G C T A
  157. DNA has deoxyribose (it lacks OH on the 2' carbon of ribose) as the sugar of its backbone. What does RNA use?
    Ribose (it has an OH on the 2' carbon of ribose)
  158. DNA has cytosine and thymine as its pyrimidines. What pyrimidines are used in RNA?
    cytosine and uracil
  159. Describe the typical strands of DNA vs RNA, as well as the stability difference and lifespan in the cell.
    DNA usually is double-stranded (except in some viruses) and RNA is usually single-stranded. DNA is more stable while RNA is less stable. DNA is permanent and RNA has a transient lifespan in the cell.
  160. What are the three predominant types of RNA?
    ribosomal RNA (rRNA), transfer RNA (tRNA), and messenger RNA (mRNA)
  161. How is transcription different from DNA replication?
    Both begin with separating the DNA's strands. In transcription, one of the strands serves as a template for the synthesis of an RNA molecule with the same base pairing except uracil is used in place of thymine.
  162. DNA strands are given names during transcription. List and give a description of each.
    The one that serves as a template and is actually read and transcribed is called the template, the non-coding strand, or the anti-sense strand. The other strand that does not serve as template is called the coding strand or sense strand.
  163. In transcription, formation of an RNA polymer is catalyzed by enzymes called what?
    RNA polymerases. As the DNA polymerases do, RNA polymerases add nucleotides to the 3' end of the growing chain. Therefore, the template DNA is red in the 3' to 5' direction and the new nucleic acid molecule is synthesized in the 5' to 3' direction.
  164. Among the similarities between DNA and RNA are that both molecules:
    A. include the sugar deoxyribose.
    B. are ordinarily double-stranded.
    C. are formed from DNA templates.
    D. include the pyrimidine thymine.
    C. is correct.
    (this multiple choice question has been scrambled)
  165. What is the nucleotide sequence for an mRNA molecule transcribed from a DNA template with this nucleotide sequence:
    (5') -T A G C G G C C A T- (3')
    • Expressed in conventional terms:
    • (5') -A U G G C C G C U A- (3')
  166. If the process of transcription creates an RNA polymer with nucleotide sequence (5') -G A U U G G C A A C- (3'), the coding strand of DNA (expressed in the conventional 5' to 3' direction) has the nucleotide sequence:
    A. (5') -G A T T G G C A A C- (3')
    B. (5') -C A A C G G U U A G- (3')
    C. (5') -G A U U G G C A A C- (3')
    D. (5') -C A A C G G T T A G- (3')
    A. The non-coding, or template, DNA strand would be (3') -C T A A C C G T T G- (5'), so the coding strand of DNA would be as given in the answer.
    (this multiple choice question has been scrambled)
  167. Transcription differs from DNA replication in that transcription:
    A. produces a single-stranded end product.
    B. does not involve base-pairing between purine and pyrimidine residues.
    C. involves chain elongation in the 5' to 3' direction.
    D. does not involve base-pairing between cytosine and guanine residues.
    A. is correct.
    (this multiple choice question has been scrambled)
  168. Give the 4 steps (phases) of prokaryotic transcription.
    • 1. template recognition
    • 2. initiation
    • 3. elongation
    • 4. termination
  169. What is upstream and downstream when used in reference to RNA?
    Upstream points towards the 5' and downstream points towards the 3' of the coding strand.
  170. The phrase "consensus sequence" refers to the fact that:
    A. the Pribnow box is absent in most prokaryotic cells.
    B. in prokaryotes, one subunit of RNA polymerase is detachable, even though it is essential to chain elongation.
    C. prokaryotes tend to show significant commonality in some of the nucleotide presented at their DNA promoter sites.
    D. prokaryotes and eukaryotes produce mRNA via the process of transcription, even though prokaryotic RNA is double-stranded.
    C. The consensus sequences (the sequence TATAAT, called the Pribnow box, at or near the -10 position, and TTGACA at or near the -35) are called that because many diverse species of bacteria have achieved some "consensus" on what nucleotide sequences they will present at these two locations of their promoter sites.
    (this multiple choice question has been scrambled)
  171. The initiation phase of transcription is complete when:
    A. a first phosphodiester bond is formed between two nucleotide residues on a newly forming RNA polymer.
    B. RNA polymerase loses its sigma factor.
    C. a first RNA nucleotide residue is hydrogen bonded to its counterpart on a DNA molecule.
    D. DNA and RNA forma a hybrid.
    B. is correct.
    (this multiple choice question has been scrambled)
  172. Give the processes in order of the initiation phase of transcription.
    1. What approaches the DNA template?
    2. What bonds form between RNA nucleotide residues and DNA nucleotide residues to form the DNA-RNA hybrid?
    3. What catalyzes the formation of a phosphodiester bond?
    4. What are added to the growing chain?
    5. When the chain is about how long, the _____ ______ detaches from RNA polymerase and initiation is complete?
    • 1. two ribonucleoside triphosphates (or nucleotides) approach the DNA template;
    • 2. temporary hydrogen bonds form between RNA nucleotide residues and DNA nucleotide residues to form a DNA-RNA hybrid;
    • 3. RNA polymerase catalyzes the formation of a phosphodiester bond between the two nucleotide residues, and a pyrophosphate is released;
    • 4. additional ribonucleoside triphosphates are added to the growing chain, and additional phosphodiester bonds are formed;
    • 5. when the growing chain is about nine nucleotide residues in length, the sigma factor detaches from RNA polymerase, and initiation is complete.
  173. During transcription, which of the following events is earliest to occur?
    A. Location of ribonucleoside triphosphates at the start site.
    B. Phosphodiester bond formation.
    C. Binding of enzyme to a DNA molecule.
    D. Local disassembly of the DNA's double helical structure.
    C. is correct.
    (this multiple choice question has been scrambled)
  174. The first event of transcription is binding of RNA polymerase to a promoter site located on the DNA molecule. What are the next three steps?
    • local unwinding of the DNA double helix;
    • positioning of two nucleotide units, bound within ribonucleoside triphosphates at the start site, according to the base-pairing rules; and
    • the formation of a phosphodiester bond between the 3' end of the first nucleotide residue and the 5' end of the second
  175. Which of the following events does not occur during the elongation phase of transcription?
    A. Addition of nucleotides to the 3' end of a growing RNA polymer
    B. Pairing of purines with pyrimidines
    C. Elongation of an RNA polymer in the 5' to 3' direction
    D. Movement of DNA polymerase along a DNA template
    D. The polymerization of RNA is catalyzed not by DNA polymerase, but by RNA polymerase. Choice A describes an event that occurs in DNA replication, not transcription.
    (this multiple choice question has been scrambled)
  176. The combination of a _______ _____ and ruptured uracil-adenine RNA-DNA hybrid is one means by which RNA synthesis terminates in bacteria. Another termination method uses the action of an ATP-dependent enzyme called the ____ ______.
    hairpin loop (a length of RNA that is rich in GC sequences and is able to fold in on itself and form a loop that base-pairs within itself); rho factor
  177. Which of the following events does not take place within the transcription bubble?
    A. Rewinding of the DNA double helix
    B. Reattachment of the sigma factor to create a holoenzyme
    C. Formation of a DNA-RNA hybrid
    D. Unwinding of the DNA double helix
    B. The RNA polymerase sigma factor detaches at the end of initiation, but it does not reattach during elongation. It reattaches after termination of transcription, when RNA polymerase is released from the DNA template.
    (this multiple choice question has been scrambled)
  178. If the prokaryotic transcription process ends via hairpin loop, it is most likely that:
    A. guanine residues will be absent from any region near the 3' end of the newly formed RNA molecule.
    B. cytosine residues will be absent from all regions near the 3' end of the newly formed RNA molecule.
    C. the rho factor will be absent from the termination process.
    D. uracil residues will be absent from all regions near the 3' end of the newly formed RNA molecule.
    C. The hairpin loop and the rho factor generally represent two alternative means by which prokaryotic transcription terminates.
    (this multiple choice question has been scrambled)
  179. The word prokaryote is largely synonymous with what word(s)?
    bacterium or prokaryotic cell
  180. Where is the genome found in a prokaryotic cell?
    One supercoiled double-stranded DNA chromosome is found in the cytoplasm, in a region called the nucleoid
  181. A difference between transcription in bacteria and transcription in eukaryotes pertains to the cellular site of transcription. Describe the difference.
    In the bacterium, transcription occurs in the cytoplasm because this is where the DNA template is found. In eukaryotes, transcription occurs in the nucleus (note that the synthesis of rRNA occurs, more specifically, within the nucleolus).
  182. A difference between transcription in bacteria and transcription in eukaryotes pertains to the multiple types of RNA polymerase. Describe this difference.
    In the bacterium, a single form of RNA polymerase mediates the synthesis of all types of RNA-mRNA, rRNA, tRNA. Eukaryotes, on the other hand, show no fewer than three different RNA polymerases (RNA Polymerase I synthesizes rRNA, RNA Polymerase II synthesizes mRNA, and RNA Polymerase III synthesizes tRNA)
  183. A difference between transcription in bacteria and transcription in eukaryotes pertains to the nature and complexity of promoters. Describe this difference.
    In bacteria, promoters show considerable commonality ("consensus sequences" at -10 and -35 positions upstream of start site). In eukaryotic cells, promoters are highly varied, longer, and more complex than those of bacteria.
  184. A difference between transcription in bacteria and transcription in eukaryotes pertains to transcription factors. Describe the difference.
    In bacterial transcription: the binding of RNA polymerase to the DNA promoter sites is a relatively simple affair, mediated by the sigma factor, which detaches from the RNA polymerase at the end of initiation. In eukaryotic cells, the binding of RNA polymerase to a promoter site is preceded by interactions among and between the DNA promoter site and several transcription factors (proteins)
  185. Which of the following is true of eukaryotic but not prokaryotic transcription?
    A. Promoters may be located upstream or downstream from the start site.
    B. The process is mediated by a single form of RNA polymerase.
    C. Enzyme binding to the promoter site is mediated by the sigma factor.
    D. The process occurs in the cytoplasm.
    A. Relative to the prokaryotic promoter sites, eukaryotic promoters are more complex and diverse in their nature and location; the promoter might be located upstream and/or downstream from the start site. In prokaryotes, the promoter is located upstream from the start site. The other choices make statements that are true of prokaryotic transcription, but not eukaryotic transcription.
    (this multiple choice question has been scrambled)
  186. The 5' cap is:
    A. positioned after the mRNA molecule leaves the nucleus
    B. composed of adenine residues located at the 3' end of eukaryotic RNA.
    C. found in the hairpin loop of prokaryotic RNA.
    D. a methylated guanine unit found in eukaryotic RNA.
    D. Addition of the 5' cap, a methylated guanine, is part of RNA processing in eukaryotes and occurs before the transcript leaves the nucleus. The choice that states the 5' cap is composed of adenine residues located at the 3' end of eukaryotic RNA describes a pony A tail. The answer that reads "found in the hairpin loop of prokaryotic RNA" refers to prokaryotic RNA, which often features the hairpin loop.
    (this multiple choice question has been scrambled)
  187. An intron is NOT normally:
    A. present in the primary transcript of eukaryotic transcription.
    B. part of a functional mRNA molecule.
    C. composed of purine and pyrimidine residues.
    D. excised from eukaryotic mRNA within the cellular nucleus.
    B. Before leaving the nucleus to enter the cytosol, eukaryotic primary transcripts undergo processing, including splicing out the introns and joining exons. Introns do not normally form a part of a functional mRNA molecule, but are present in the eukaryotic primary transcript. Like all components of the primary transcript, they are composed of nucleotide residues.
    (this multiple choice question has been scrambled)
  188. The first part of protein synthesis is transcription. The second part is translation: using the ribosome (including rRNA), tRNAs coupled to amino acids, and the mRNA to make a peptide chain. Give the general translation process.
    • 1. the ribosome recognizes some protein of the mRNA molecule and binds it;
    • 2. the ribosome reads the mRNA molecule, three nucleotides at a time (these three nucleotides are called a codon);
    • 3. when read by the ribosome, each codon on the mRNA orders that some particular amino acid be brought to the ribosome;
    • 4. molecules of tRNA within the cytosol bring amino acids to the ribosome, as instructed by mRNA; and
    • 5. amino acids brought to the ribosome, one by one, in a sequence ordered by the mRNA molecule, form peptide bonds to form a polypeptide.
  189. A prokaryotic ribosome embodies two subunits, a large one and a small one. What are these subunits called?
    50S and 30S where the S denotes the sedimentation rate and is a complex of rRNA, enzymes, and structural protein.
  190. The ribosome also features three tRNA binding sites. What are these sites called?
    A site (or aminoacyl-tRNA site), the P site (or peptidyl-tRNA site), and the E site (or exit-tRNA site).
  191. tRNA, or transfer RNA, is a single stranded molecule of RNA where regions that are complementary fold into a cloverleaf structure. tRNAs have two functional sites. Name those sites.
    The anticodon and the amino acid acceptor site.
  192. How many anticodons are there?
    64, there are four nucleotide options for each site (A, C, G, or U) and it is a sequence of three nucleotides, so 4x4x4=64
  193. How many amino acids are there?
    20 amino acids, so there might be more than one tRNA molecule specific to a given amino acid (the anticodones (3')-CGG-(5'), (3')-CGA-(5') and other anticodones will code for alanine and only alanine)
  194. On what basis does tRNA recognize the amino acid to which it is specific?
    For each amino acid, there exists (at least) one enzyme called an aminoacyl-tRNA sythetase.
  195. What is amino acid activation?
    • It is the binding of an amino acid to its tRNA to produce the corresponding aminoacyl-tRNA and is an endergonic (meaning ΔG is positive) reaction.
    • Amino Acid + ATP + tRNA ----->
    •      ------>Aminoacyl-tRNA + AMP + PPi
  196. Translation proceeds according to three phases. List them.
    • 1. an initiation phase
    • 2. an elongation phase
    • 3. a termination phase
  197. Among the following, which represents the earliest even associate with the initiation phase of translation in prokaryotes?
    A. Formation of a 70S ribosome
    B. Joining of the large ribosomal subunit to a molecule of mRNA
    C. Binding of N-formyl-methionyl tRNA to the start codon
    D. Binding of N-formyl-methionyl tRNA to the 50S subunit
    • C. In summary, the steps of translation initiation are:
    • 1. The 30S subunit binds the 5' end of the mRNA transcript.
    • 2. The UAC antocodon of fMET-tRNAMet recognizes and binds the AUG start codon on a molecule of mRNA
    • 3. The large ribosomal subunit joins the initiation complex to form the 70S ribosome.
  198. During the elongation phase, the ribosome reads the mRNA codons, tRNA molecules bearing appropriate anticodons bring amino acids to the ribosome, and peptide bonds form between the adjacent amino acids to form a polypeptide. The amino acid sequence of the polypeptide is dictated by the mRNA codons. In more detailed terms, give the series of events involved in elongation.
    • 1. a mRNA codon is exposed at the A site of the ribosome.
    • 2. An aminoacyl-tRNA, whose anticodon is complementary to the codon, arrives at the A site and forms hydrogen bonds with the codon. This step requires the hydrolysis of one phosphate from GTP.
    • 3. The enzyme peptidyl transferase transfers the amino acid in the P site from its tRNA carrier to the amino terminus of the aminoacyl-tRNA in the A site. A peptide bond is formed between the two amino acids. The bond between the amino acid and the tRNA in the P site is broken.
    • 4. The ribosome moves, or translocates, a distance of three nucleotides along the mRNA molecule in the 5' to 3' direction. Translocation moves the growing polypeptide anchored to a tRNA molecule to the P site of the ribosome, the old tRNA to the E site and exposes the next mRNA codon at the A site. This step requires the hydrolysis of one GTP.
  199. On a molecule of tRNA, the anticodon represents the means by which:
    A. the small and large ribosomal units recognize one another.
    B. an aminoacyl tRNA recognizes an mRNA codon.
    C. a tRNA molecule recognizes the amino acid to which it is specific.
    D. an mRNA codon locates itself at the ribosome's A site.
    B. is correct.
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  200. During the process of translation, translocation serves directly to:
    A. promote the formation of aminoacyl-tRNA.
    B. supply energy for peptide bond formation.
    C. allow for recognition between a tRNA molecule and the amino acid to which it is specific.
    D. expose a new mRNA codon at the ribosomal A site.
    D. is correct.
    (this multiple choice question has been scrambled)
  201. What are the three stop codons of the termination phase?
    • UAG, UGA, UAA - stop codons that upon appearing at the ribosomal A site will end translation elongation
    • Memory tool: "U Are Gone, U Go Away, U Are Away"
  202. Summarize the energetics of translation.
    The 1st amino acid requires the hydrolysis of three high-energy bonds. Each amino acid after this requires the hydrolysis of four high-energy bonds. Termination requires no energy requirement. So, overall proteins cost 4n-1 energy bonds to make, where n is the number of amino acids in the peptide chain.
  203. Among the following, a "codon" is best described as:
    A. a series of three tRNA nucleotide units recognized by complementary mRNA nucleotide units.
    B. a DNA template from which an mRNA molecule is synthesized.
    C. a series of three mRNA nucleotide units recognized by complementary tRNA nucleotide units.
    D. a group of polymerase enzymes that catalyze the elongation of nucleic acids.
    C. A codon is a series of three nucleotide units that are located on an mRNA molecule and are recognized by complementary nucleotide units on a tRNA molecule. The word codon is also used to describe a series of three nucleotides that causes protein synthesis to stop when a protein molecule is fully formed. That codon is called a stop codon. "A series of three tRNA nucleotide units..." describes an antocodon.
    (this multiple choice question has been scrambled)
  204. No tRNA molecule contains the nucleotide:
    A. cytosine.
    B. guanine.
    C. thymine.
    D. adenine.
    C. is correct.
    (this multiple choice question has been scrambled)
  205. Which of the following happens in the A site of the ribosome during translation?
    A. mRNA codons are exposed and joined by complementary tRNA molecules.
    B. N-formylmethionyl tRNA binds to the ribosome to create an initiation complex.
    C. DNA strands code for the synthesis of mRNA molecules.
    D. peptide bonds are broken and amino acids separate.
    A. During initiation, the ribosome assembles so that the fMet-tRNA is in the P site, not the A site. "DNA strands code for synthesis of mRNA molecules" describes transcription. While, "peptide bonds are broke and amino acids separate" describes peptide hydrolysis and is the opposite of protein synthesis.
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  206. An important difference between translation in prokaryotes and translation in eukaryotes pertains to ribosomes. Describe this difference.
    • Bacterial ribosomes comprise 30S and 50S subunits. Together, they make a 70S ribosome.
    • The eukaryotic ribosome comprises a 40S and 60S subunit which make an 80S ribosome. Eukaryotic ribosomes are synthesized in the nucleolus, which is also the site of rRNA synthesis.
    • Because prokaryotic ribosomes are different from eukaryotic ribosomes, many antibiotic drugs have been developed that target the prokaryotic ribosome.
  207. An important difference between translation in prokaryotes and translation in eukaryotes pertains to the source of mRNA. Describe this difference.
    Prokaryotes have no nucleus, and therefore no nuclear membrane. Transcription (mRNA synthesis) and translation (peptide synthesis) both occur in the cytoplasm. Eukaryotic transcription occurs in the coleus, and after processing, the mRNA must move through nuclear pores from the nucleus to the cytoplasm. All the translational machinery in a eukaryotic cell is housed in the cytoplasm.
  208. An important difference between translation in prokaryotes and translation in eukaryotes pertains to the structure of the 5' untranslated region (or 5'UTR). Describe this difference.
    Similar to the promoter used to initiate transcription, the 5'UTR can contain consensus sequences that are conserve between organisms and between genes. In both, the 5'UTR functions generally in assembly of the translation initiation complex. Different sequences are found in prokaryotes from eukaryotes and at different locations upstream of the start codon.
  209. An important difference between translation in prokaryotes and translation in eukaryotes pertains to the first amino acid. Describe this difference.
    In prokaryotes, N-formylmethionyl tRNA (or fMet-tRNA) is the first amino acid brought to the ribosome. In eukaryotes, the first amino acid is methionine itself, not N-formylmethionine. Note that methionine can be found within peptide chains as well; just because it is the first amino acid in proteins doesn't mean that is the only place it is found.
  210. An important difference between translation in prokaryotes and translation in eukaryotes pertains to timing. Describe this difference.
    • In prokaryotes, mRNA is made 5' to 3' via transcription. Once the 5' end of the transcript has been made by RNA polymerase, it can start to undergo translation. In prokaryotes, translation and transcription occur simultaneously; RNA polymerase can be building the 3' end of the mRNA as ribosomes are already reading the 5' end of the mRNA.
    • In eukaryotes, such synchrony is impossible because the two processes occur in different cellular compartments. Transcription takes place in the nucleus and translation in the cytoplasm. Also, mRNA processing must take place between transcription and translation in eukaryotes.
  211. Which of the following statements is true of prokaryotic but not eukaryotic translation?
    A. The process occurs in cytosol.
    B. The process is mediated by tRNA.
    C. The initiation phase begins with the binding of the small ribosomal subunit to the mRNA.
    D. The process occurs simultaneously with transcription.
    D. is correct.
    (this multiple choice question has been scrambled)
  212. A codon is a nucleotide sequence situated on a molecule of:
    A. rRNA
    B. DNA
    C. mRNA
    D. tRNA
    C. is correct.
    (this multiple choice question has been scrambled)
  213. The genetic code allows for the possibility that:
    A. some anticodons correspond to no codons.
    B. some amino acids do not correspond to codons.
    C. one codon is specific to more than one amino acid.
    D. more than one codon is specific to a single amino acid.
    D. is correct.
    (this multiple choice question has been scrambled)
  214. What does the term diploidy mean?
    Diploidy is the state in which every chromosome of a cell has a homologue. The diploid state is also designated 2N.
  215. How many chromosomes are contained in all human cells (other than the germ [i.e. sperm and ova]cells)?
    In the human, all cells other than the germ cells contain forty-six chromosomes, or twenty three homologous pairs.
  216. What does the term "haploid" mean?
    If one chromosome were removed from each of the twenty-three pairs in a diploid human cell, the cell would be left with twenty-three chromosomes in total. Each of the twenty-three chromosomes would lack a homologous counterpart, and the cell would be termed "haploid." For any organism the number of chromosomes in a haploid cell is one half the number of chromosomes in a diploid cell. The haploid condition is designated "1N."
  217. If a cell is diploid, then
    A. its nucleus contains single-stranded DNA.
    B. each of its chromosomes has a homologous counterpart.
    C. it contains two nuclei.
    D. if has one half the DNA content associated with a chromosome in the haploid state.
    B. is correct.
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  218. If for a given organism, the diploid number is 24, the haploid number is:
    A. 18.
    B. 9.
    C. 48.
    D. 12.
    D. is correct.
    (this multiple choice question has been scrambled)
  219. Once the zygote is formed, it enters into a series of rapid cell divisions. What are these divisions called? What type of division is occurring?
    Cleavage; mitotic division that doubles the cell count.
  220. Once the zygote approximately thirty-two cells, it becomes what is called a __________?
  221. What is the term used to describe what develops once the morula takes the shape of a hollow ball?
    A blastula (the blastocoel is its fluid-filled center)
  222. The hollow blastula will invaginate during what and what will it form? What does this invagination mark?
    During gastrulation to form the gastrula. It marks the beginning of mophogenesis, or "the genesis of form"
  223. After a period of cleavage, what is the developing organism first called?
    A. Morula
    B. Gastrula
    C. Zygote
    D. Gamete
    A. Cleavage is a series of rapid mitotic divisions that begin after fertilization of the ovum by a sperm cell.
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  224. The outermost germ cell layer is the:
    A. mesoderm.
    B. ectoderm.
    C. endoderm.
    D. epiderm.
    B. Through morphogenesis, the invaginated gastrula generates three distinct germ cell layers: the outermost is the ectoderm. The middle layer is the mesoderm, and the innermost layer is called the endoderm.
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  225. Ectoderm, endoderm, and mesoderm develop as a result of:
    A. programming within the genome.
    B. maternal intervention.
    C. random orientation.
    D. sex-linked determination.
    A. The formation of the three germ cell layers is genetically coded.
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  226. What occurs once gastrulation is complete and the three germ cell layers have been established?
    Neurulation occurs. A portion of the mesoderm forms a tubelike structure called the notochord. The notochord induces a thickening of the ectoderm directly above it. The thickened ectoderm forms the neural plate. Invagination causes it to assume a tubular shape and form the neural tube, a precursor to the brain, the spinal cord, and certain components of the eye, including the retina and optic nerve.
  227. Neurulation occurs just after:
    A. fertilization.
    B. morulation
    C. morphogenesis
    D. gastrulation
    D. Neurulation, the formation of the neural tube, occurs just after gastrulation. Morphogenesis is not a formal stage in development. It's part of gastrulation.
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  228. The invigination of the neural plate directly produces:
    A. the brain.
    B. the neural tube.
    C. the spinal column.
    D. the notochord.
    B. Neurulation involves formation of the notochord. This causes the development of the neural plate, which upon invagination, becomes the neural tube. The neural tube ultimately gives rise to the brain and spinal cord.
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  229. Trace the development of an embryo from zygote through neurula.
    The zygote undergoes cleavage to become first a morula (a cluster of 32 cells), then a blastula (a fluid-filled ball of hundreds of cells), then a gastrula (formed through invagination of the blastula), and then a neurula, at which stage the neural tube is formed through invagination of the neural plate.
  230. The process whereby development of one region of tissue is influenced by the tissues that surround it (like neurulation) is called what?
    Induction - In neurulation, the notochord releases chemical factors, called inducers, which activate certain genes in the ectodermal tissue. The products of the activated genes cause the tissue to undergo the process of neurulation.
  231. The process whereby a cell becomes more specialized (like the cells of the gastrula) is called what?
    Differentiation - the cells of the gastrula become differentiated when the three germ layers are formed. It is thereafter possible to distinguish a mesodermal cell from an ectodermal cell, for example.
  232. The process whereby the number of possible tissue types a cell could conceivable become is progressively limited is called what?
    Determination - Once it is possible to determine the mesodermal cell from an ectodermal cell, for example, it is no longer possible for it to become an ectodermal cell, at least under normal conditions. A mesodermal cell is now determined to become part of an organ that develops from the mesoderm.
  233. Induction may result in all the following EXCEPT:
    A. cell proliferation.
    B. cell genome modification.
    C. cell movement.
    D. cellular differentiation.
    B. In a developing organism, induction refers to the influence that one set of cells has on another nearby set. This influence can produce cell movement or determine the development of a cell group, but it cannot alter the genome.
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  234. The lining of the digestive tract and the lungs as well as the liver and the pancreas are formed from which germ cell layer?
    All of these develop from the endoderm
  235. The epidermis, the eye, and the nervous system are formed from which germ cell layer?
    The ectoderm
  236. The connective tissue, the heart, blood cells (red and white, including those of the lymphatic system), the urogenital system as well as parts of many other internal organs are formed from which germ cell layer?
    The mesoderm
  237. All of the following structures arise from the ectoderm EXCEPT:
    A. the nervous system.
    B. the outer layer of the skin.
    C. the excretory system.
    D. the structures of the eye.
    C. The outer layer of the skin, the nervous system, and the structures of the eye derive from ectoderm. The excretory system derives from mesoderm.
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  238. The retina develops from the same germ cell layer as does the:
    A. trachea.
    B. heart.
    C. brain.
    D. pancreas.
    C. The eye, the epidermis, and all the structures of the central nervous system develop from ectoderm as does the retina, being part of the eye, and the brain.
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  239. Which of the following structures derives from the same germ cell layer as the heart?
    A. Retina
    B. Bone
    C. Spinal cord
    D. Liver
    B. The heart derives from the mesoderm as do all structures other than (a)eye, epidermis, and nervous tissues (which develop from ectoderm) and (b) the inner linings of digestive organs and the respiratory tract, as well as the accessory organs to the digestive system (all of which derive from the endoderm). Heart and bone (among many other tissues and organs) derive from mesoderm.
    (this multiple choice question has been scrambled)
  240. Which of the following does NOT derive from the mesoderm?
    A. Muscles and associated connective tissues
    B. Arteries and arterioles
    C. Veins, venules, and capillaries
    D. Inner linings of the lungs
    D. The structures named in all three other choices derive from the mesoderm. All tissues and organs derive from the mesoderm except (a) the ectodermal structures: epidermis, eye, and nervous tissue, and (b) the endodermal structures: inner linings of the digestive tract and the respiratory tract, and the accessory digestive organs.
    (this multiple choice question has been scrambled)
  241. Why are viruses considered to be non-living?
    • 1. They do not grow by increasing in size.
    • 2. They can not carry out independent metabolism.
    • 3. They do not respond to external stimuli.
    • 4. They have no cellular structure.
  242. What is the genetic material for viruses?
    It may be DNA or RNA but never both.
  243. Put the following in order of size (starting with the smallest):
    Bacteria, Viruses, Eukaryotic cells
    Viruses, Bacteria (Prokaryotic cells), Eukaryotic cells
  244. What is a virus called that infects a bacteria?
    Bacteriophage or phage
  245. Describe the life cycle of the virus.
    • A virus attaches to a specific receptor on a cell.
    • Some viruses may now enter the cell; others will simply inject their nucleic acid.
    • Either way, viral molecules induce the metabolic machinery of the host cell to produce more viruses.
    • The new viral particles may now exit the cell by lysing (bursting). The preceding is deemed lytic or virulent.
    • Some viruses lie latent for long periods of time without lysing the host cell. These are called lysogenic or temperate viruses.
  246. How are metabolic processes carried out in bacteria?
    Since bacteria do not have a mitochondria, Golgi apparatus, lysosomes, nor endoplasmic reticulum, metabolic processes can be carried out in the cytoplasm or associated with bacterial membranes.
  247. Which of the following are NOT found in bacteria?
    A. Cell wall
    B. Plasma membrane
    C. Ribosomes
    D. Lysosomes
    D. Bacteria have ribosomes (smaller than eukaryotes). Their cell wall, made of peptidoglycans, helps to prevent the hypertonic bacterium from bursting. Some bacteria have a slimy polysaccharide mucoid-like capsule on the outer surface for protection.
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  248. Bacteria are partially identified by their shapes. Describe these shapes.
    • Cocci: spherical or sometimes elliptical
    • Bacilli: rod-shaped or cylindrical
    • Spirilli: helical or spiral
  249. Bacilli are:
    A. fungi with a spiral shape.
    B. bacteria with a rod shape.
    C. bacteria with a round or ovoid shape.
    D. bacteria with a spiral shape.
    B. Bacilli are rod-shape bacteria
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  250. Cocci are:
    A. bacteria with a spiral shape.
    B. bacteria with a rod shape.
    C. fungi with a spiral shape.
    D. bacteria with a round or ovoid shape.
    D. Cocci are bacteria with a round or ovoid shape.
    (this multiple choice question has been scrambled)
  251. Spirilla are:
    A. bacteria with a rod shape.
    B. fungi with a spiral shape.
    C. bacteria with a round or ovoid shape.
    D. bacteria with a spiral shape.
    D. Spirilla are spiral-shape bacteria.
    (this multiple choice question has been scrambled)
  252. Bacteria are partially identified by whether or not their cell wall reacts to a special dye. What is this called?
    Gram-stain: gram-positive if the stain is retained and gram-negative if not
  253. Most bacteria engage in a form of asexual reproduction. What is this called?
    Binary fission
  254. What is binary fission and how often can a bacterium undergo it?
    • Two identical DNA molecules migrate to opposite ends of a cell as a transverse wall forms, dividing the cell in two. The cells can now separate and enlarge to the original size.
    • Under ideal conditions, a bacterium can undergo fission every 10-20 minutes producing over 1030 progeny in a day and a half.
  255. How can the doubling time of bacterial populations be calculated?
    • b=B*2n where:
    • b is the number of bacteria at the end of the time interval
    • B is the number of bacteria at the beginning of the time interval
    • n is the number of generations
    • Thus if starting with 2 bacteria and follow for 3 generations then:
    • b=B*2n=2*23=2*8=16
    • note: bacterial doubling time is a relatively popular question type
  256. What are the three forms of genetic recombination (the acquiring of a different genome from that of its parents) that occur with bacteria?
    • transduction
    • transformation
    • conjucation
  257. What is bacterial transduction?
    Phages act as a vector transferring DNA between bacteria
  258. What is bacterial transformation?
    Bacteria incorporate free DNA from its immediate environment (i.e. from a dead cell which has released its DNA).
  259. What is bacterial conjugation?
    Part of the DNA strand may be passed from one mating type to another through a hollow tube (i.e. a pilus) while the two cells are in contact.
  260. Which of the following recombinant processes is dependent on the F factor plasmid?
    A. Crossing over
    B. Binary fission
    C. Conjugation
    D. Transduction
    C. Conjugation involves the direct transfer of genetic material from one bacterium to another. The transfer is mediated by a plasmid called the F factor.
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  261. Which of the following recombinant processes is carried out by a virus?
    A. Binary fission
    B. Transformation
    C. Conjugation
    D. Transduction
    D. Transduction involves the transfer of genetic material from one bacterium to another, with a virus acting as the carrier.
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  262. Which of the following does NOT constitute a recombinant process among bacteria?
    A. Conjugation
    B. Binary fission
    C. Transformation
    D. Transduction
    B. The three recombinant processes observed among bacteria are transduction, conjugation, and transformation.
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  263. Which of the following represents the incorporation of genetic material into a bacterial genome that is not necessarily from a bacterium?
    A. Translocation
    B. Conjugation
    C. Transformation
    D. Binary fission
    C. Transformation is the recombinant process in which a bacterium acquires genetic material that is not necessarily from a bacterium. The cell from which the material derives might, indeed, be prokaryotic or eukaryotic.
    (this multiple choice question has been scrambled)
  264. What is a heterotrophic bacterium?
    A bacterium that cannot synthesize its own food and must depend on other organisms for it.
  265. What are heterotrophic bacteria that obtain their food from dead organic matter called?
    Saprophytic: most heterotrophic bacteria are saprophytic
  266. What are autotrophic bacteria?
    Bacteria that can synthesize organic compounds from simple inorganic substances.
  267. What are photosynthetic bacteria?
    Autotrophic bacteria that produce carbohydrate and release oxygen.
  268. What are chemoautotrophic bacteria?
    Autotrophic bacteria that obtain energy via chemical reactions including the oxidation of iron, sulfur, nitrogen, or hydrogen gas.
  269. Bacteria can be either aerobic or anaerobic. Describe each term.
    • Aerobic: refers to metabolism in the presence of oxygen
    • Anaerobic: refers to metabolism in the absence of oxygen (i.e. fermentation)
  270. What type of anaerobe would die in the presence of oxygen?
    An obligate anaerobe would die in the presence of oxygen while a facultative anaerobe would survive.
  271. What type of organisms are fungi?
    They are eukaryotic (=true nucleus) organisms which absorb their food through their chitinous cell walls.
  272. Are fungi unicellular, filamentous, or both?
    They may be either unicellular (i.e. yeast) or filamentous (i.s. mushrooms, molds) with individual filaments called hyphae which collectively form a mycelium.
  273. How do fungi reproduce asexually?
    Spores (i.e. conidia) can be produced and then liberate from outside of a sporangium; or, as in yeast, a simple asexual budding process may be used.
  274. How may fungi be sexually reproduced?
    Sexual reproduction can involve the fusion of opposite mating types to produce asci (singular: ascus), basidia (singular: basidium), or zygotes. All of the three preceding diploid structures must undergo meiosis to produce haploid spores.
  275. True or false: All eukaryotes lack a cell wall.
    False. Animal cells lack a cell wall but fungi have cell walls.
  276. All viruses contain:
    A. lysosomes.
    B. antibodies.
    C. ribosomes.
    D. nucleic acid.
    D. All viruses contain genetic material (either DNA or RNA). They do not have organelles and must rely on the invaded body to provide the proteins.
    (this multiple choice question has been scrambled)
  277. Which of the following typically have a plasma membrane but no nuclear membrane?
    A. Viruses other than bacteriophages
    B. Bacteria
    C. Fungi
    D. Bacteriophages
    B. Viruses lack any type of membrane. They are surrounded by a protein coat and fungi are eukaryotes, meaning they have a nucleus.
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  278. The bacterium E. coli is normally killed by low concentrations of the antibiotic streptomycin. In a standard E. coli population, about 1 in 106 cells (0.0001%) are mutant that are resistant to streptomycin; that is, they can grow and divide in the presence of the antibiotic. Suppose that a rapidly growing population of E. coli is exposed to low streptomycin. What percentage of the cells will be resistant to streptomycin after 20 generations in the presence of the antibiotic?
    A) None of the cells
    B. About 0.0001 %
    C. About 20%
    D About 100%
    D. Since the antibiotic will kill all of those not resistant, even after just 2 generations, the answer would be about 100%.
  279. Most viruses are very host-specific because:
    A. the attachment to the hose involves the host's cell surface receptors.
    B. a virus has no cellular organelles.
    C. the viral capsid is composed of protein.
    D. viral nucleic acid might be DNA or RNA, depending on the virus.
    A. To state that a virus is host-specific is to state that any one virus will infect only a limited number of host cell types. Whether or not the virus will infect a given host is determined by the host's cell membrane receptors. If a given host has the receptors that will allow a given virus to attach, then viral infection by that virus is possible. Host cell receptors, therefore, create the specificity.
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  280. Which of the following precedes the replication of the viral nucleic acid?
    A. Assembly of viral progeny
    B. Replication of capsid protein
    C. Host cell lysis
    D. Attachment of the host cell receptors
    D. The question requires that the sequence associated with viral reproduction be understood: attachment, delivery of genome, replication of nucleic acid and capsid protein, assembly of new viruses, and lysis of the host.
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  281. Which of the following would be the most unlikely to occur after a virus has reproduced and its progeny have left the host cell?
    A. New infection by progeny virus of new host cells.
    B. Symptomatic disease in the organism to which the original host cell belonged.
    C. Death of the organism to which the original host cell belonged.
    D. Reproduction of the original host cell itself.
    D. In the final stage of viral reproduction, the host cell often undergoes lysis (bursting); it is destroyed. It cannot undergo reproduction thereafter.
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  282. Which of the following distinguishes a bacteriophage from other viruses?
    A. The presence of mitochondria
    B. The presence of RNA in the nucleic acid core
    C. The presence of a protein capsid
    D. The presence of a tail fiber
    D. The bacteriophage possesses the two structures that characterize the prototypical virus--a protein capsid and a nucleic acid core--and then a third, the tail fiber, which facilitates attachment to a bacterial cell. (Viruses that lack a tail fiber, nonetheless, attach themselves to their target hosts. They make direct attachment between the capsid and host cell membrane receptors.)
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  283. Which of the following does NOT posses a cell wall?
    A. A virus
    B. A fungal cell
    C. A plant cell
    D. A bacterium
    A. Bacteria, plant cells, and fungi do possess cell walls. Viruses do not; they are contained within a protein capsid. Indeed, the cell walls of bacteria promote the categorization of species according to Gram staining. A plant cell's cell wall is composed of cellulose, whose thickness and rigidity protect the cell against osmotic selling and injury. Fungi possess cell walls that are in most cases extremely rigid and are composed primarily of chitin.
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  284. Which among the following possesses such organelles as the endoplasmic reticulum, Golgi bodies, mitochondria, and a nuclear membrane?
    A. Fungi
    B. Viruses
    C. Prokaryotic cells
    D. Bacteria
    A. Fungi posses membrane-bound nuclei and other organelles ordinarily associated with eukaryotic cells. Prokaryotic cells possess neither a membrane-bound nucleus nor the organelles associated with eukaryotic cells. Bacteria are prokaryotic cells. Viruses do not possess any organelles.
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  285. Which of the following are NOT associated with asexual reproduction among fungi?
    A. Zygotes
    B. Hyphae
    C. Buds
    D. Spores
    A. With respect to fungi, zygotes form only in association with sexual reproduction. They are diploid and arise through the fusion of haploid gametes. The term spore refers to both sexual and asexual reproductive processes. In the asexual process, spores derive from hyphae.
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  286. Among the following processes, which one can give rise to progeny that are not genetically identical to the parents?
    A. Asexual spore formation
    B. Fission
    C. Budding
    D. Sexual reproduction
    D. is correct.
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  287. An organism that lacks a digestive system and obtains nutrients from other living organisms while harming the organism is:
    A. saprophytic.
    B. carnivorous.
    C. autotrophic.
    D. parasitic.
    D. If an organism cannot synthesize its own nutrients, it is a heterotroph. If it lacks a digestive system, it is not a herbivore, carnivore, or omnivore. It is either a parasite or a saprophyte. If it fees on the remains of deceased organisms, it is a saprophyte. If it feeds on living organisms and harms them in the process, it is a parasite.
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  288. An organism that captures its own energy is called:
    A. saprophytic.
    B. heterotrophic.
    C. autotrophic.
    D. omnivorous.
    C. If an organism synthesizes its own energy, it is autotrophic. The term heterotroph refers to those organisms that do not synthesize their own energy, and the terms saprophytic and omnivorous are subcategories within the classification heterotroph.
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  289. Which of the following is characteristic of saprophytic organisms?
    A. They recycle biological substances.
    B. They harm other living organisms.
    C. They obtain nutrients from living organisms.
    D. They obtain energy through photosynthesis.
    A. Saprophytes are heterotrophs that (a) lack a digestive system and (b) absorb nutrients from the remains of dead organisms. Saprophytes often recycle a variety of substances that are useful to other organisms within their ecosystem.
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  290. Which of the following characterizes anaerobic respiration?
    A. It is dependent on the remains of other organisms.
    B. It is a respiratory process that cannot operate in the presence of oxygen.
    C. it is a respiratory process that can operate in the absence of oxygen.
    D. It is dependent on living organisms and harms them.
    C. Anaerobic respiration does not require oxygen, but oxygen does not, on the other hand, render it inoperative.
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  291. Which of the following classes of bacteria can survive in the presence or absence of oxygen?
    A. Aerobes
    B. Obligate anaerobes
    C. Saprophytes
    D. Facultative anaerobes
    D. is correct.
    (this multiple choice question has been scrambled)
  292. Nitrogen-fixing bacteria are classified as:
    A. parasites.
    B. saprophytes.
    C. heterotrophs.
    D. autotrophs.
    C. Nitrogen-fixing bacteria have a mutualistic relationship with root nodules of certain legumes. They are heterotrophs; they cannot synthesize their own food and must obtain their nutrients from other organisms. Since the relationship is mutualistic (they convert nitrogen into a form that can be used), they are not parasites. Autotrophs conduct photosynthesis or obtain their energy from inorganic chemical bonds. Nitrogen-fixing bacteria do not.
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  293. What can have a potent regulatory effect on protein synthesis (especially enzymes)?
  294. What are allosteric enzymes?
    • Proteins with two different configurations, each with different biological properties
    • Important regulators of transcription
  295. tRNA and mRNA differ in that:
    A. only tRNA is involved in polypeptide synthesis.
    B. only mRNA is found associated with ribosomes.
    C. only tRNA links to a specific amino acid.
    D. only mRNA contains uracil.
    C. Transfer RNA (tRNA has the exclusive role of recognizing mRNA codons with its own anticodon and transferring its attached specific amino acid to polypeptide chain.
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  296. What do the ends of each protein created during the translation process have?
    One end of the protein has an amino group (-NH2, which projects from the first amino acid), while the other end has a carboxylic acid group (-COOH, which projects from the last amino acid).
  297. What are proteins made on free ribosomes in the cytoplasm use for?
    Intracellular purposes (i.e. enzymes for glycolysis, etc.)
  298. What are proteins made on rER ribosomes used for?
    Those proteins are usually modified by both rER and the Golgi apparatus en route to the plasma membrane or exocytosis (i.e. antibodies, intestinal enzymes, etc.)
  299. What is catabolism?
    It is one of two main categories of metabolism and is the breakdown of macromolecules (larger molecules) such as glycogen to micromolecules (smaller molecules) such as glucose
  300. What is anabolism?
    It is one of two main categories of metabolism and is the building up of macromolecules such as protein using micromolecules such as amino acids.
  301. Catabolic and anabolic reactions would involve massive amounts of energy if they were to occur in vitro (outside the cell). What substance allows these reactions to be carried out within a lower temperature range?
  302. What is an enzyme?
    It is a protein catalyst. It is a substance that alters the rate of a chemical reaction without itself being permanently change into another compound. It accelerates a reaction by decreasing the free energy of activation (see Chemistry).
  303. A catalyst:
    A. increases activation energy.
    B. promotes exothermicity.
    C. decreases activation energy.
    D. decreases free energy.
    C. All catalysts (including enzymes) serve to reduce activation energy. They do not promotes exothermicity or endothermicity, and they have no effect on free energy.
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  304. After an enzyme has catalyzed a reaction several times, the quantity of the enzyme within that cell will have:
    A. remained unchanged.
    B. increased.
    C. increased, decreased, or remained unchanged, depending on the reaction.
    D. decreased.
    A. Enzyme concentration undergoes no net change during the course of the reaction it catalyzes. Enzymes are "recycled"; an enzyme molecule will catalyze a reaction over and over again.
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  305. Enzymes fall into two general categories. What are they?
    • (a) Simple proteins which contain only amino acids like digestive enzymes ribonuclease, trypsin and chymotrypsin.
    • (b) Complex proteins which contain amino acids and a non-amino acid cofactor. Thus the complete enzyme is called a holoenzyme and is made up of a protein portion (apoenzyme) and a cofactor.
    •          Holoenzyme = Apoenzyme + Cofactor
  306. What may serve as a cofactor for the holoenzyme?
    • A metal: For example, Zinc is a cofactor for the enzymes carbonic anhydrase and carboxypeptidase.
    • An organic molecule: Such as pyridoxal phosphate or biotin. Cofactors such as biotin, which are covalently linked to the enzyme are called prosthetic groups or ligands.
  307. In addition to their enormous catalytic power which accelerates reaction rates, what do enzymes exhibit in the types of reactions that each catalyzes as well as for the substrates upon which they act?
    Exquisite specificity
  308. How do enzymes have their exquisite specificity?
    • Their specificity is linked to the concept of an active site.
    • An active site is a cluster of amino acids within the tertiary (i.e. 3-dimensional) configuration of the enzyme where the actual catalytic events occurs.
    • The active site is often similar to a pocket or groove with properties (chemical or structural) that accommodate the intended substrate with high specificity.
  309. There is an increase in reaction velocity with an increase in the concentration of substrate. At increasingly higher substrate concentrations the increase in activity is progressively smaller. What can be inferred from this and what is the mechanism of this?
    • Enzymes exhibit saturation kinetics.
    • The mechanism that lies largely with feedback inhibition - when the product of the enzyme catalyzed reaction returns (feeds back) to prevent or inhibit further reactions between the enzyme and its substrate
  310. How are enzyme inhibitors classified?
    • Reversible: these generally interact non-covalently and virtually instantaneously with an enzyme.
    • Irreversible: these usually react covalently to render the enzyme inactive.
  311. All of the following are true of enzymes EXCEPT:
    A. they increase the equilibrium concentration of product.
    B. they are proteins.
    C. they lower the activation energy of a reaction.
    D. they increase the rate at which a reaction will take place.
    A. All other choices are true statements.
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  312. Among the following choices, which would most likely happen to an enzyme exposed to a temperature of 150°C?
    A. Excessive activity
    B. Desaturation
    C. Denaturation
    D. Saturation
    C. Every enzyme operates best within a relatively narrow range of temperature. The is the principal reason that changes in human body temperature threaten health. If body temperature exceeds the upper or lower limits of various enzymes, then death or severe cell injury may result. In particular, excessively high temperatures disrupt the enzymes molecule's three-dimensional structure. This process is called denaturation.
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  313. The saturation point of an enzyme is reached when:
    A. the enzyme experiences feedback inhibition.
    B. all available active sites on enzyme molecules are occupied by substrate molecules.
    C. an enzyme-substrate complex is formed from reactants and enzyme.
    D. the concentration of end products of the reaction exceeds the cell's need.
    B. The saturation point is that point at which the concentration of substrate is sufficiently high that all available enzyme molecules are in use; the active sites are saturated, and no additional substrate will increase the reaction rate.
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  314. If, during a particular enzymatic reaction, product concentration becomes excessively high, which of the following processes would most likely reduce enzymatic activity?
    A. Denaturation
    B. Competitive inhibition
    C. Feedback inhibition
    D. Saturation
    C. Feedback inhibition refers to a phenomenon in which the accumulation of product inhibits the activity of the enzyme. This mechanism prevents the cell from accumulating excess product.
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  315. How is the enzyme activity in the cell regulated?
    • Induction: enhancement of its synthesis
    • Repression: a decrease in its biosynthesis
    • Covalent modification: Phosphorylation of specific serine residues by protein kinases increases or decreases catalytic activity depending upon the enzyme. Proteolytic cleavage of proenzymes (e.g., chymotrypsinogen, trypsinogen, protease and clotting factors) converts an inactive form to an active form (e.g., chymotrypsin, trypsin, etc.)
    • Environment: especially pH and temperature (most enzymes exhibit optimal activity at a pH in the range of 6.5-7.5)
    • Non-covalent or allosteric mechanisms: Isocitrate dehydrogenase is an enzyme in the Kreb's Tricarboxylic Acid Cycle, which is activated by ADP, which is not a substrate or substrate analogue. It is postulated to bind a site distinct from the active site called the allosteric site.
    • Some enzymes fail to behave by simple saturation kinetics. In such cases, a phenomenon called positive co-operativity is explained in which binding of one substrate or ligand makes it easier for the second to bind.
  316. Biological species must transform energy into readily available sources in order to survive. What is the body's most important short term energy storage molecule?
    ATP: adenosine triphosphate
  317. How can ATP be produced?
    It can be produced by the breakdown or oxidation of protein, lipids (i.e. fat) or carbohydrates (esp. glucose).
  318. What are the long term and short term sources of energy for the body?
    • Medium term:
    • glycogen (broken down to glucose)
    • Long term:
    • fat (broken down to fatty acids)
    • protein - as a last resort (amino acids)
    •      fatty acids and amino acids can enter the Kreb's cycle
    • Short term:
    • ATP (1 GTP is approx. equal to 1 ATP)
  319. If the body is no longer ingesting sources of energy, what occurs?
    It can access its own stores: glucose is stored in the liver as glycogen, lipids are stored throughout the body as fat, and ultimately, muscle can be catabolized to release protein (esp. amino acids).
  320. What are the four key processes that can lead to the production of ATP?
    • Glycolysis
    • Kreb's Citric Acid Cycle
    • The electron transport chain (ETC)
    • Oxidative phosphorylation
  321. What is the Embden-Meyerhof glycolytic pathway?
    The initial steps in catabolism or lysis of D-glucose constitute the Embden-Meyerhof glycolytic pathway.
  322. Is the Embden-Meyerhof glycolytic pathway aerobic or anaerobic?
    It can occur in the absence of oxygen (anaerobic).
  323. Where are the enzymes for glycolysis present?
    In all human cells and are located in the cytosol
  324. Give the overall reaction of glycolysis.
    • Glucose + 2ADP + 2NAD++ 2Pi
    •      2Pyruvate + 2ATP + 2NADH + 2H+
    • ADP: adenosine diphosphate
    • NAD: nicotinamide adenine dinucleotide
    • Pi: inorganic phosphate
  325. What does the first step in glycolysis involve?
    the phosphorylation of glucose by ATP.
  326. What is the rate limiting step of glycolysis?
    The third step, where phosphofructokinase (PFK) catalyzes the second phosphorylation. It is an irreversible reaction. It produces fructose-1,6-disphosphate from fructose-6-phosphate.
  327. What occurs with pyruvate under aerobic and anaerobic conditions?
    • Aerobic: pyruvate is converted to Acetyl CoA which will enter the Kreb's Cycle followed by the oxidative phosphorylation producing a total or 38 ATP per molecule of glucose (i.e. 2 pyruvate)
    • Anaerobic: pyruvate is quickly reduced by NADH to lactic acid using the enzyme lactate dehydrogenase. A net of only 2 ATP is produced per molecule of glucose (this process is called fermentation)
  328. What do the kinases and phosphorylases add or subtract?
    They are enzymes that add or subtract phosphate groups.
  329. In simple terms, describe glycolysis.
    • It is the breaking apart of glucose.
    • Insulin helps to get glucose across the cell into the cytoplasm.
    • It wants to keep it in the cell, so it gets a big phosphate group.
    • It then changes to a fructose with a phosphate.
    • It then gets another phosphate group. By having TWO phosphate groups on a single molecule, the molecule becomes unstable and breaks apart because the two phosphate groups repel.
    • It goes through lysis to become 2 trioses (two phosphate trioses)
    • These transform to 2 pyruvate. It is the critical factor to determine whether things will proceed with or without oxygen.
    • (At this point 2 ATP has been produced - some energy is released - and get some reducing equivalents - 2 NADH + H which feed into the Electron Transport system to create more ATP)
    • If no oxygen (anaerobic, fermentation), mammals get lactic acid production.
    • If oxygen, then the pyruvate will enter the mitochondrian (the powerhouse of the cell) and produces 2 Acetyl CoA (Acetyl coenzyme A) that enters into the Kreb's cycle.
  330. During the first event of glycolysis, what prevents the glucose from leaking out of the cell?
    The first event in glycolysis is the phosphorylation of glucose. The negative charge prevents it from leaking out of the cell.
  331. What is it called when ATP is produced from a substrate like 1,3-diphosphoglycerate?
    substrate level phosphorylation
  332. Not only carbohydrates use the TCA for channeling their metabolic pathways. What else uses the TCA?
    Lipids and proteins also use the Tricarboxylic Acid Cycle for channeling their metabolic pathways. This is why TCA is often called the final common pathway of metabolism.
  333. Give key points to remember about the Tricarboxylic Acid Cycle (TCA) or Kreb's Cycle:
    1) glucose → 2 acetyl CoA → ?
    2) ? per turn is generated as a waste product
    3) one GTP (guanosine triphosphate) per turn is produced by ?
    4) reducing equivalents are hydrogens which are cared by ? three times per turn and ? once per turn; these reducing equivalents will eventually be oxidized to produce?
    5) the hydrogens (H) which are reducing equivalents are not ?
    • 1) glucose → 2 acetyl CoA → 2 turns around the TCA Cycle (Kreb's cycle)
    • 2) 2 CO2 per turn is generated as a waste product which will eventually be blown off in the lungs
    • 3) one GTP per turn is produced by substrate level phosphorylation; one GTP is equivalent to one ATP (GTP + ADP → GDP + ATP)
    • 4) reducing equivalents are hydrogens which are carried by NAD+ (→NADH + H+) three times (producing 3 ATP) per turn and FAD (→FADH2) once per turn (producing 2 ATP); these reducing equivalents will eventually be oxidized to produce ATP (oxidative phosphorylation) and eventually produce H2O as a waste product (the last step in ETC)
    • 5) the hydrogens (H) which are reducing equivalents are not protons (H+). Often the reducing equivalents are simply called electrons.
  334. To what does the term oxidative phosphorylation refer?
    To reactions associated with oxygen consumption and the phosphorylation of ADP to yield ATP
  335. Oxidative phosphorylation is associated with ________ __________ ____ which is found in the inner mitochondrial membrane of eukaryotes. (A similar process occurs within the plasma membrane of prokaryotes such as E.coli.)
    an Electron Transport Chain or Respiratory Chain
  336. What accounts for the reoxidation of reducing equivalents generated in the reactions of the Kreb's Cycle as well as in glycolysis?
    Oxidative phosphorylation
  337. 1 NADH produces how many ATP molecules while 1 FADH2 produces how many?

    What is the cost of getting two molecules of NADH generated in the cytoplasm to enter the mitochondrion?

    What is the net yield of ATP for eukaryotes?
    • 1 NADH produces 3 ATP molecules
    • 1 FADH2 produces 2 ATP molecules

    The cost is 2 ATP to get the two molecules of NADH generated in the cytoplasm to enter the mitochondrion

    The net yield for eukaryotes is 36 ATP
  338. What molecule receives the final hydrogens in the ETC?
    On oxygen to produce water.
  339. What are the waste products for aerobic respiration?
    CO2 and water
  340. How many turns of the citric acid cycle are required to account for net oxidation of one molecule of glucose to carbon dioxide and water?
    A. 1
    B. 4
    C. 2
    D. 0
    C. is correct.
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  341. In eukaryotic cells, cellular respiration occurs in the:
    A. ribosomes.
    B. ATP.
    C. mitochondria
    D. cytosol.
    C. is correct.
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  342. Which of the following metabolic processes predominates in rapidly contracting white muscle fibers?
    A. Kreb's Citric Acid Cycle
    B. Alcoholic fermentation
    C. Oxidative phosphorylation
    D. Glycolysis
    D. Glycolysis is much faster (though less efficient) than aerobic respiration. Note that fermentation in vertebrates produces lactate, no alcohol.
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  343. As re muscle fibers go from a resting state to a rapidly contracting state, which of the following occurs?
    A. Decreased rate of degradation of glucose
    B. Decreased rate of hydrolysis of ATP
    C. Decreased rate of production of carbon dioxide
    D. Increase rate of consumption of oxygen
    D. Aerobic respiration involves an increased use of energy (ATP) which requires more oxygen, more glucose, more hydrolysis of ATP and more CO2 is produced.
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  344. Suppose that the oxygen supply to continuously contracting red muscle fibers is abruptly cut off. Which of the following processes would occur in the muscles?
    A. Increased rate of synthesis of muscle glycogen
    B. Increased rate of production of carbon dioxide
    C. Increased rate of production of lactic acid
    D. Increased rate of production of ATP
    C. Conversion to anaerobic respiration means less efficiency, less ATP, increased lactic acid (fermentation), more need for glucose which means more breakdown of glycogen and reduced production of the waste products of aerobic respiration: CO2 and H2O
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  345. Cyanide inhibits specific oxidation-reduction reactions in the electron transport chain. Suppose a culture of bacteria capable of carrying out both anaerobic and aerobic metabolism is utilizing glucose in the presence of oxygen, and cyanide is added to the culture medium. What will happen to glucose metabolism and ATP production?
    A. Aerobic glucose metabolism will continue; ATP production will be uncoupled from the oxidation of NADH in the electron transport chain.
    B. Anaerobic glucose metabolism will continue; less ATP will be produced per glucose molecule metabolized.
    C. Aerobic glucose metabolism will continue; the same amount of ATP will be produced per glucose molecule metabolized.
    D. Anaerobic glucose metabolism will continue; the same amount of ATP will be produced per glucose molecule metabolized.
    B. The electron transport chain is part of aerobic metabolism and so inhibition of the ETC will block aerobic glucose metabolism while allowing anaerobic respiration to continue. Moreover, blocking of aerobic metabolism will produce only 2 ATP per glucose molecule rather than 36 ATP as normally occurs under aerobic conditions. Cyanide will shut down aerobic respiration forcing anaerobic fermentation which is less efficient.
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  346. In which order of priority are the human body's nutrient stores utilized for energy production during fasting and subsequent starvation?
    A. Fat, glycogen, protein
    B. Fat, protein, glycogen
    C. Glycogen, fat, protein
    D. Glycogen, protein, fat
    C. Glucose (from glycogen) is the first and most common source to produce ATP. Amino acids, which requires the breakdown or protein in muscle which would be fed into the Kreb's cycle, would only be used when all else fails.
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  347. All of the following changes would serve to adapt the muscles of marathon runners to the demands of prolonged muscular contraction EXCEPT an increase in the:
    A. dependence of muscle contraction upon glycolysis.
    B. levels of carbohydrate in muscle.
    C. density of red blood cells in the blood.
    D. density of mitochondria in muscle.
    A. A marathon runner must use energy efficiently. Glycolysis would be avoided since it is a very inefficient way to make ATP.
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  348. Which of the following does NOT accurately characterize glycolysis as it occurs in animal cells?
    A. it occurs in the cytoplasm, where the required enzymes and molecules are present.
    B. It is an anaerobic process that occurs in both aerobes and anaerobes.
    C. Two ATP molecules are required for initiation and four ATP molecules are ultimately produced.
    D. One molecule of glucose is converted to one molecule of pyruvate.
    D. Glycolysis is an anaerobic process and occurs in the cytoplasm of both aerobic and anaerobic organisms. Moreover, it requires, for its initiation, two molecules of ATP, and produces 4 ATP for a net yield of 2 ATP. The statement, "one molecule of glucose is converted to one molecule of pyruvate" is false because for each molecule of glucose that enters the glycolytic pathway, two molecules of pyruvic acid are produced.
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  349. Which of the following statements best characterizes glycolysis?
    A. It is an anaerobic process that produces a net yield of four ATP molecules.
    B. It is an aerobic process that yields ethyl alcohol.
    C. It is an anaerobic process that produces a net yield of two ATP molecules.
    D. It is an aerobic process that yields lactic acid.
    C. Glycolysis involves the degradation of a six-carbon molecule (glucose) into two three-carbon molecules (pyruvate). The process requires an input of two ATP molecules and produces four ATP molecules, for a net yield of two ATP molecules. Glycolysis occurs in the absence of oxygen.
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  350. Which of the following best characterizes fermentation?
    A. It is an aerobic process that yields lactic acid.
    B. It is an anaerobic process that produces four ATP molecules.
    C. It is an anaerobic process that produces no ATP.
    D. it is an aerobic process that yields ethyl alcohol.
    C. Under anaerobic conditions, fermentation follows glycolysis. Through fermentation, pyruvic acid is converted to either (a) lactic acid or (b) ethyl alcohol and carbon dioxide. Fermentation does not produce ATP.
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  351. Which of the following substances most likely causes the pain associated with muscle fatigue?
    A. Pyruvate
    B. Carbon dioxide
    C. Lactate
    D. Ethyl alcohol
    C. A rapidly exercising muscle may require more oxygen than is delivered to it. The result is that it experiences oxygen deprivation and cannot carry on the aerobic processes that would otherwise follow glycolysis. The pyruvate produced during glycolysis instead undergoes fermentation and is converted to lactate, which probably causes muscle fatigue.
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  352. Each turn of the Kreb's cycle oxidizes citric acid in a stepwise fashion and stores the liberated energy is what forms?
    • (a) 3 molecules of NADH
    • (b) 1 molecule of FADH2, and
    • (c) 1 molecule of GTP
    • Two molecules of CO2 are also produced.
  353. How many turns of the Kreb's cycle is generated by one molecule of glucose?
    • Two turns, producing:
    • (a) 4 molecules of CO2,
    • (b) 6 molecules of NADH,
    • (c) 2 molecules of FADH2, and
    • (d) 2 molecules of GTP
  354. Which of the following does NOT represent an energy-rich molecule that contributes, ultimately, to the energy housed within an ATP molecule?
    A. CO2
    B. NADH
    C. FADH2
    D. GTP
    A. Within the realm of biochemical systems, neither water nor carbon dioxide contains significant amounts of chemical energy
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  355. In the electron transport chain, oxygen serves to:
    A. mediate the movement of electrons from NADH and FADH2 to the cytochrome carrier molecules.
    B. generate CO2 from carbon derived from cytochrome carrier molecules.
    C. accept electrons donated by NADH and FADH2
    D. serve as the ultimate reducing agent for the storage of energy.
    C. The electron transport chain "passes electrons" from one oxidizing agent to the next, releasing energy with each pass. The ultimate oxidizing agent (electron acceptor) is oxygen, which when combined with electrons (and free-floating protons) forms water.
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  356. The electron transport chain serves to:
    A. move energy from GTP to ATP.
    B. move energy from glucose to NADH and FADH2.
    C. liberate energy through a series of oxidation-reduction reactions.
    D. oxidize water and carbon dioxide so that the energy they contain can be released for use by the cell.
    C. The electron transport chain is composed of a series of molecules that pass electrons from one another, the donor being oxidized and the recipient being reduced. Energy is liberated through this process.
    (this multiple choice question has been scrambled)
  357. The movement of hydrogen ions from the mitochondrial matrix to the intermembrane space serves to:
    A. provide the energy gradient necessary to initiate and perpetuate the sequential delivery of electrons from one cytochrome carrier to the next.
    B. promote the synthesis of enzymes necessary to generate ATP molecules from ADP and inorganic phosphate.
    C. establish and electrochemical gradient that promotes the passive transport of protons and a concomitant conversion of potential energy to chemical energy.
    D. provide an environment in which electrons may be accepted by oxygen and free-floating protons and thereby regenerate water molecules disrupted during the Krebs cycle.
    C. The electron transport chain uses some of the energy liberated through oxidation-reduction reactions to pump protons from the matrix into the intermembrane space. This gradient stores potential energy. The protons flow down their gradient, through ATP synthetase complexes, and back into the matrix. ATP synthetase converts the potential energy of the gradient into chemical energy when it catalyzes the synthesis of ATP from ADP and inorganic phosphate.
    (this multiple choice question has been scrambled)
  358. Oxidative phosphorylation occurs:
    A. on the nuclear membrane before electron transport.
    B. on the inner mitochondrial membrane contemporaneous with electron transport.
    C. in the cytoplasm after electron transport.
    D. in the mitochondrial cytoplasm before electron transport.
    B. The process of oxidative phosphorylation refers to the formation of ATP from ADP and inorganic phosphate. It is driven by the release of potential energy, which is stored in the electrochemical gradient created by the movement of hydrogen ions from the mitochondrial matrix into the intermembrane space. That movement of hydrogen ions is fueled by energy derived from electron transport. Oxidative phosphorylation is coupled with electron transport, and it occurs on the inner mitochondrial membrane through the action of ATP synthetase. The other choices inaccurately describe the site at which oxidative phosphorylation occurs and do not reflect the concept that electron transport and oxidative phosphorylation are coupled.
    (this multiple choice question has been scrambled)
  359. With regard to cellular respiration, which of the following statements are true?
    A. Electrons and hydrogen ions are passed along a chain of electron transport molecules in a process that requires the input of energy.
    B. Glycolysis requires two ATP molecules and produces two ATP molecules, yielding a net production of zero ATP molecules.
    C. The Krebs cycle produces three molecules of NADH for each molecule of glucose that is degraded.
    D. Carbon dioxide is formed during the Krebs cycle.
    D. During the Krebs cycle, two carbon dioxide molecules are released. The choice that states "glycolysis requires two ATP molecules....a net production of zero ATP molecules" is false because glycolysis offers a net yield of two ATP molecules, requiring two at initiation and generating four by completion. The statement about the Krebs cycle producing 3 molecules of NADH is similarly false. The Krebs cycle produces three molecules of NADH per molecule of acetyl CoA that enters the cycle. However, two molecules of acetyl CoA enter the cycle per molecule of glucose degraded (each arising from a molecule of pyruvate). The last choice is false because it describes electron transport as a process, with oxygen serving as the electron acceptor.
    (this multiple choice question has been scrambled)
  360. In comparison to anaerobic respiration, aerobic respiration yields:
    A. lesser quantities of ATP, because iron within the cytochrome carrier system competes for active sites on the ATP synthetase molecule.
    B. greater quantities of ATP, because the presence of oxygen, a strong oxidizing agent, facilitates greater oxidation of glucose molecule.
    C.  greater quantities of ATP, because aerobic processes avoid the accumulation of lactic acid.
    D. lesser quantities of ATP, because oxygen has such a strong affinity for electrons that is obstructs the electron transport system.
    B. Aerobic respiration makes more efficient use of the glucose molecule than anaerobic respiration. When glycolysis is complete, fermentation reoxidizes NADH, converting it to NAD+, a process that does not produce ATP. In aerobic respiration, however, NADH and FADH2 donate their electrons into the electron transport system, which converts some of the stored energy into a gradient that is used to produce more ATP. In order to do this, however, there must be a final electron acceptor, or else the electrons would accumulate. Oxygen fulfills this role.
    (this multiple choice question has been scrambled)
  361. Which of the following statements most likely represents the reason that oxidative phosphorylation occurs on the inner mitochondrial membrane?
    A. The membrane permits passive diffusion of protons.
    B. The membrane permits active transport of protons.
    C. ATP synthetase is located on the membrane.
    D. The enzymes that catalyze the glycolytic pathway are located on the membrane.
    C. ATP synthetase is located in the inner mitochondrial membrane. This could be inferred since such an enzyme is necessary to ATP synthesis. The other choices make inaccurate statements.
    (this multiple choice question has been scrambled)
  362. The phrenic nerve carries its signal:
    A. from the lungs to the cerebral cortex.
    B. from the diaphragm to the lungs.
    C. from the cerebral cortex tot he lungs.
    D.  from the medulla oblongata to the diaphragm.
    D. The signal that initiates inspiration originates in the respiratory center of the medulla oblongata and is sent to the diaphragm via the phrenic nerve.
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  363. Expansion of the lungs occurs in response to:
    A. relaxation of the diaphragm.
    B. negative pressure within the esophagus.
    C. negative pressure between the diaphragm and the lungs.
    D. elimination of elasticity within the lungs.
    C. Contraction of the diaphragm increases the space between the lungs and the diaphragm, thus creating a negative pressure in the pleural cavity around the lungs. This negative pressure causes the lungs to expand and consequently produces a negative pressure within the lungs themselves. That negative pressure is equilibrated by air flowing inward through the respiratory tract.
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  364. The cartilaginous rings that surround the trachea and bronchi serve to:
    A. keep the airway open.
    B. create the negative pressure generated by the contraction of the diaphragm.
    C. maintain the movement of cilia within the airway.
    D. facilitate the transmission of respiratory signals from the medulla oblongata.
    A. The horseshoe-shaped cartilaginous rings that surround the trachea and bronchi hold the airway open (patent). You  might think of it as a vacuum cleaner hose, which maintains its patency through the rigidity of stiff rings that support its otherwise collapsible walls.
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  365. Outgoing air from the body follows which one of the following pathways.
    A. Trachea, bronchi, bronchioles, alveoli
    B. Alveoli, bronchioles, bronchi, trachea
    C. Bronchioles, bronchi, trachea, alveoli
    D. Bronchi, bronchioles, trachea, alveoli
    B. In coming air travels through the trachea, the bronchi, the bronchioles, and the alveoli; outgoing air follows the reverse pathway out of the body.
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  366. Inspiration and expiration are necessary for the maintenance of gas exchange between an alveolus and a pulmonary capillary because:
    A. gas exchange is dependent on the equality of gas concentrations across the alveolar membrane.
    B. the concentration gradients would disappear without them.
    C. the phrenic nerve sends signals directly to the alveoli.
    D. body cells would cease to metabolize in their absence.
    B. With respect to alveolar air, gas exchange across the alveolar membrane tends to increase the carbon dioxide concentration and decrease the oxygen concentration. In order to maintain the concentration gradient that drives the gas exchange, carbon dioxide must be expelled from the lungs and oxygen must be drawn inward. Expiration serves the first purpose, and inspiration, the second.
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  367. A decreased concentration of surfactant leads to:
    A. an inability of the phrenic nerve to transmit signals to the diaphragm.
    B. a decrease in surface area for alveolar gas exchange.
    C. a decrease in pulmonary elastic recoil.
    D. an inability to inspire air.
    B. If alveoli collapse, then the surface area for gas exchange decreases. Alveoli are more likely to collapse when surfactant is not present in sufficient quantities.
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  368. Vigorous exercise would tend to:
    A. increase blood pH.
    B. decrease blood carbon dioxide concentration.
    C. increase blood oxygen concentration.
    D. reduce blood pH.
    D. Increased metabolic activity of any tissue or organ produces increase quantities of carbon dioxide, which is carried away from the tissues by the blood. The gas combines with water to form carbonic acid, which then dissociates into protons and bicarbonate ions. An increase in proton concentration is the same as a decrease in pH.
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  369. Decreased blood pH will:
    A. increase respiratory rate, and it accompanies and increased delivery of oxygen to the alveoli.
    B. increase respiratory rate, and it accompanies and increased level of carbon dioxide in the blood.
    C. decrease respiratory rate, and it accompanies increased synthesis of hemoglobin.
    D. decrease respiratory rate, and it accompanies reduced synthesis of carbonic acid.
    B. Decreased blood pH may arise from an increased level of carbon dioxide in the blood. High carbon dioxide concentration promotes the formation of carbonic acid, which dissociates into hydrogen ions and bicarbonate ions, reducing blood pH. The respiratory center of the medulla oblongata responds by increasing respiratory rate. The respiratory center is most sensitive, however, to blood carbon dioxide levels. An increased carbon dioxide concentration raises respiratory rate, and decreased carbon dioxide concentration reduces respiratory rate.
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  370. Sing out loud...
    Pump, pump,
    pump, pump,
    pump, pump,
    pump, pump, pump, pump,
    pump, pump,
    pump, pump,
    pump, pump,
    pump, pump, pump, pump,
    pump, pump,
    pump, pump,
    pump, pump, pump, pump, pumps your blood...
    • The right atrium's
    • where the process begins,
    • Where the C02 blood enters the heart
    • Through the tricuspid valve
    • to the right ventricle
    • The pulmonary artery and lungs.
    • Once inside the lungs it dumps its carbon dioxide
    • And picks up its oxygen supply
    • Then it's back to the heart through the pulmonary vein
    • Through the atrium and left ventricle.


    • The aortic valve's where the blood leaves the heart
    • Then it's channeled to the rest of the bod
    • The arteries, arterioles, and capillaries too
    • Bring the oxygenated blood to the cells
    • The tissues and the cells trade off waste and CO2
    • Which is carried through the venules and the veins
    • Through the larger vena cava to the atrium and lungs
    • And we're back to where we started in the heart.

  371. Which of the following correctly describes the order in which blood travels through the chambers of the heart?
    A. Right ventricle, left ventricle, right atrium, left atrium
    B. Left atrium, right atrium, left ventricle right ventricle
    C. Right ventricle, right atrium, left ventricle, left atrium
    D. Left atrium, left ventricle, right atrium, right ventricle
    D. It can be answered by naming any of the cardiac chambers first, as long as the remaining three chambers are listed in the appropriate order. This choice selects the left atrium as starting point and then correctly orders the remaining three.
    (this multiple choice question has been scrambled)
  372. Which of the following is true regarding human circulation?
    A. The pulmonary and systemic circulations are parallel but separate and nonintersecting.
    B. The systemic circulation delivers blood to the entire body with the exception of the lungs.
    C. Pulmonary circulation branches off the systemic circulation in the right side of the heart, where it then travels to the lungs.
    D. Pulmonary and systemic circulations comprise one continuous circulation.
    D. Pulmonary and systemic circulations constitute two components of a continuous loop. The choice that states "they systemic circulation delivers blood to the entire body with exception to the lungs" confuses the fact that the pulmonary circulation travels to the lungs with the fact that systemic circulation eventually feeds capillary beds throughout the body. The lungs have two separate capillary beds. In the pulmonary circulation, capillaries bring deoxygenated blood to the alveoli for gas exchange, and in the systemic circulation, capillary beds bring oxygenated blood to the alveoli to provide the lung tissues with oxygen. The other two choices contradict the notion of a continuous circulation.
    (this multiple choice question has been scrambled)
  373. Edema, an abnormal increase in fluid content in the interstitial spaces surrounding capillary beds, is manifested clinically as swelling. Describe the mechanisms that might produce edema.
    • Edema is caused by disruption of the hydrostatic/oncotic pressure dynamics and/or compromise of the vessel membrane integrity. Either condition can arise in both capillaries and lymph vessels. When lymph vessels are affected, normal drainage of tissue fluid is disturbed. An increase in hydrostatic pressure forces fluid out of capillaries; the capillaries then fail to reabsorb the fluid in adequate amounts.
    • Dimished capillary oncotic pressure reduces the blood's tendency to draw fluid back from the interstitium into the capillary. Insufficient plasma concentrations of albumin reduces the blood's ability to draw water inward across the capillary membrane, and edema results. Disruption of capillary wall integrity, precipitating loss of plasma proteins, reduces the ability of the vessels to hold and resorb fluid, causing edema
  374. Lymphatic vessels carry fluid called what? The lymphatics create an alternative/accessory route by which fluid remaining in the interstitum makes its way makes its way back to where?
    Lymph; makes its way back to the venous system and then to the heart's right atrium.
  375. From the lower body parts and from the left side of the upper body parts, lymph empties ultimately into the what?
    the thoracic duct, which, in turn, empties into the venous system at the junction of the left internal juglular and subclavian veins.
  376. From the right side of the upper body parts, lymph empties into the what?
    the right lymphatic duct, which, in turn, empties into the venous system at the junction of the right internal juglular and subclavian veins.
  377. What do lymph nodes contain?
    • They contain a concentration of lymphocytes, which fight infection.
    • Note: Lymphocytes also circulate freely in the blood stream.
  378. To what system do the spleen and the thymus belong?
    The lymphatic system.
  379. Where is the spleen located and what is its function?
    The spleen is located under the stomach and functions much like a large lymph node, except that the spleen acts as a lymphatic filter for blood while lymph nodes filter the lymph fluid. In addition, the spleen destroys senescent (aged) erythrocytes.
  380. Where is the thymus located, when is it most active, and what is its function?
    Found in the middle of the upper chest, the thymus is a small lymphoid organ that is especially active between birth and puberty. T-lymphocytes mature in the thymus, which degenerates during adolescence and adulthood, becoming largely nonfunctional.
  381. What are lymphocytes and what classes may they be broadly divided into?
    • Lymphocytes are a class of white blood cell (leukocyte).
    • They are broadly divided into two classes- T lymphocytes (T cells) and B lymphocytes (B cells).
  382. What are T cells?
    • T cells are the basis of cell-mediated immunity.
    • They have their origins in the bone marrow but mature in the thymus.
  383. What are the subtypes of T cells?
    • helper
    • suppressor
    • killer T cells
  384. What are B cells?
    • They originate in the bone marrow.
    • They participate in humoral immunity by producing antibodies, which belong to a class of proteins called immunoglobulins.
  385. When is the humoral immune system mobilized?
    When an antigen, a foreign particle or a portion of an invading organism, triggers the production of antibodies by specialized B cells known as plasma cells. The antibodies bind to antigens and mark them for destruction by other immune cells.
  386. Which of the following is a true statement?
    A. Leukocytes include lymphocytes and other cell types.
    B. T cells and B cells reside in the marrow, where immunoglobulins proliferate.
    C. T cells provide humoral immunity, and B cells provide cell-mediated immunity.
    D. Killer T cells kill B cells as a mechanism of regulating immune function.
    A. Lymphocytes are a subclass of leukocyte. The statement "killer T cells kill B cells as a mechanism of regulating immune function" is incorrect because the normal function of killer T cells is directed against foreign substances, not against other immune cells. Both T cells and B cells have their origins in the bone marrow, but once they mature they do not normally reside there, as one choice incorrectly suggests. (T cells mature in the thymus.) The reverse of the statement "T cells provide humoral immunity, and B cells provide cell-mediated immunity is true--correctly stated, B cells provide humoral immunity and T cells provide cell-mediated immunity.
    (this multiple choice question has been scrambled)
  387. Macronutrients (which are found in both liquid and solid foods) can be grouped into three types. List those three types.
    • carbohydrate
    • protein
    • fat
  388. Digestion is of two types. List those types and describe each.
    • Mechanical: mechanical digestion begins with the shredding and grinding of food into small pieces by chewing (mastication). It continues with vigorous churning in the stomach.
    • Chemical: chemical digestion occurs by means of enzymes produced by several different organs associated with the alimentary canal. Enzymes break down food into absorbable molecules.
  389. As food is chewed, it mixes with saliva. What digestive enzyme does saliva contain?
    • Salivary amylase
    • It initiates the digestion of starch, hydrolyzing glycosidic bonds to produce component sugars
  390. Transit through the esophagus results from a highly coordinated series of contractions, involving both circular and longitudinal muscles. What are these muscles called?
    peristalsis - which continues throughout the gastrointestinal tract
  391. Hydrochloric acid (HCl) is secreted into the stomach's lumen by specialized cells. What are these cells called?
    Parietal cells
  392. What stimulates the production and secretion of HCl in the stomach?
    The vagus nerve
  393. To what is the acidity of the stomach essential?
    the functioning of the gastric enzyme pepsin
  394. What secretes the gastric enzyme pepsin?
    chief cells
  395. What does pepsin initiate?
    the chemical breakdown of proteins
  396. Once food has been churned and digested by pepsin, through what does it pass?
    it passes through the pyloric sphincter into the first section of the small intestine, the duodenum
  397. What are the primary digestive functions of the mouth, esophagus, and stomach? What enzymes, if any, are associated with each?
    • Mouth: mastication; it secretes amylase-containing saliva, which begins the digestion of starch.
    • Esophagus: transports food from the mouth to the stomach through the synchronized muscular contractions called peristalsis.
    • Stomach: initiates protein digestion (and performs mechanical digestion). The parietal cells within the walls of the stomach secrete hydrochloric acid, rending the lumen highly acidic (pH between 1.5-2.5). The chief cells of the stomach secrete pepsinogen, which is converted to its active form-pepsin-by hydrochloric acid. Pepsin breaks down proteins.
  398. What is the liquid food mixture called in the small intestine?
  399. How is chime processed?
    It is processed by enzymes that act on protein, carbohydrate, and fat.
  400. Where are the enzymes of the small intestine synthesized?
    in a separate organ - the pancreas
  401. Through what are the pancreatic enzymes delivered directly to the duodenum?
    Via the pancreatic duct
  402. Some pancreatic enzymes are secreted into the small intestine in an inactive form. What are these inactive precursors called and how are they activated?
    • They are called zymogens.
    • To be activated, zymogens normally must be cleaved by an enzyme. (For example, among the zymogens released into the intestine is trypsinogen. The pancreatic enzyme trypsinogen is activated by an enzyme in the duodenum called enterokinase (also called enteropeptidase). The activation process produces trypsin, an active protein-degrading enzyme. Trypsin cleaves a number of other zymogens into their active forms.)
  403. Give the name and targets of three or four pancreatic enzymes.
    • Pancreatic amylase: (chemically identical to salivary amylase) continues the digestion of carbohydrates, which was initiated in the mouth.
    • Pancreatic lipase: serves in the enzymatic breakdown of fats (lipids).
    • Trypsin and chymotrypsin: the two most important proteolytic, or protein-digesting, enzymes in the gastrointestinal tract. These two enzymes break peptide bonds, reducing large proteins into small chains composed of only a few amino acids.
  404. Food particles are broken down by digestive enzymes into smaller subunits, which enter the blood stream by being absorbed across the wall of the small intestine into regional capillaries. From the small intestine, where does the blood travel?
    The blood travels directly to the liver, where further processing occurs.
  405. Characterize a zymogen.
    zymogen is a digestive enzyme's inactive precursor. It prevents the exposure of non-target material, that is, the pancreas itself, to the digestive function of an active enzyme (or, in some cases, modification by acid). Cleavage by another enzyme activates a zymogen. The pancreatic enzyme trypsinogen, for example, is a zymogen; its active form is trypsin.
  406. Pancreatic enzymes are secreted into the:
    A. stomach.
    B. small intestine.
    C. liver.
    D. pancreas.
    B. The question asks you to distinguish the origin of the pancreatic enzymes from their site of action. Pancreatic enzymes are produced in the pancreas and secreted through the pancreatic duct into the duodenum of the small intestine.
    (this multiple choice question has been scrambled)
  407. What is bile?
    • Active in the duodenum, it is produced in the liver and stored in the gall bladder.
    • It is a complex mixture of water, electrolytes, cholesterol, bilirubin, steroid hormones, and several other substances.
    • Containing no enzymes, it acts as an emulsifier, helping to separate large globules of fat molecules into smaller lobules in order to increase the surface area available for the action of lipase.
    • It enters the midsection of the duodenum via the common bile duct.
  408. Give the important functions of the liver.
    • Bile production
    • Plays a significant role in carbohydrate metabolism (for example, converting glucose to a storage form, glycogen), converts amino acids to keto acids and urea, and processes toxins.
    • Degradation of senescent (aged) erythrocytes.
  409. Which of the following statements is true?
    A. Bile has no enzymatic activity in the digestive system.
    B. The gall bladder produces bile, which enzymatically degrades fats.
    C. Bile enters the gall bladder for storage via the common bile duct.
    D. The gall bladder produces bile, which emulsifies fats.
    A. Bile emulsifies fats-it reduces large globules of fats into smaller globules in order to prepare them for digestion by lipase. The two choices that start by mentioning the gall bladder mistake the gall bladder for the liver, which is the site of bile production. Additionally, the choice that states the gall bladder's bile enzymatically degrades fats wrongly describes the role of bile as that of enzymatic degradation. The choice that starts by stating that bile enters the gall bladder is incorrect because the common bile duct conducts bile into the duodenum of the gall bladder; it is the cystic duct that carries bile to the gall bladder for storage.
    (this multiple choice question has been scrambled)
  410. What is the most important function of the large intestine and how does the soft, watery mixture of indigestible and nonabsorbable food that reaches the end of the small intestine pass through to the large intestine or colon?
    • The resorption of large amounts of water from its lumen
    • By passing through the ileocecal valve
  411. What are the important functions of bone?
    • Major component of the skeleton, providing an anchor for muscular contraction
    • Structural support and protection for organs and nerves
    • Red blood cells and platelets are formed in bone marrow
    • A storage depot for calcium, phosphate and other ions of biological significance (takes up and releases as needs)
    • Maintain a variety of ion concentrations within acceptable limits
  412. What type of tissue is bone and of what is it principally composed? What is the crystalline compound of calcium and phosphorous found in bone called?
    • Dynamic connective tissue; a living tissue
    • Matrix (which is composed of organic, like Type I collagen and amorphous ground substance (glycosaminoglycans and proteins), and inorganic, like calcium and phosphorous, substances in about a 1:1 ratio) and cells
    • Hydroxyapatite
  413. Bone is a living tissue with three different cell types. List and describe each type.
    • Osteoblasts: located on the inner surfaces of bone tissue, synthesize Type I collagen and other organic components of the matrix, build and nourish bone
    • Osteocytes: occupy minute spaces (lacunae) within the bony matrix, are simply osteoblasts with greatly reduced synthetic capacity, are responsible for maintaining the matrix, build and nourish bone
    • Osteoclast: also known as a multinucleated giant cell, promotes ongoing breakdown, resorption, and remodeling of bone.
  414. Chemical removal of either the mineral or the organic substance of bone leaves the bone in its original shape but alters its mechanical properties. What changes would be produced by the removal of the mineral component? The organic component?
    • The mineral composition of bone is largely a crystalline substance called hydroxyapatite. Dissolution of the mineral component would make the bone softer and more flexible.
    • (Collagen, composed of protein chains, can be correctly presumed to impart some flexibility to the bone.)
    • The removal of the organic component of the bone matrix results in an inflexible, hard, brittle substance, subject to destruction under force.
  415. Gross examination of cut bone reveals two distinct bone morphologies. Describe each.
    • Compact: the outer, dense portion
    • Spongy bone: the inner spongy-looking area (due to its many small, marrow-filled cavities)
    • Despite differences in their gross appearances, compact bone and spongy bone are similarly constituted. Each consists of matrix and cells.
  416. What are the two types of bone marrow? What is the difference between newborn marrow and adult?
    • Red: the site of red blood cell and platelet production and some immune cell development and maturation
    • Yellow: filled with adipocytes (fat cells)
    • In addition to the osteoblasts, osteocytes, and osteoclasts, other cell species inhabit the marrow.
    • Newborn: all marrow is red
    • Adult: red marrow is confined primarily to flat bones, such as ribs, clavicles, pelvic bones, and skull bones. Under stress of blood loss or poor oxygen supply, however, yellow marrow may be transformed into red marrow to increase red blood cell production.
  417. On microscopic examination, a cross section of compact bone shows several sets of concentric lamellae (rings). What is each set of concentric lamellae, running parallel to the bone's long axis? What is their purpose?
    • Haversian system, or osteon.
    • Haversian systems exist to distribute nutrients throughout compact bone. Many Haversian systems together give compact bone its strength.
  418. What is at the center of each Haversian system and what is its purpose?
    • At the center of each Haversian system is a canal known as a Haversian canal.
    • A Haversian canal runs the length of a Haversian system.
    • This canal carries blood vessels and nerves, and its filled with loose connective tissue.
    • Shallow indentations mark the surfaces of the lamellae
  419. What are the thin segments of bone that surround the many small marrow spaces in the spongy bone? What is their purpose?
    • Spicules
    • Because of their thinness, the spicules within spongy bone are able to absorb nutrients directly from the marrow contained within their cavities, and so do not require Haversian systems for nutrient delivery
  420. In what ways are compact bone and spongy bone similar? Dissimilar?
    • Compact bone and spongy bone are similar in that:
    •    They have the same chemical and structural composition
    •       both are composed of matrix and bone cells
    •       both are hard and resistant to bending or compression
    • The essential difference between compact bone and spongy bone:
    •    The manner in which the components are arranged
    •      Compact bone is so densely arranged that the canals of the Haversian systems are required to convey nutrients to its cells
    •      The hard substance of spongy bone is laid out in thin, bubble-like form that precludes the need for special nutrient delivery channels
  421. Hydroxyapatite and collagen are the principal components of:
     A. hard bone matrix.
     B. Haversian canals.
     C. cartilage matrix.
     D. lacunae.
    A. Osteoblasts secrete bone matrix, containing mostly collagen. The bone matrix then becomes hardened when hydroxyapatite is deposited at the site. The choice of Haversian canals is in correct because Haversian canals are found at the center of Haversian systems within compact bone. Blood vessels and nerves run through the Haversian canal. Cartilage matrix is incorrect as well; Cartilage matrix is composed of collagen and proteoglyeans. Lacunae is incorrect because lacunae are small cavities or wells. Cartilage cells (chondrocytes) and bone cells (osteocytes reside in the lacunae.
  422. Which of the following applies to osteoclasts?
     I. They are multinucleated cells.
     II. They are a type of bone cell.
     III. They deposit new bone during bone remodeling.

     A. II only
     B. I and II only
     C. II and III only
     D. I, II, and III
    B. is correct.
  423. Describe the three classes of joints. What are the purposes of ligaments and tendons?
    • Joints allow for motion and flexibility.
    • Fibrous: composed of collagen fibers, designed to allow minimal movement
    • Synovial: consists of the approximated ends of two bones (nearly in contact, covered with smooth, tough articular cartilage), covered with a common synovial capsule made of fibrous tissue (encloses a sac of synovial fluid that acts as a lubricant, which, with the underlying articular cartilage, allows smooth movement of the joint, protecting the bones from damage that might otherwise result from friction); allow for the great range and extent of movement seen in the body; examples include knees, hips, shoulders, and fingers
    • Cartilaginous: articular cartilage

    • Ligaments: keep bones attached to joints
    • Tendons: attach muscles to bones
  424. What are the three types of muscles that are based on the microscopic structure? Describe each types contraction.
    • skeletal:
    •    Voluntary contraction - A skeletal muscle that traverses a joint will be among those responsible for bending that joint (like biceps brachii, traversing the elbow joint, which is antagonistic to the triceps).
    • cardiac:
    •      operates involuntarily (sinoatrial node initiates contractions)
    • smooth:
    •      Involuntarily controlled, the operative muscle of organs and systems such as blood vessels, stomach, intestines, skin, glands and ducts.
  425. What should be known physiologically about an exercising muscle?
    An exercising muscle is acidic (because of (i) the accumulation of lactic acid and (ii) the high partial pressure of carbon dioxide which results in an increase carbonic acid), hot (because of the increased metabolic rate and blood flow) and has a high partial pressure of carbon dioxide; an exercising muscle requires increased quantities of oxygen.
  426. Describe the skeletal muscle cell.
    • a long, multinucleated cell in which many striations are visible
    • commonly referred to as muscle "fibers" or myofibers
    • A group or bundle of skeletal muscle fibers is referred to as a fascicle
  427. What is a sarcomere?
    a segment of muscle fiber between two Z lines

    •                  |-----A Band-----|-I Band-|
    •         ___________    ____________
    • -----⟨_____>->->-(--)-<-<-<______⟩-----
    • -----⟨_____>->->-(--)-<-<-<______⟩-----
    • -----⟨_____>->->-(--)-<-<-<______⟩-----
    •    Z line               |-H-|                 Z line
  428. What is a sarcomere composed of and describe each?
    • Myosin filament (thick filaments) that have no connection to the Z lines - The length of myosin filament corresponds to the A band. Because the filament itself does not contract, the A band has a fixed length equal to that of the myosin strands. The center of the sarcomere, containing only myosin filaments with no overlapping actin filaments , is the H zone.
    • Actin filaments (thin filaments) that are anchored at one end to a Z line - A given length of thin filament that does not overlap with any thick filament is called the I band.
    • Myosin and Actin are proteins
    • Contraction is achieved by the sliding of actin and myosin filaments, each over the other

    •                  |-----A Band-----|-I Band-|
    •         ___________    ____________
    • -----⟨_____>->->-(--)-<-<-<______⟩-----
    • -----⟨_____>->->-(--)-<-<-<______⟩-----
    • -----⟨_____>->->-(--)-<-<-<______⟩-----
    •    Z line               |-H-|                 Z line
  429. Describe the sliding filament mechanism that occurs in order for a muscle to contract.
    • Regularly spaced crossbridges extend from the myosin filaments to the actin filaments.
    • These crossbridges make the physical interaction possible
    • 1) the myosin head binds to the actin filament at a myosin binding site
    • 2) the myosin heads interact with the actin filaments in such a way as to draw them inward so that Z lines come closer together and the sarcomere shortens.
  430. All human cell membranes operate an energy-dependent sodium-potassium pump (Na+-K+ ATPase) that continuously pumps potassium ions into the cell and sodium ions outward. For every 2 K+ pumped in, 3 Na+ are pumped out. What does result in?
    • Membrane resting potential: the inside is negative relative to the outside
    • (1) Na+ concentration is higher outside the cell than inside
    • (2) K+ concentration is higher inside the cell than outside
    • (3) the cell's interior is electrically negative relative to its exterior
  431. What is an action potential in a muscle cell (or a nerve cell)?
    • A wave of depolarization that spreads rapidly and extensively along the entirety of the cell membrane so that the whole of the cell is depolarized (a rapid influx of sodium ions results). The entire cell reverses its normal charge gradient and its inside becomes positive relative to its outside. After depolarization, it loses its increased permeability to sodium and temporarily experiences and increased permeability to potassium, restoring the original resting potential.
    • Often used to designate the combination of the two sequential events:
    • (1) rapid depolarization followed by
    • (2) repolarization
  432. What are the regulatory proteins intimately associated with actin molecules within the myofiber's sarcomeres? Describe their part in muscle contraction.
    • Tropomyosin: in a resting muscle, these molecules "mask," or "cover," those sites on the actin molecule with which myosin heads are prone to interact.
    • The troponin complex: Troponin has a tendency to bind calcium ions, if they are present, and then undergoes a change of shape and position to cause the tropomyosin molecule to "uncover" the actin sites with which myosin is prone to interact.
    • Therefore: If the myofiber's troponin complex is exposed to calcium ions, the actin and myosin interact at their crossbridges, the sarcomere shortens, and the fiber contracts.
  433. Within a myofiber (muscle cell), the:
    (1) cell membrane is called the __________;
    (2) cytoplasm is called the __________;
    (3) endoplasmic reticulum is called the ___________ ________, which stores ______ ____ in a muscle; and
    (4) __________ and _________ _________ are roughly continuous with each other.
    • (1) cell membrane is called the sarcolemma;
    • (2) cytoplasm is called the sarcoplasm;
    • (3) endoplasmic reticulum is called the sarcoplasmic reticulum, which stores calcium ions in a muscle (Ca2+); and
    • (4) sarcolemma and sarcoplasmic reticulum are roughly continuous with each other.
  434. Muscle contraction proceeds from the following series of events:
    (A) A motor neuron that innervates the myofiber undergoes ________ and __ _______ _______, causing the motor neuron to release the neurotransmitter _________.
    (B) The neurotransmitter binds to receptors on the ___________, which is continuous with the _________ ___________.
    (C) The neurotransmitter causes depolarization of both __________ and __________ __________.
    (D) The depolarization, if sufficient in magnitude, triggers an action potential, and the entire __________ depolarizes.
    (E) The action potential causes ______ _____ to move from the ________ ________ to the _______ ____, surrounding the fiber's actin and myosin filaments.
    (F) The ________ ____ bind to troponin.
    (G) This binding causes _____________ to undergo change in shape and position.
    (H) The sites at which ______ interacts with _________ are "uncovered." _______ heads are thus able to contact ______ filaments.
    (I) _______ and ________ interact as "sliding filaments."
    • A. A motor neuron that innervates the myofiber undergoes depolarization and an action potential, causing the motor neuron to release the neurotransmitter acetylcholine.
    • B. The neurotransmitter binds to receptors on the sarcolemma, which is continuous with the sarcoplasmic reticulum.
    • C. The neurotransmitter causes depolarization of both sarcolemma and sarcoplasmic reticulum.
    • D. The depolarization, if sufficient in magnitude, triggers an action potential, and the entire sarcolemma depolarizes.
    • E. The action potential causes calcium ions to move from the sarcoplasmic reticulum to the sarcoplasmic space, surrounding the fiber's actin and myosin filaments.
    • F. The calcium ions bind to troponin.
    • G. The binding of calcium ions to troponin causes tropomyosin to undergo change in shape and position.
    • H. The sites at which actin interacts with myosin are "uncovered." Myosin heads are thus able to contact actin filaments.
    • I. Actin and myosin interact as "sliding filaments."
  435. In simple terms, list the order of events in muscle contraction, beginning with a nerve impulse to the muscle.
    • A nerve impulse arrives at the neuromuscular junction, causing the release of acetylcholine.
    • Depolarization of muscle cell membranes is carried throughout the fiber by the T tubules.
    • The depolarization causes a release of calcium ions, which bind to troponin on the actin filaments.
    • This causes a conformational change that uncovers myosin binding sites on the actin filaments. Myosin crossbridges are then able to attach to the actin and flex, pulling the actin fiber along the myosin fiber. This causes the simultaneous shortening of sarcomeres all along the muscle cell.
  436. When does muscular function require energy?
    • To maintain-
    • (1) the resting potential that allows for depolarization and action potential
    • (2) the dynamic interaction of myosin and actin that underlies the physical shortening of the sarcomere, and
    • (3) the return of calcium ions from the sarcoplasm to the sarcoplasmic reticulum after contraction is complete
  437. Myofibers store relatively small amounts of phosphocreatinine. What is the purpose of this molecule?
    • It embodies a high-energy phosphate bond.
    • Used to regenerate ATP from ADP and inorganic phosphate
  438. Examined under a microscope, myocardium differs from skeletal muscle most notably in the appearance of dark lines. What are these dark lines called? Describe their role in the myocardium.
    • Intercalated discs
    • The attachment points between adjacent muscle cells.
    • The attachments, gap junctions, allow a nearly unimpeded flow of ions from one fiber to the next (so the action potential created in one cardiac cell is easily and readily propagated to the next).
    • The whole of the cardiac muscle mass, the myocardium, is termed a syncytium (in which rapid intercellular transmission of action potentials promotes a particularly organized and synchronous mode of contraction)
  439. How is the arrangement of actin and myosin filaments different in smooth muscles than in skeletal and cardiac cells?
    The absence of striations relates to the arrangement of actin and myosin filaments that are not as regular in smooth muscle fibers as in skeletal and cardiac cells.
  440. Smooth muscle contracts according to a mechanism that resembles those of skeletal and cardiac muscles. Contraction is triggered by an action potential that releases calcium ions from the sarcoplasmic reticulum. Yet, there is a difference with the smooth muscle. Explain.
    • Tropomyosin and troponin complex are absent.
    • Calcium ions induce contraction by some device different than that which operates in the sarcomeres of skeletal and cardiac muscle.
    • Calcium ions bind to a calcium-binding protein called calmodulin.
    • The calcium-calmodulin complex then interacts with a protein called myosin light chain kinase (MLCK) which, in turn, directly phosphorylates the myosin head.
    • Phosphorylation of the myosin head then allows myosin to form a cross bridge with actin, whereupon contraction occurs
    • Like cardiac muscle, adjoining smooth muscle cells feature gap junctions so that the action potential is readily and rapidly transmitted from one cell to the next.
  441. Identify the muscle type that characterizes these organs or structures: wall of the right ventricle, wall of the gall bladder, wall of the large artery in the quadriceps, the quadriceps, the diaphragm, and the iris of the eye.
    The wall of the right ventricle and the other cardiac chambers are the only sites at which cardiac muscle is found. The walls of the gall bladder, of arteries throughout the body, and the iris are all composed of smooth muscle fibers. The quadriceps and the diaphragm are both composed of skeletal muscle.
  442. What are the four important roles the kidneys play in helping the body maintain homeostasis?
    • (1) Excretion of hydrophilic waste; note that the liver is responsible for excreting hydrophobic or large waste products which cannot be filtered by the kidney.
    • (2) Maintain constant solute concentration.
    • (3) Maintain constant pH (approximately 7.4).
    • (4) Maintain constant fluid volume, which is important for blood pressure and cardiac output.
  443. What are the two portions of the kidneys visible on gross examination?
    • Renal cortex: an outer portion
    • Renal medulla: an inner portion (composed of wedge-shaped tissue structures called the renal pyramids, or medullary pyramids.)
  444. What is the innermost portion of the kidney which the medulla and cortex wrap around? Where is this located? What is this?
    A hollow renal pelvis; located in the kidney's hilus, is actually an extension and expansion of the ureter, which leads to the urinary bladder
  445. What is the basic structural and functional unit of the kidney? Describe these.
    • The nephron (each kidney consists of more than a million)
    • Each consists of a renal corpuscle, continuous with a long "urinary pipeline," or renal tubule (a hollow tube surrounded by epithelium cells)
  446. The renal corpuscle is comprised of three elements. Name them and describe each.
     What does this area of the nephron function as?
    • Glomerulus: a tuft of capillaries
    • A glomerular basement membrane
    •  A surrounding Bowman's capsule: a double-walled cup formed as an enlargement of the proximal end of the renal tube.
    •  This area of the nephron functions in blood filtration.
  447. After the Bowman's capsule, the renal tubule follows a twisting course, conventionally partitioned into five major segments. List those segments.
    • the proximal convoluted tubule (at the beginning in cortex)
    • the descending loop of Henle (extends into the pyramids)
    • the ascending loop of Henle (back up into the cortex)
    • the distal convoluted tubule
    • the collecting duct (back into the medullary pyramids, a single duct carries fluid away from numerous distal convoluted tubules.
  448. What is formed from many collecting ducts and where is it emptied?
    • Papillary ducts; they empty into the funnel-shaped sections of the renal pelvis called calyces (singular: calyx)
    •  From there, the ureter carries the wine away from the kidney to the urinary bladder, where it is stored until it passes from the body in micturition (urination).
  449. Urine passes directly to the outside of the body through which of the following structures?
    A. The renal tubule
    B. The urethra
    C. The ureter
    D. The collecting duct
    B. The urethra passes from the bladder to the outside of the body; it is from here that urine is excreted. A ureter passes from each kidney to the bladder (the ureter is incorrect). Collecting ducts channel urine to the renal pyramids, which are still far from the point of excretion from the body (the collecting duct is incorrect). The renal tubule refers to the portion of the nephron beginning immediately distal to the renal corpuscle (the renal tubule is incorrect).
    (this multiple choice question has been scrambled)
  450. How is the blood to be filtered by the kidney delivered?
    • via the renal artery, which branches off the abdominal aorta
    •  the artery branches in to afferent ("approaching") arterioles which travel to individual renal corpuscles, where they branch profusely to form the glomerular capillaries inside a Bowman's capsule.
  451. Describe the physical characteristics of the Bowman's capsule.
    • The inner wall (or visceral layer) is porous and permeable to plasma and other small blood constituents.
    • The exterior wall of the capsule (parietal layer) is neither porous nor permeable.
    • The space enclosed by the two walls-the Bowman's space- is the origin of the renal tubule.
  452. Which of the following laboratory findings would most likely indicate disease?
     A. The absence of large proteins in the urine.
     B. The absence of white blood cells in the urine.
     C. The presence of red blood cells in the urine.
     D. The presence of hydroxide ions in the urine.
    C. Blood coursing through the glomerular capillaries is filtered through the capillary walls into Bowman's capsule. The filtrate contains a great many constituents of blood (water, amino acids, glucose, ions, urea, and other small molecules), but t does not contain blood cells. The presence of red blood cells in the urine (hematuria) is abnormal and a possible indication of disease. The urine does not normally contain large proteins or white blood cells; it does contain hydroxide ions.
  453. Which of the following is an INCORRECT statement?
     A. Glomeruli are continuous with the proximal convoluted tubule.
     B. The proximal convoluted tubule is continuous with the distal convoluted tubule.
     C. The ureter empties into the bladder.
     D. Distal portions of each nephron coalesce to ultimately form a structure that is continuous with the ureter.
    A. The glomerulus is a capillary bed, which, together with Bowman's capsule, constitutes the renal corpuscle. The glomerulus is not continuous with Bowman's capsule. Rather, certain blood constituents pass through the walls of the glomerular capillaries to reach Bowman's capsule. Bowman's capsule is continuous with the proximal convoluted tubule, which is continuous with the descending limb of the loop of Henle, which is continuous with the ascending limb of the loop of Henle, which is continuous with the distal convoluted tubule, which is continuous with the collecting duct. The collecting ducts coalesce to form papillary ducts, which, in turn, ultimately join to form the renal pelvis. The renal pelvis is continuous with the ureter, and the ureter empties into the bladder.
  454. Which of the following choices correctly characterizes the glomerulus?
     A. It is composed primarily of nervous tissue.
     B. It is composed primarily of blood vessels.
     C. There is one per kidney.
     D. It is situated distal to Bowman's capsule.
    B. The glomerulus is a tuft of capillaries, and capillaries are blood vessels. Blood is filtered through the glomerulus into Bowman's capsule, which means that the glomerulus is proximal (not distal) to Bowman's capsule. There is one glomerulus associated with each nephron, which means that there are many glomeruli (not one) associated with each kidney.
  455. What does the kidney reabsorb from the glomerular filtrate, where does reabsorption occur, and what is it called when certain waste molecules are added to the filtrate?
    water, ions, and other useful substances; some occurs along the entire length of a nephron, but 75% happens at the proximal convoluted tubule; secretion
  456. Describe fluid transport through the loop of Henle.
    • The Descending Loop of Henle: The salt concentration of the cortical interstitial fluid-around the renal corpuscles, proximal convoluted tubules, and upper portion of the loop of Henle- is relatively low. As filtrate travels through the descending loop of Henle, it encounters increasingly higher salt concentrations in the surrounding interstitial environment. Because the wall of the descending limb of the loop of Henle is permeable to water but nearly impermeable to solutes, water passes out of the loop of Henle. Therefore, water is reabsorbed back into the body in the descending loop of Henle.
    •  The Ascending Loop of Henle: the concentration gradient is reversed here (it decreases) but the ascending limb is impermeable to water and permeable to sodium. As the filtrate travels here, it becomes dilute once again.
  457. The water that diffused out of the tubule walls of the loop's descending limb has been essentially trapped within the surrounding interstitial space. Through what blood vessels will this water be reabsorbed?
    the vasa recta, which are continuous with the renal vein
  458. The kidney maintains a concentration gradient in its interstitial fluid, with the concentration of sodium and other ions increasing several fold from the cortex to the medulla. Discuss this gradient in relation to the composition of filtrate in the descending loop of Henle.
    Water will diffuse across a membrane to equalize ionic concentrations on both sides of the membrane. In the descending limb of the loop of Henle, the filtrate encounters a progressively increasing concentration of solute across the tubule membrane as it travels toward the medulla. Thus, water from the filtrate diffuses across the loop membrane into this surrounding interstitial fluid, which increases the concentration of tubular ions and dilutes the interstitial fluid. Despite this diluting effect of reabsorbed filtrate water, other mechanisms work to maintain the interstitial concentration gradient. Hence, the process of tubular filtrate concentration continues as it passes through the increasingly concentrated environment of the medulla near the hairpin loop.
  459. Which of the following choices properly characterizes fluid in the distal convoluted tubule?
     A. Its concentration of protein is markedly higher than that of proximal convoluted tubule.
     B. Its chlorine concentration is markedly lower than that of the proximal convoluted tubule.
     C. Its sodium concentration is markedly lower than that of the proximal convoluted tubule.
     D. Its volume is markedly less than that of the proximal convoluted tubule.
    D. The passage of filtrate through the loop of Henle and its limbs allows for the conservation of water. That is, a net movement of water occurs from the tubule outward into the interstitium. Although the tubule fluid experiences little change in its concentrations of solutes as it passes from descending to ascending limbs, it undergoes a pronounced diminution in volume. Protein molecules are not normally filtered through the glomerations into the tubular fluid. Protein concentration within the tubular fluid should be very nearly zero at all portions of the nephron. The presence of protein in the urine (proteinuria) is a classic sign of kidney disease.
  460. The permeability of the collecting tubule to water can be regulated depending on the body's need to conserve or eliminate water. How is this regulation accomplished?
    by antidiuretic hormone (ADH) or vasopressin, a peptide synthesized in the hypothalamus and secreted by the posterior pituitary (it increases the collecting duct's permeability to water; water moves outward from the duct to the interstitium and is conserved.)
  461. A woman preparing to undergo a sonogram drinks six 8-ounce glasses of water before the procedure. What will likely be the effect of her water intake on blood levels of ADH, a hormone released by her posterior pituitary?
    ADH increases the collecting duct's permeability to water, promoting water conservation. In this case, the patient is overhydrated. In order to reestablish homeostasis, she must excel a relatively large volume, so the posterior pituitary reduces its secretion of ADH.
  462. Which of the following choices does NOT accompany increased secretion of ADH?
     A. Decreased urine volume
     B. A more dilute wine
     C. Increased movement of water from collecting ducts to interstitium
     D. Water conservation
    B. ADH increases the collecting duct's permeability to water, causing (a) movement of water from the collecting duct to the interstitium; (b) the production of a concentrated urine, relatively low in volume; and (c) the concomitant conservation of water. ADH concentrates the urine; it does not dilute it.
  463. In the condition known as diabetes insipidus, ADH secretion is impaired. Among the following, which symptom will the patient most likely experience?
     A. Increased thirst
     B. Decreased thirst
     C. Low urine output
     D. High content of protein in the urine
    A. The absence of ADH will decrease the permeability of the collecting duct to water. Water will not more from the collecting duct to the interstitium, even in the face of relative dehydration. The patient will excrete relatively high volumes of dilute urine and will thus experience a tendency toward high salt concentrations and low volume of body fluids. If the patient's thirst mechanism is intact (as it normally is in diabetes insipidus) she/he will experience increased thirst and will compensate by drinking. In the absence of kidney disease, the wine will not contain protein; that is, in the healthy kidney, protein is not filtered out of the glomerulus.
  464. Which of the following choices is NOT characteristic of an endocrine gland?
     A. It secretes enzymes that act on distant organs or cells.
     B. It helps to maintain homeostasis.
     C. It secretes hormones that exert their effects at a distant site.
     D. It secretes hormones that are transported through the bloodstream to reach their sites of action.
    A. Endocrine glands secrete hormones into the bloodstream, while exocrine glands secrete their products to the external environment via ducts. Endocrine glands functioning the maintenance of homeostasis their hormones affect target cells and organs, in response to changes in internal and external bodily environments. Generally, hormones act at sites remote from the points at which they are released, and they reach their sites of action via the bloodstream.
  465. Which of the following findings would justify an investigator in classifying the adrenal glands as an endocrine organ?
     A. They are associated with the kidneys.
     B. They receive a large blood supply.
     C. They secrete a substance that can be used clinically as an anti-inflammatory agent.
     D. They secrete a substance that travels through the blood and affects the degree of protein catabolism in response to variable conditions.
    D. An endocrine organ is one that secretes hormones, which travel in the blood to their target sites, and control homeostasis. If the adrenal glands secrete a substance that travels through the blood to modulate protein catabolism, it secretes a hormone and is an endocrine organ.
  466. What are the eight major endocrine glands in humans?
    • the pancreas, the adrenal glands, the thyroid gland, the parathyroid glands, the ovaries, the testes, the hypothalamus, and the pituitary gland
    •  Note: this is not an exhaustive list; there are other organs (such as the thymus, heart, and kidney) that can also be classified as endocrine glands
  467. The pancreas is classified as:
     A. an endocrine gland.
     B. an exocrine gland.
     C. both an endocrine and an exocrine gland.
     D. neither an endocrine nor an exocrine gland.
    C. It is an exocrine organ because it secretes digestive-enzymes and bicarbonate into the lumen of the duodenum. These secretions come from acinar cells and empty via ducts into the gastrointestinal tract. It is an endocrine organ because it secretes hormones, three of which are insulin, glucagon, and somatostatin. All three are secreted by pancreatic islet cells located in the islets of Langerhans. Insulin (secreted by the β cells) and glucagon (secreted by the α cells) regulate glucose transport, storage, and metabolism. Somatostatin (secreted by the δ cells) inhibits many digestive processes.
  468. Give the two major sources that supply our body with glucose.
    • First, polysaccharides that we eat are chemically broken down and then absorbed by the gastrointestinal tract.
    •  Second, glucose can be produced by the liver and released into the blood.
  469. In the absence of insulin, most of the body cells are relatively impermeable to glucose. Give the exceptions.
    • The brain: the brain takes up glucose from the blood whether or not insulin is secreted.
    •  The liver: the liver converts large quantities of the glucose it takes up to glycogen, a long carbohydrate polymer that serves as a storage form of glucose.
  470. Overall, insulin has four main functions in the human body. List these.
    • 1. increasing cellular uptake of glucose  
    • 2 .promoting formation of glycogen from glucose in the liver
    • 3. reducing glucose concentration in the blood, and
    • 4. increasing protein and triglyceride synthesis
  471. What is glucagon?
    Glucagon promotes the breakdown of glycogen in the liver through a process termed glycogenolysis. That breakdown produces glucose, which is then released into the blood. Glucagons also promotes the manufacture of glucose ire the liver through a process called gluconeogenesis. Glueoneogenesis involves the synthesis of glucose-not from glycogen, but from lactate, amino acids, and triglycerides. This newly formed glucose is also released into the blood, so the most easily detectable effect of glucagon is an increase of the blood's glucose levels. Glucagons also increases lipolysis (lipid breakdown). It does NOT decrease cellular uptake of glucose.
  472. Which of the following is a pair of hormones secreted by the pancreas?
     A. Glycogen and glucose
     B. Insulin and glycogen
     C. Insulin and glucagon
     D. Amylase and lipase
    C. Insulin and gucagon are two of the hormones secreted by the endocrine cells of the pancreas into the blood. In contrast, the exocrine cells of the pancreas secrete digestive enzymes, including amylase and lipase, directly into the digestive tract via ducts. Glycogen is the storage form of glucose found predominantly in the liver.
  473. If a patient were to lose consciousness because his/her blood levees of glucose were low and his/her brain was receiving an inadequate supply of fuel, which of the following would be the best treatment?
     A. Administration of insulin
     B. administration of glucagon
     C. Administration of glycogen
     D. Administration of oxygen
    B. The patient has fallen unconscious because his/her brain has no source of glucose, which is required to produce the high-energy molecule ATP. In order to supply the brain with glucose, the physician must raise the glucose levels of the blood. Administration of glucagon will cause the liver to release glucose in the blood, making it available to the brain. Insulin administration would worsen the patient's condition since insulin tends to promote the uptake of glucose in cells, thus lowering blood glucose levels even further. Note that the condition described above often arises in diabetics who have received too much exogenous insulin.
  474. Among the following choices, which is most likely to produce hyperglycemia?
     A. A hepatic condition in which gluconeogenesis is impaired.
     B. A hepatic condition in which glucagon fails to exert its effects.
     C. A pancreatic condition in which glucagon is not secreted.
     D. A pancreatic condition in which insulin is not secreted.
    D. Hyperglycemia refers to excessive quantities of glucose in the blood. It can be caused by either excessive secretor of glucagon or impaired secretion of insulin (in most cases, it is produced by impaired secretion of insulin, as diabetes mellitus Type I). If gluconeogenesis were impaired, one potential source of blood glucose would be eliminated, and blood glucose levels would be reduced. The same is true for the remaining choices; suppression of glucagon function, by whatever means, would inhibit gluconeogenisis and glycogenolysis, thereby reducing blood glucose levels.
  475. Where do the adrenal glands sit in the human body and describe the two distinct regions that are developmentally and functionally distinct?
    An adrenal gland sits on each kidney (so humans had a left and a right adrenal gland. The two regions are related more in name than in function, and are termed the adrenal cortex and the adrenal medulla.
  476. Describe the adrenal cortex.
    It is the outer portion of the adrenal gland. It produces a class of endocrine hormones called corticosteroids, which are subdivided into three groups: the mineralocorticoids, the glucocorticoids, and the sex hormones.
  477. The mineralocorticoids affect levels of what in the body?
    What is the main mineralocorticoid secreted by the adrenal cortex and what does it act upon?
    What are the ultimate effects of this particular mineralocorticoid?
    What stimulates the secretion of this mineralocorticoid?
    • The levels of the minerals sodium and potassium in the body
    • Aldosterone
    • It acts primarily at the distal convoluted tubule of the kidney to promote sodium-potassium exchange (increasing the removal of three sodium ions from the renal filtrate for every two potassium ions transported into the filtrate and this promotes the movement of water form tubule to interstitium)
    • The effects are:
    • 1. increase urinary excretion of potassium,
    • 2. increase interstitial sodium concentration, and
    • 3. increase water conservation (as an effect of #2)
    • As a result, it is not surprising that aldosterone secretion is stimulated by high levels of extracellular potassium, low levels of extracellular sodium, and low fluid levels (blood volume).
  478. What do the glucocorticoids affect?
    What is the main glucocorticoid secreted by the adrenal cortex?
    What causes the release of this glucocorticoid and what controls the release?
    • Glucocorticoids affect: plasma glucose concentrations, increase blood glucose levels (especially in response to environmental stressors), strengthen cardiac muscle contractions, increase water retention, and have anti-inflammatory and anti-allergic activities.
    • Cortisol: released as part of the long-term stress response and affects most tissues in the body. It increases plasma glucose levels and inhibits immune activity.
    • Cortisol release is controlled by the hypothalamus and the anterior pituitary and causes negative feedback to both these areas of the brain.
  479. The adrenal cortex secretes low levels of the sex steroids. What is the name of the one most produced by the adrenal cortex?
    Androgens: the sex hormone dominant in men and the adrenal cortex is the main source of androgens in women (since women have no testes) and plays a role in sex drive.
  480. What does the adrenal medulla secrete? What is epinephrine?
    • catecholamines, mostly epinephrine (also known as adrenaline)
    • Epinephrine is an amino acid derivative that acts like a peptide hormone.
  481. Describe the thyroid and where it is located. What does it synthesize and secrete?
    • The thyroid is a flat gland located in the neck, in front of the larynx.
    • It synthesizes and secretes two hormones: calcitonin and the thyroid hormones (thyroxine- thyroid hormone T4, triiodothyronine- thyroid hormone T3)
  482. Describe the parathyroid glands, giving location and the hormone they secrete with its effects.
    • A set of four small glands located on the posterior aspect of the thyroid.
    • The peptide hormone parathyroid hormone (PTH, also known as parathormone) exerts effects opposite those of calcitonin (which is produced in the parafollicular cells of the thyroid). It is secreted in response to low blood levels of calcium, and through actions on various organs, it increases levels of blood calcium. It acts to:
    • 1. increase blood resorption and consequent calcium release,
    • 2. increase intestinal calcium uptake, and
    • 3. promote calcium re-uptake at the kidney.
  483. Describe the ovarian cycle.
    • follicular phase (the first phase):
    •   rapid growth of the ovarian follicule
    •   the anterior pituitary gland secretes two hormones (follicle-stimulating hormone (FSH) and luteinizing hormone (LH)) that stimulate the growth of one follicle containing several ova, only one of which fully matures
    •   the follicle itself is secretory, releasing the hormone estrogen as it develops
    •   the follicular phase ranges from seven to twenty-one days
    •   Increased ovarian estrogen release prevents maturation of more than one follicle at a time.
    •   at the end of the follicular stage (around day 14), there is a surge in LH secretion from the anterior pituitary causing the release of the ovum from the enlarged follicle (ovulation), and it is swept into the Fallopian tube by the fimbriae where the ovum waits for fertilization by sperm
    • luteal phase (the final phase):
    •   typically day 14 to day 28
    •   after ovulation, the part of the ruptured follicle that remains in the ovary is referred to as the corpus luteum
    •   the corpus luteum secretes estrogen and progesterone
  484. Describe the uterine cycle.
    • Menses (the first phase):
    •   shedding of the uterine lining
    •   lasts between 4 and 7 days and occurs at the same time as the early follicular phase in the ovary
    • Proliferative phase:
    •   occurs until day 14.
    •   estrogen from the ovaries induces the proliferation of the endometrium
    • Secretory phase (final phase):
    •   lasts for the final 14 days of the menstrual cycle
    •   progesterone from the corpus luteum promotes the rapid thickening and vascularization of the uterine lining in preparation for the implantation of a fertilized ovum - 
    •      if the mature ovum is not fertilized, it will not implant into the uterine lining
    •      at approximately 13 days after ovulation (day 27), the corpus luteum in the ovary degenerates and ceases to secrete estrogen and progesterone
    •      the lack of progesterone causes the lining to slough off for about 5 days and then a new proliferative phase begins.
    •      if the ovum is fertilized, the developing placenta begins to secrete human chorionic gonadotropin (hCG) preventing the corpus luteum from degenerating, allowing it to continue secreting progesterone
    •      before the end of the first trimester of pregnancy, the placenta begins to secrete estrogen and progesterone and the corpus luteum degenerates and these hormones are secreted at continuously increasing levels throughout the pregnancy
  485. Follicle-stimulating hormone (FSH) is secreted by:
    A. the follicular cells.
    B. the ovaries.
    C. the hypothalamus.
    D. the anterior pituitary gland.
    D. Follicle-stimulating hormone (FSH) is secreted by the anterior pituitary gland. Together with luteinizing hormone (LH), also secreted by the anterior pituitary, FSH stimulates follicular development, ultimately producing an ovum.
    (this multiple choice question has been scrambled)
  486. The luteal surge causes:
    A. sudden shedding of the uterine lining.
    B. release of the ovum into the oviduct.
    C. the second meiotic division of a secondary oocyte.
    D. implantation of a fertilized ovum in the uterus.
    B. The phrase luteal surge refers to a sudden increase in the secretion of luteinizing hormone (LH) from the anterior pituitary; this event is associated with the release of an ovum (a haploid cell produced by the first meiotic division of the primary oocyte) into the oviduct (the fallopian tube).
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  487. Which of the following correctly characterizes the corpus luteum?
    A. It undergoes meiosis.
    B.  It is located in the uterine lining.
    C. It is nonsecretory.
    D. It secretes estrogen and progesterone.
    D. is correct. The corpus luteum is the remnant of the ruptured follicle left in the ovary after ovulation occurs. Its cells secrete estrogen and progesterone. The secretion of progesterone promotes growth of the uterus and prepares it for implantation of a zygote.
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  488. Name the hormones that control the female menstrual cycle, and describe their functions.
    FSH and LH are peptide hormones secreted from the anterior pituitary during the follicular phase to cause follicular development in the ovary. A surge of LH  causes ovulation.

    Estrogen is secreted by the follicular cells during the follicular phase and promotes proliferation of the endometrium.

    Estrogen and progesterone are secreted from the corpus luteum during the luteal phase. They cause further development of the endometrium, in preparation for zygote implantation.

    Human chorionic gonadotropin (hCG) is secreted from the developing placenta upon fertilization and implantation. It stimulates the corpus luteum to continue progesterone and estrogen secretion. In the absence of implantation and the consequent absence of placental hCG, the corpus luteum degenerates, and its hormonal secretion terminates. Without progesterone, the endometrial lining deteriorates. Menstrual bleeding follows. Also, in response to the post-luteal fall in circulating levels of estrogen and progesterone, FSH production rises, initiating a new proliferative phase.
  489. Each testis contains specialized reproductive organs. What are they called and what do they contain?

    What do the interstitial cells, situated among the twisted reproductive organs within the testes, secrete, and what stimulates this production? Give the function of this hormone.
    • seminiferous tubules
    • spermatogonia, the precursors of spermatozoa formation
    • testosterone
    • stimulated by pituitary LH (also called interstitial cell stimulating hormone, ICSH, in mature males)
    • --predominately male hormone, does not become plentiful until puberty, secreted into the bloodstream and comes into contact with all parts of the body --
    • It's principle role is to promote spermatogenesis, the division of the spermatogonia within the seminiferous tubules to produce haploid spermatozoa. It also promotes the development of secondary sex characteristics including deepening of the voice, growth of facial, axillary, and pubic hair, and enlargement of the penis and scrotum
  490. Which of the following would most likely result from impaired secretion of testosterone in the mature male?
    A. Degeneration of the testes
    B. Sudden and pronounced feminization
    C. Increased metabolic rate
    D. Absence of the gamete production
    D. is correct. Testosterone promotes spermatogenesis in the seminiferous tubules, leading to production of spermatozoa, or the male gametes. If testosterone secretion is impaired, the gametes will not be produced. Sudden and pronounced feminization does not accompany impaired testosterone secretion in a mature male. A degree of feminization may be achieved in the mature male by exogenous administration of female sex hormones.) The testes do not degenerate in the absence of testosterone. The metabolic rate bears no direct connection to testosterone secretion.
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  491. What is the hypothalamus? What do the hormones released by it control? It provides neural input and central control of what? What does it serve as a high-level coordinating and regulating center for?
    • The hypothalamus is a portion of the diencephalon of the forebrain.
    • It releases several hormones that control secretions from the pituitary gland.
    • I provides neural input and central control of the endocrine glands outside of the brain.
    • It serves as a high-level coordinating and regulating center for both the endocrine system and the autonomic nervous system.
    • It integrates a variety of information from the cerebral cortex and limbic system, and regulates output from the pituitary glands.
  492. Where is the pituitary gland located?
    It is a small structure on the underside of the brain; like the hypothalamus, it is part of the diencephalon of the forebrain. It has two halves: the anterior pituitary and the posterior pituitary.
  493. The anterior pituitary secretes six peptide hormones. Four of them play a key role in controlling other endocrine secretions; these tropic hormones act as chemical switches, stimulating or inhibiting other endocrine glands. In addition to hormones that regulate the release of other hormones at a distant gland, the anterior pituitary secretes two other hormones that interact directly with certain target organs.
     Give these six hormones and their role.
    • 1. Thyroid-stimulating hormone (TSH): stimulates the thyroid gland to secrete thyroid hormone.
    • 2. Adrenocorticotropic hormone (ACTH): stimulates the adrenal cortex to secrete cortisol.
    • 3. Luteinizing Hormone (LH): stimulates the gonads (ovaries or testes) to promote sex hormone secretion and gamete production.
    • 4. Follicle Stimulating Hormone (FSH): stimulates the gonads (ovaries or testes) to promote sex hormone secretion and gamete production.
    • 5. Growth hormone (GH): influences the development of skeletal muscle, bone, and organs in infants and children. Without growth hormone, children fail to develop normally. GH is also known as somatotropin (STH).
    • 6. Prolactin: directly targets the female breasts, where it stimulates breast development and milk production.
  494. The posterior pituitary secretes two peptide hormones. These hormones are not synthesized in the posterior pituitary; they are made in neural soma in the hypothalamus and transported via vesicles down axons to the posterior pituitary. They are stored in the posterior pituitary, from which they are released directly into the bloodstream as needed. Give the two hormones secreted by the posterior pituitary.
    • 1. Antidiuretic hormone (ADH): Discussed previously, in connection with the kidney. It is also known as vasopressin.
    • 2. Oxytocin: Released at childbirth (parturition), causing the uterus to contract and push the fetus through the birth canal.
  495. Which of the following would most likely be observed in a patient who secretes excessive quantities of thyroid hormone?
    A. Decreased cellular uptake of oxygen
    B. Decreased cellular uptake of glucose
    C. Increased cellular production of carbon dioxide and water
    D. Increased blood pH
    C. is correct. Thyroid hormone acts to increase metabolic rate -- to increase the rate at which cells burn fuel. The patient who secretes excessive quantities of thyroid hormone is hypermetabolic, burning fuel at a greater rate than normal. The burning of fuel produces carbon dioxide and water, since in aerobic respiration, oxygen serves as the ultimate oxidizing agent (electron acceptor). The increased metabolic rate would likely be associated with an increase--not a decrease--in uptake of oxygen and glucose. Hyperthyroidism does not ordinarily affect blood pH. Any tendency it might have to do so, however, would bring about a decrease, not an increase, in pH. The increased production of carbon dioxide would promote increased formation of carbonic acid, which, on dissociation, reduces pH (increases hydrogen ion concentration).
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  496. A tumor that secretes aldosterone would most likely lead to:
    A.  an increased urinary output.
    B. a decreased metabolic rate.
    C. an increased concentration of potassium in the blood.
    D. an increased concentration of potassium in the urine.
    D. is correct. Tumors commonly secrete hormones--often in an unpredictable and uncontrollable fashion. These hormones produce effects normally associated with the particular hormones. Aldosterone promotes and exchange of sodium and potassium ions between the distal tubular filtrate and the surrounding interstitium: Potassium moves into the tubular filtrate, to be excreted in the urine, and sodium moves out of the tubule, producing increased sodium concentration in the interstitium and a relative increase in the amount of water reabsorbed from the tubules. Aldosterone (a) increases urinary potassium concentration, (b) decreases extracellular potassium concentration, (c) decreases urinary sodium concentration, (d) increases extracellular sodium concentration, (e) decreases the volume of urine, and (f) increases body fluid volume.
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  497. A decrease in parathyroid hormone secretion will lead to:
    A. a decreased calcium concentration in the blood.
    B. an increased sodium concentration in the blood.
    C. a decreased metabolic rate.
    D. depletion of bone.
    A. is correct. Parathyroid hormone increased calcium concentration in the blood by promoting (a) resorption of bone (which releases calcium into the blood), (b) calcium absorption in the digestive tract, and (c) calcium reabsorption in the kidney. A deficiency of parathyroid hormone will lead to a decreased calcium concentration in the blood.
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  498. The adrenal medulla releases:
    A. aldosterone.
    B. glucocorticoids, mineralocorticoids, anabolic hormones, and sex hormones.
    C. epinephrine and norepinephrine.
    D. insulin and glucagon.
    C. is correct. Functionally, the adrenal medulla and the adrenal cortex are two separate endocrine glands; anatomically they are adjoined. The cortex (not the medulla) secretes corticosteroids, with include the mineralocorticoids (aldosterone, for example), the glucocorticoids (cortisol, for example), the anabolic hormones, and the sex hormones. The adrenal medulla releases epinephrine (adrenaline) and norepinephrine (noradrenaline). Insulin and glucagon and secreted by the pancreas, not the adrenal gland.
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  499. Hormone release is controlled via three mechanisms. List these mechanisms.
    • 1. The hypothalamus and the pituitary glad (both anterior and posterior) are the higher regulatory organs of the endocrine system; many of the hormones they secrete control other endocrine glands. Therefore, many functions of the endocrine system depend on instructions from the brain.
    • 2. Hormones can regulate other hormones and many endocrine secretions are part of a pathway that is master regulated. Hormones that control the release of other hormones are called tropic hormones.
    •      Examples:
    • organ:
    •       tropic hormone
    •            controlled hormone
    • hypothalamus:
    •       corticotropin-releasing hormone (CRH) 
    •             cortisol release
    •       thyrotropin-releasing hormone (TRH)
    •             thyroid hormone levels
    •       gonadotropin-releasing hormone (GnRH)
    •             sex hormones 
    •                (androgens, 
    •                estrogens, 
    •                and progesterone)
    • anterior pituitary:
    •       adrenocorticotropic hormone (ACTH)
    •             cortisol release
    •       thyroid-stimulating hormone (TSH)
    •             thyroid hormone levels
    •       gonadotropins
    •          (luteinizing hormone (LH) and
    •          follicle stimulating hormone (FSH)
    •             sex hormones
    •                (androgens,
    •                estrogens,
    •                and progesterone)
    • 3. hormone levels are controlled by feedback regulation, especially negative feedback.
    •      A. A change in physiological status in response to a hormone can feed back to the endocrine gland to stop hormone secretion.
    •      B. Hormones can cause feedback regulation to the higher regulatory organs (hypothalamus and pituitary gland) that are controlling their release.
  500. The hypothalamus affects secretion of corticosteroids by releasing:
    A. enzymes that catalyze secretory reactions in the adrenal cortex.
    B. thyroid-releasing hormone.
    C. catecholamines.
    D. corticotropin-releasing hormone (CRH)
    D. is correct. Corticosteroids are released from the adrenal cortex, which is stimulated by adrenocorticotropic hormone (ACTH) released from the anterior pituitary. The anterior pituitary released ACTH in response to the release of CRH from the hypothalamus.
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  501. What is a neuron?
    It is a nerve cell; the fundamental cellular unit of the nervous system.
  502. In addition to the organelles normally found in eukaryotic cells, the neuron contains a number of unique organelles specialized for the transmission of electrical impulses. List these unique organelles and their purpose.
    • Dendrites: cytoplasmic extensions of the cell that act like antenna, or sensors: they receive stimuli.
    • Axon: nerve fiber that is a single, elongated cytoplasmic extension that transmits signals.
    •      Synaptic terminals: the distal end of the axon bears these small extensions
    •         Synaptic vesicles: contained within synaptic terminals
    •            Neurotransmitters: contained within the synaptic vesicles, these molecules transmit chemical signals from one neuron to the next. In some situations, a neurotransmitter will exert and excitatory effect on a neuron, while in other, it will have an inhibitory effect.
  503. If two neurons communicate in series, then the signal from one neuron reaches the other neuron via:
    A. release of a chemical by the first neuron and its receipt by the second neuron.
    B. direct contact between axons of the first neuron and dendrites of the second neuron.
    C. direct contact between each neuron and an interneuron.
    D. direct contact between synaptic terminals.
    A. is correct. One neuron relays its message to the next by releasing a chemical messenger, called a neurotransmitter, from synaptic vesicles. Direct contact is not a means of communication between two neurons. Rather, the neurotransmitter is released from the axon's synaptic terminal into the synaptic space, and binds to receptors on the plasma membrane of the second neuron.
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  504. A resting neuron may have which of the following electrical potentials (in millivolts) across its membrane?
    A. -70 mV
    B. 0 mV
    C. +20 mV
    D. +50 mV
    A. is correct. The relative excess of positive charges outside the cell compared to the inside (as a result of the action of the sodium-potassium pump) gives rise to a negative electrical potential across the membrane (as measured from the inside of the cell).
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  505. Which of the following correctly characterizes a neuron's resting potential?
    A. It is attributable to a transmembrane calcium imbalance.
    B. It is maintained by an ATP-dependent mechanism.
    C. It creates a relative negative charge outside the neuronal membrane.
    D. It is maintained by passive diffusion.
    B. is correct. The neuron's resting potential is maintained by an uneven distribution of the cations across the membrane. The uneven distribution is not a stable situation, since passive diffusion tends to eliminate electrical and chemical gradients. Rather, the cell must expend energy to maintain it, which requires ATP. This is an example of primary active transport.
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  506. When a neuron is in its resting, unexcited state, its membrane is largely impermeable to sodium and somewhat permeable to potassium due to the presence of what?
    potassium leak channels
  507. What are the voltage-gated sodium channels?
    They are membrane channels, composed of a protein complex, that open when sodium ions, that are positively charged, move through the membrane into the interior after some electrical, chemical, or mechanical event causes the dendritic membrane to increase its sodium permeability. Once open, sodium ions flood the cell and alter the membrane potential from -70mV to +35mV which constitutes the first part of an action potential.
  508. What are voltage-gated potassium channels?
    At the peak of an action potential (when the cell potential is +35mV), the voltage-gated sodium channels become inactivated. At just about the same time (or just before), voltage-gated potassium channels open up. With the potassium channels open, potassium ions rush out of the cell along their concentration gradient, leaving the electrical potential of the cell reduced allowing the cell's interior to once again become negative and be repolarized. (Though, because the voltage-gated potassium channels stay open a little too long, too many potassium ions flow out of the cell and the potential drops to approximately -90mV and is hyperpolarized.)
  509. What is the absolute refractory period?
    At the peak of its action potential, when the cell is fully depolarized, the neuron is wholly unsusceptible to additional stimulation. This continues as the cell is repolarizing. This is called the absolute refractory period and arises because so m any of the neuron's sodium channels are inactivated and cannot reopen until the are reset.
  510. What is the relative refractory period?
    Just after the cell passes the -70mV threshold and is hyperpolarized due to the delay of the voltage-gated potassium channels, the cell is susceptible to another action potential but requires a stimulus stronger than the one normally needed by a resting cell. This phenomenon, called the relative refractory period, arises because the potential of the cell is below that of a resting cell.
  511. Depolarization of the neuron starts with:
    A. a change in the neuronal membrane's potassium permeability.
    B. active pumping of sodium inward across the neuronal cell membrane.
    C. a change in the neuronal membrane's sodium permeability.
    D. a change in the neuronal membrane's calcium permeability.
    C. is correct. Depolarization begins when voltage-gated sodium channels open, allowing sodium to rush into the cell down its gradient.
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  512. Repolarization of the neuron is caused by:
    A. a change in the neuronal membrane's potassium permeability.
    B. a change in the neuronal membrane's calcium permeability.
    C. active pumping of sodium inward across the neuronal cell membrane.
    D. a change in the neuronal membrane's sodium permeability.
    A. is correct. Repolarization occurs when potassium voltage-gated potassium channels open in response to the change in membrane potential caused by sodium influx. The loss of positive charge from the interior of the cell reestablishes the resting membrane potential.
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  513. What encases long, discrete sections of the axons of neurons in the peripheral nervous system by wrapping layers of their plasma membranes around the axon and what is this creating?
    Schwann cells (oligodendrocytes perform a similar function in the central nervous system). This creates myelin sheaths.
  514. What are the small areas of the axon that remain unmyelinated at regular intervals along the axon's length called?
    nodes of Ranvier
  515. What is the purpose of the nodes of Ranvier?
    Nodes of Ranvier are the only sites available for electrical propagation along the axon. Myelin insulation significantly accelerates the transmission of the impulse as depolarization jumps from one node of Ranvier to the next (salutatory conduction), effectively skipping across the long, insulated portions of the axon.
  516. Nodes of Ranvier are:
    A. sections of axon that contain a double membrane.
    B. exposed areas of axon that permit saltatory conduction.
    C. insulated regions of the myelinated axon.
    D. segments of axon that are encased in Schwann cells.
    B. is correct. The insulating properties of the myelin sheaths allow the nerve impulse to jump from one exposed node of Ranvier to the next, permitting more efficient and rapid propagation of the impulse.
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  517. The myelin sheath is composed of:
    A. interneurons.
    B. a high molecular weight salt.
    C. the plasma membranes of Schwann cells.
    D. a low molecular weight salt.
    C. is correct. The myelin sheath of the neurons in the PNS is composed of multiple wrapped layers of Schwann cells. It facilitates salutatory conduction, wherein an impulse jumps from one node of Ranvier to the next. The propagation along a myelinated neuron is much faster than that along an unmyelinated neuron.
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  518. What happens when the action potential impulse arrives at the end of the axon?
    It triggers voltage-gates calcium channels to open; Ca2+ flows into the cell, binds with regulatory proteins and causes exocytosis of neurotransmitter-containing synaptic vesicles: The vesicles fuse with the plasma membrane and neurotransmitter molecules are released from the cell.
  519. What is the neuron that releases the neurotransmitter called?
    The neurotransmitters are released from the terminal end of the axonal membrane called? What is the synaptic cleft and the postsynaptic membrane?
    • presynaptic neuron
    • presynaptic membrane
    • synaptic cleft - the place into which the neurotransmitters are released from the synaptic vesicles to the postsynaptic membrane
    • postsynaptic membrane - The part of the cell membrane of a neuron or muscle fiber with which an axon terminal forms a synapse.
  520. Describe the receptors on the plasma membrane of the postsynaptic cell.
    • They are specific to the neurotransmitter.
    • Each postsynaptic neuron can receive signals from  many presynaptic neurons (they express receptors for many types of neurotransmitters).
    • Note: Each neuron will release only ONE type of neurotransmitter from its presynaptic axon terminus.
  521. The nervous system contains more than 30 different chemicals that act as neurotransmitters. Give two of them.
    • 1. Acetylcholine: triggers muscle contraction and is degraded by the enzyme acetylcholinesterase.
    • 2. Epinephrine: (aka adrenaline) increases heart rate and blood pressure and decreases metabolic activity, such as that of the smooth muscle of the digestive system. It is oxidized and methylated to inactive metabolites by monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT), respectively.
  522. Which of the following statements does NOT accurately describe events associated with neural impulse?
    A. Voltage-gated channels for potassium open during repolarization, permitting efflux of potassium from the neuron.
    B. Voltage-gated channels for potassium open in the course of an action potential, permitting influx of potassium into the neuron.
    C. Both ligand-gated channels and voltage-gated channels are required for successful transmission of a nerve impulse from one neuron to the next.
    D. Ligand-gated channels open upon binding of postsynaptic receptors with the appropriate neurotransmitter.
    B. is correct. Voltage-gated sodium channels open during an action potential to allow influx of sodium ions down their concentration gradient. Each of the remaining options is an accurate statement of events occurring during neural transmission.
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  523. Acetylcholine serves as neurotransmitter at autonomic ganglia. What is the effect of acetylcholine on the postsynaptic membrane?
    A. It induces the production of synaptic knobs.
    B. It induces the production of synaptic vesicles.
    C. It induces a change that ultimately renders the postsynaptic neuron more permeable to sodium.
    D. It renders the neuron more permeable to epinephrine and norepinephrine.
    C. is correct. When a neurotransmitter (like acetylcholine) crosses the synaptic cleft and reaches the postsynaptic neuron, it can initiate depolarization of the postsynaptic neuron (unless its stimulus is subthreshold). As a result, the postsynaptic neuron increases its permeability to sodium.
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  524. Which of the following would explain the failure of a neurotransmitter to elicit and action potential in a postsynaptic neuron?
    A. The postsynaptic neuron is an interneuron.
    B. The neurotransmitter produces a subthreshold response.
    C. The postsynaptic neuron has receptors specific to the neurotransmitter.
    D. The postsynaptic neuron has been facilitated.
    B. is correct. Neuronal response to a stimulus is all or none. If a stimulus fails to reach a threshold, the neuron will not fire. Inadequate quantities of neurotransmitter or the prior inhibition of the neuron may prevent neurotransmitter from initiating depolarization. Facilitation of the neuron would tend to reduce the stimulus necessary to bring about depolarization. That the postsynaptic neuron should be an interneuron does not affect the dynamics just described. Interneurons, like other types of neurons, respond to stimuli in an all-or-none fashion.
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  525. The human nervous system is comprised of two principal divisions. What are they?
    • Central nervous system (CNS)
    • Peripheral nervous system (PNS)
  526. Fill out the divisions and subdivisions of the nervous system:
                      The Nervous System
                     ↙                          ↘
           Peripheral                        Central
                ↙↘                              ↙          ↘
     ______   Autonomic     _____ ___*  ____*
                   ↙      ↘          
    __________    ____________*
    •                  The Nervous System
    •                  ↙                          ↘
    •        Peripheral                        Central
    •             ↙↘                           ↙          ↘
    •  Somatic   Autonomic     Spinal cord*  Brain*
    •                ↙      ↘          
    • Sympathetic     Parasympathetic*

    • ♦ Spinal cord: white matter, gray matter
    • ♦ Brain: cerebral cortex, hypothalamus, thalamus, pons, cerebellum, medulla
    • ♦ Parasympathetic nervous system: vagus nerve
  527. When humans register a stimulus (whether consciously or not), information is sent to the CNS, where it is processed, and then from the CNS back to the site of the body that responds to the stimulus. This requires the interaction of several different types of neurons and cells. List these.
    • 1. Sensory receptor cells: register a given stimulus, such as smell or sound, and gather information.
    • 2. Sensory neurons (aka afferent neurons): receive information from the sensory receptors and send it to the central nervous system; in some cases (such as olfactory transduction), the receptor is a modified part of the sensory neuron itself.
    • 3. Interneurons (aka associative neurons): In the CNS, one or more interneurons receive and process the information and generally function in relaying signals from neuron to neuron.
    • 4. Motor neurons (aka effector or efferent neurons): transmit nerve impulses from the CNS to the target muscle, organ, or gland.
    • **Afferent nerves transmit nerve impulses to the CNS and efferent nerves conduct impulses from the CNS to the muscles or glands.
  528. During embryonic development, what gives rise to the brain, and the spinal cord?
    • Brain: the anterior section of the neural tube
    • Spinal cord: the posterior portion of the neural tube
  529. What are the brain and the spinal cord are protected by?
    • 1. layers of connective tissue (the meninges)
    • 2. bone (the spine and the skull)
    • 3. circulating cerebrospinal fluid (CSF) that acts as a liquid shock absorber
  530. What are the embryonic precursors of the adult brain structures and what do they become?
    • hindbrain: cerebellum, the pons, the medulla
    • midbrain: structures that govern visual auditory reflexes and coordinate information of posture and muscle tone
    • forebrain: the diencephalon (includes the thalamus, the hypothalamus, and the pituitary gland) and the telencephalon (includes the cerebrum, the limbic system and the basal nuclei)
  531. Describe the cerebrum.
    • ♦Composed of two hemispheres
    •    ♢Divided by a longitudinal fissure
    •    ♢Connected by the corpus callosum
    •       -a thick bundle of axons
    • ♦The largest portion of the human brain
    • ♦Cerebral cortex
    •    ♢Gray matter overlying the cerebrum
    •       -contains neuronal cell bodies (or soma)
    •         that conduct the highest of intellectual
    •         functions
    •    ♢Governs voluntary motor activity, functions
    •       of language and cognition
    •    ♢Divided into four pairs of lobes
    •       -frontal
    •       -parietal
    •       -temporal
    •       -occipital
  532. Give the subdivision (if applicable) and the function of each:
    Spinal cord
    • Spinal cord:
    •   ♢no subdivision
    •   ♦simple spinal reflexes
    •   ♦control of primitive processes
    • Medulla:
    •   ♢Hindbrain
    •   ♦controls autonomic processes (bp, heartbeat,
    •     respiratory rate, vomiting)
    • Pons:
    •   ♢Hindbrain
    •   ♦some autonomic control
    •   ♦controls anti-gravity posture and balance
    • Cerebellum:
    •   ♢Hindbrain
    •   ♦integrating center
    •   ♦coordination of complex movement, balance,
    •    and posture
  533. Give the subdivision (if applicable) and the function of each:
    • Midbrain:
    •   ♢no subdivision
    •   ♦integration of visual and auditory info
    •   ♦wakefulness
    • Thalamus:
    •   ♢Forebrain diencephalon
    •   ♦somatic/conscious sensation
    • Hypothalamus:
    •   ♢Forebrain diencephalon
    •   ♦homeostasis (ex. temperature)
    •   ♦primitive emotions (ex. hunger, rage..)
    • Pituitary:
    •   ♢Forebrain diencephalon
    •   ♦homeostasis via hormone release
    •   ♦controlled by the hypothalamus
    •   ♦2 peptide hormones from posterior pituitary
    •   ♦6 peptide hormones from anterior pituitary
  534. Give the subdivision (if applicable) and the function of each:
    Basal nuclei
    Limbic System
    Cerebral cortex (in general)
    Frontal lobes
    • Basal nuclei:
    •   ♢Forebrain telencephalon
    •   ♦regulate body movement
    • Limbic System:
    •   ♢Forebrain telencephalon
    •   ♦emotion
    • Cerebral cortex (in general)
    •   ♢Forebrain telencephalon
    •   ♦intelligence, communication, memory,
    •    planning, reading, voluntary movement..
    •   ♦left side controls speech and motor function
    •    on the right side of body
    •   ♦right side controls visual spatial reasoning
    •    and music, and left side motor function
    • Frontal lobes:
    •   ♢Forebrain telencephalon
    •   ♦voluntary movement
    •   ♦complex reasoning skills
    •   ♦problem solving
  535. Give the subdivision (if applicable) and the function of each:
    Parietal lobes
    Temporal loves
    Occipital lobes
    Corpus callosum
    • Parietal lobes:
    •   ♢Forebrain telencephalon
    •   ♦general sensation (ex. touch, temperature..)
    •   ♦gustation (taste)
    • Temporal lobes:
    •   ♢Forebrain telencephalon
    •   ♦auditory and olfactory sensation
    •   ♦short-term memory
    • Occipital lobes:
    •   ♢Forebrain telencephalon
    •   ♦visual sensation and processing
    • Corpus callosum
    •   ♢no subdivision
    •   ♦connects the left and right cerebral
    •    hemispheres
  536. A patient who shows loss of balance and the inability to perform tasks that call for rapid and refined coordination of musculature most likely suffers from dysfunction at which of the following sites:
    A. Cerebellum
    B. Corpus callosum
    C. Medulla
    D. Hypothalamus
    A. is correct. The cerebellum controls such functions as balance and the ability to perform tasks that call for rapid and refined coordination and musculature. (Sewing and piano playing are examples of such activities).
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  537. A patient who shows loss of ability to think abstractly most likely has a lesion affecting the:
    A. spinal cord.
    B. hypothalamus.
    C. cerebral cortex.
    D. thalamus.
    C. is correct. The processes of abstract thought are most closely associated with the cerebral cortex. A grossly observable loss in that regard is almost certainly associated with a lesion of the cerebral cortex.
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  538. In humans, appetite and body temperature are controlled by the:
    A. medulla.
    B. cerebellum.
    C. hypothalamus.
    D. cerebrum.
    C. is correct. The hypothalamus maintains homeostasis, adjusting body temperature, fluid balance, and appetite. It governs autonomic functions and links the endocrine and nervous systems. The cerebellum governs posture, muscle tone, and equilibrium. The cerebrum controls complex integrative processes, such as learning, memory, and reasoning. The medulla regulates blood pressure, heart beat, and respiration, and controls reflex activity, such as sneezing.
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  539. What does the spinal cord govern? What does the interior and exterior of the spinal cord contain?
    • Simple motor reflexes
    • Interior: gray matter (composed of cell bodies of spinal cord neurons)
    • Exterior: composed of white matter (or myelinated spinal cord axons) -- so called for the pale appearance of myelin which insulates the axon
  540. Gray matter refers to:
    A. neuronal cell bodies within the central nervous system.
    B. the substance of the cerebral cortex.
    C. neuronal axons within the central nervous system.
    D. the substance of the spinal cord.
    A. is correct. As it happens, the cell bodies of most neurons within the central nervous system have a grayish appearance on gross inspection. Within the brain and the spinal cord alike, the gray matter generally refers to the cell bodies of the enormous numbers of neurons that are situated there. White matter refers to the myelinated axons of these neurons.
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  541. Cite the components involved in the Achilles reflex and describe their respective functions.
    A simple reflex arc is a monosynaptic reflex requiring sensory receptors, a sensory neuron, and a motor neuron. Tapping on a muscle's tendon with a mallet will cause its fibers to stretch. The stretch of the fibers is registered by sensory neuron stretch receptors located on the muscle. The neuron transmits the stretch signal to the central nervous system (spinal cord), where it synapses with a motor neuron. The motor neuron then transmits its signal back tot he muscle, releasing acetylcholine at the neuromuscular junction.
  542. Which of the following is not normally a component of a simple reflex arc?
    A. An afferent neuron
    B. An efferent neuron
    C. The peripheral nervous system
    D. An interneuron
    D. is correct. A simple reflex arc involves one afferent neuron (with specialized receptors at its dendritic end), and one efferent neuron, which synapses with the afferent neuron in the spinal cord. It does not involve any interneurons (or associative neurons). Since the important parts of this pathway lie outside the brain and spinal cord, the simple reflex arc is said to belong to the peripheral nervous system.
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  543. The peripheral nervous system (PNS) conveys information to and from the central nervous system (CNS). What two systems is it divided into?
    • Somatic nervous system
    • Autonomic nervous system
  544. What do the afferent neurons and efferent neurons perform in the somatic nervous system?
    • Afferent: receive information from sensory receptors for pain, touch, temperature and proprioception
    • Efferent: innervate skeletal muscle by releasing the neurotransmitter acetylcholine
    • **The somatic nervous system governs voluntary activities that we can consciously control.
  545. The autonomic nervous system controls involuntary actions, such as those of the digestive, respiratory, circulatory and excretory systems. What are the two subdivisions of the autonomic nervous system?
    • parasympathetic nervous system
    • sympathetic nervous system
  546. In the autonomic nervous system, there are two efferent (or motor) neurons that work together to send instructions from the CNS to the organs, glands, and muscle (cardiac and smooth only) of the body. List them and give a simple description of their interaction.
    • The preganglionic neuron has its cell body in the brainstem or the spinal cord. It synapses with the postganglionic neuron and releases acetylcholine. The postganglionic neuron can release acetylcholine or norepinephrine to control the effector tissue.
    • Note that a ganglion is a cluster of nerve cell bodies in the PNS.
  547. What are examples of the vegetative functions that the sympathetic nervous system inhibits when activated?
    gastrointestinal motility and digestive secretion
  548. What is the vagus nerve?
    • Part of the parasympathetic nervous system
    • It sends parasympathetic innervation to the thoracic and abdominal regions
    • One of the major effects of the vagus nerve innervation is slowing down the heart rate below the rate that automatically generated by the SA node.
  549. Give the sympathetic and parasympathetic information for each of the given functions:
    Heart rate
    GI tract
    Bronchial smooth muscle
    • System      Sympathetic  ||  Parasympathetic
    • General:    Fight & flight || Rest & digest
    •               Mobilize energy || store energy
    • Heart rate:     Increased || Decreased
    • Pupils:                 Dilate || Constrict
    • Vision:  Favors far vision || Favors near vision
    • GI Tract: Inhibit mobility || Stimulate mobility
    • Bladder:              Inhibit || Stimulate
    • Bronchial          Relaxed, || Constricted,
    •  smooth muscle:   open   ||  closed, shallow
  550. Give the sympathetic and parasympathetic information for each of the following structures:
    1. Origin of pre-ganglionic neuron
    2. Length of the pre-ganglionic neuron
    3. Neurotransmitter released by the pre-ganglionic ntm
    4. Length of the post-ganglionic neuron
    5. Neurotransmitter released by the post-ganglionic ntm
    • System:     Sympathetic || Parasympathetic
    • 1.     Thoracic & lumbar  || Brainstem & sacral 
    •                spinal cord     ||    spinal cord
    • 2.                        Short || Long
    • 3.             Acetylcholine || Acetylcholine
    • 4.                         Long || Short
    • 5.Norepinephrine (most) || Acetycholine
  551. Which of the following statements is false?
    A. The somatic and the autonomic nervous systems are subdivisions of the sympathetic nervous system.
    B. The peripheral and the central nervous systems constitute the two broad divisions of the nervous system.
    C. The parasympathetic and sympathetic nervous systems are subdivisions of the autonomic nervous system.
    D. The spinal cord and the brain are constituents of the central nervous system.
    A. is the false statement. The somatic and autonomic nervous systems are subdivisions of the peripheral nervous system. The other three statements characterizing the subdivisions of the nervous system are accurate.
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  552. The vagus nerve is a principal component of the parasympathetic nervous system. Excessive activity of the vagus nerve would most likely produce:
    A. failure of the stomach to secrete hydrochloric acid.
    B. abdominal cramping and diarrhea.
    C. an impaired cough and gag reflex.
    D. high heart rate and blood pressure.
    B. is correct. The parasympathetic and sympathetic nervous systems are components of the autonomic nervous system. The sympathetic system mediates the "fight or flight" response, tending to increase heart rate and blood pressure. The parasympathetic system controls such functions as coughing, gagging, digestion, and parturition. Hyperactivity of the vagus nerve would be expected to enhance motility of the digestive tract, producing abdominal cramping and diarrhea.
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  553. A given neuron emanates from the spinal cord and synapses directly with a skeletal muscle cell. Which of the following correctly characterizes the neuron?
    A. It belongs to the parasympathetic nervous system.
    B. It is an efferent neuron.
    C. It is an afferent neuron.
    D. It belongs to the sympathetic nervous system.
    B. is correct. If a neuron conducts its impulse from the central nervous system to the periphery (a skeletal muscle, for example), it is an efferent, or effector, neuron. An afferent neuron conducts its impulse toward the central nervous system. Because the neuron lies, for the most part, outside the brain and spinal cord, it is part of the peripheral nervous system, not the central nervous system. It belongs to the somatic, and not to the autonomic nervous system because it controls the movement of voluntary (skeletal) muscle. Therefore, it belongs to neither the sympathetic nor the parasympathetic system, both of which are components of the autonomic nervous system.
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  554. What are the five stimuli that humans respond to?
    tactile, olfactory, gustatory, auditory, and visual
  555. List the sensory receptor types.
    • Mechanoreceptors: responds to mechanical disturbances. These include stretch receptors, tactile receptors, proprioceptors, and auditory receptors.
    • Chemoreceptors: Responds to particular chemicals and register taste and smell
    • Thermoreceptors: stimulated by changes in temperature
    • Electromagnetic receptors: stimulated by electromagnetic waves (photoreceptors-rods and cones in the eye)
    • Nociceptors: pain receptors
  556. What two functions does the ear serve?
    • 1. maintenance of postural equilibrium
    • 2. reception of sound
  557. What are the three basic divisions of the ear?
    inner, external, and middle
  558. Where is the vestibular apparatus located?
    What is its function?
    Describe what of what it consists.
    • The inner ear
    • interprets positional information required for maintaining equilibrium
    • a membranous labyrinth situated within the three semicircular canals
  559. Describe what occurs when there is movement of the head?
    • Movement of the head causes movement of fluid within the labyrinths and displacement of specialized hair cells (the crista) located in the ampulla at the base of the semicircular canals.
    • This crista displacement initiates sensory impulses conveyed via the vestibular nerve to centers in the cerebellum, midbrain, and cerebrum, where directional movement and position are interpreted.
  560. Describe how each division of the ear is involved in the auditory system.
    • External (or outer) ear:
    •   Composed of the pinna, which funnels sound waves into the ear canal.
    • Middle ear:
    •   Sound waves cause vibrations in the tympanic membrane, setting into motion the three auditory bones-- the malleus, incus, and stapes. The stapes movement is transmitted across the oval window into the inner ear.
    • Inner ear:
    •   movement from across the oval window sets up vibrations in the fluid of the cochlea, which causes bending of auditory hair cells in the organ of Corti. The cochlear nerve and the vestibular nerve form the two branches of the acoustic nerve (8th cranial nerve).
  561. Give the path that the transmission of light through the human eye follows.
    • Light enters the cornea
    • traverses the aqueous humor
    • passes through the pupil
    • proceeds through the lens
    • and the vitreous humor
    • until it reaches the light receptors of the retina.
    • Electrical signals are then transmitted via the optic nerve to visual centers in the brain.
  562. What is myopia and what is the impact it has on the lens?
    • nearsightedness
    • the lens focuses light from a distant object in front of the retina
  563. What is hyperopia and what is the impact it has on the focusing of light?
    • farsightedness
    • light from a nearby object is focused behind the retina
  564. Describe the photoreceptors the retina uses to sense light rays.
    • located in the outer layer, both contain pigments, allowing them to absorb energy from light rays
    • rods: specialized to register dim light, rhodopsin is the rod's pigment
    • cones: specialized to register bright lights as well as color, subdivided into red-absorbing, blue-absorbing, and green-absorbing, opsin (similar to rhodopsin) mediates light reception for the cones
  565. What is the function of the iris?
    The iris, the colored part of the eye, contains muscles that dilate and constrict to regulate the amount of light that reaches the retina.
  566. What changes the shape of the lens as the eye shifts its focus from distant to nearby objects?
    The ciliary muscle
  567. What is the largest organ of the body and what is its purpose?
    • The skin
    • -maintains body temperature
    • -registers information from the environment
    • -provides a barrier against infection
  568. What are the three layers of which skin is composed?
    • the epidermis
    • the dermis
    • and the subcutaneous
  569. Describe the epidermis.
    • Composed of stratified squamous epithelium
    • Layered, flat cell structure
    • Stratum corneum (external layer)
    •      composed of many layers of dead cells containing the protein keratin
    •      waterproof and provides resistance to invasion of the body by microorganisms
    •      continuously renews itself by sloughing off cells, which are replaced by keratinized epithelial cells from deeper layers
    • Stratum germinativum (beneath the stratum corneum)
    •      where skin cells replicate through mitosis and where keratin is produced
    •      cells from the germinativum layer migrate upward to the surface, away from the capillary beds that nourish the skin. As they lose contact with capillaries, the cells die and form the layers of the corneum
  570. Describe the dermis.
    • Directly underlies the stratum germinativum of the epidermis
    • Contains the blood vessels, nerve endings, sebaceous glands (which secrete oils), and sweat glands.
    •      The sweat glands secrete water and ions in response to high temperatures and sympathetic stimulation serving to maintain a stable body temperature and optimal balance of sodium and chloride ions in the body.
  571. Describe the subcutaneous tissue.
    • Primarily adipose tissue
    • Also called hypodermis
    • A protective, insulating layer of fat, or adipose tissue
  572. For MCAT purposes, a gene is a sequence of DNA on a chromosome, which codes for a gene product. There are three gene products. List them.
    • 1) rRNA, made via transcription,
    • 2) tRNA, made via transcription,
    • 3) polypeptide, made via transcription and translation. The polypeptide for which a gene codes might represent a discrete functional protein or one subunit of a protein, which is functional when all of its subunits are fully assembled. As a general rule, one gene codes for one polypeptide, but remember there may be different forms of the polypeptide in eukaryotes due to alternative splicing. In most eukaryotic organisms, most genes code for peptides.
  573. Most DNA in a chromosome does not constitute genes: much of the DNA housed within a chromosome serves to do what?
    • regulate the function of other DNA sequences that do code directly for polypeptides
    • in eukaryotes, there are also non-protein-coding DNA sequences called introns
    • some chromosomal DNA sequences serve no (presently) known function at all
    • only about 1 percent of the DNA found on a given human chromosome directly codes for polypeptide formation -- all genes contain chromosomal DNA sequences, but not all chromosomal DNA sequences constitute genes.
  574. Finish the following statements:
    1) Genes are composed of DNA on chromosomes and can code for one of three final gene products: _________
    2) The proteins formed via transcription and translation are encoded by ______
    3) An organism's genetic traits are traceable, largely due to ___________
    • 1) Genes are composed of DNA on chromosomes and can code for one of three final gene products : rRNA, tRNA, or a polypeptide.
    • 2) The proteins formed via transcription and translation are encoded by DNA on the chromosomes.
    • 3) An organism's genetic traits are traceable, largely due to the proteins formed by its cells via the processes of transcription and translation.
  575. In biochemical terms, genes are embodied most directly and immediately in subunits of:
    A. carbohydrate.
    B. protein.
    C. nucleic acid.
    D. lipopolysaccharide.
    C. is correct. A gene is composed of units of chromosomal DNA (deoxyribonucleic acid), a nucleic acid. Via the mechanism of transcription followed by translation, genes exert their influence over cellular structure and function by directing, from their "headquarters" in the nucleus, the synthesis of proteins that serve as enzymes and structural components of the cell.
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  576. What is the area on a chromosome on which a gene is physically located?
    genetic locus; the locus of a gene is its address on the chromosome and in the genome
  577. At a given genetic locus, the two chromosomes of a given homologous pair will be:
    A. could be either identical in DNA sequence or different in DNA sequence and code for different versions of the same gene.
    B. different in DNA sequence and code for different genes.
    C. identical in DNA sequence.
    D. different in DNA sequence and code for different versions of the same gene.
    A. is correct. At any given genetic locus, the two chromosomes of a given homologous pair might be identical in DNA sequence and code for the same form of the gene, or different in DNA sequence and code for different versions of the same gene.
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  578. What are alleles?
    Different forms or versions of a gene are called alleles. Alleles can have different DNA sequences and a given gene can have numerous alleles. However, since humans are diploid, their genome can at most contain two alleles of a given single-copy gene. Some humans contain only one allele of some genes, if both their homologous chromosomes contain the same allele.
  579. What is a genotype?
    The full complement of alleles possessed by an organism represents its genotype.
  580. Among the following, "allele" is best described as representing:
    A. corresponding regions on homologous chromosomes at which variance may occur as to actual DNA composition.
    B. a segment of DNA that expresses itself only in the absence of a corresponding segment on a homologous chromosome.
    C. a length of nucleic acid that codes for a single enzyme that catalyzes the processes of transcription and translation.
    D. a genetic locus.
    A. is correct. In the somatic cells of sexually reproducing eukaryotic organisms, chromosomes exist in homologous pairs. The human nucleus, for example, harbors twenty-two pairs of autosomes and one pair of sex chromosomes, for a total of forty-six chromosomes housed within twenty-three pairs. The two members of each chromosomal pair are "homologous" but not identical. At corresponding locations (genetic loci), the two chromosomes of a homologous pair may or may not be identical. Each of the diverse (two or more) variants of DNA sequence possibly allocated to each locus constitutes an allele.
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  581. One's overall genotype refers to the:
    A. degree of identity as to the alleles carried on homologous chromosomal pairs.
    B. traits and attributes overtly manifest in his/her cellular structure and function.
    C. extent and degree to which his/her alleles create observable traits.
    D. totality of the alleles present on all his/her chromosomes.
    D. is correct. The full complement of alleles possessed by an organism represents its genotype. Alleles vary in the manner and extent to which they express themselves as observable traits, or phenotypes (which is what is described in two of the choices). Phenotype depends on the alleles of genes, but does not define it. It is also true that any given genetic locus on a pair of homologous chromosomes (or for any gene) alleles may be identical or variable. That truth, however, does not explain the meaning of "allele."
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  582. Tied to the meiotic process is the law of segregation. What does this state?
    • Recall that homologous chromosomes line up on the metaphase plate, across from each other, in meiotic metaphase I. During anaphase I, homologous pairs of chromosomes separate so that each of the two daughter takes one member of each homologous pair. For every genetic locus on every chromosome of the diploid parent cell, the gamete obtains one allele. Because the homologous chromosomes are separated into separate daughter cells at the end of meiosis I, the cell is haploid from this point onward.
    • So, the law of segregation:
    •   --every individual possess a pair of alleles for any particular trait and that each parent passes a randomly selected copy (allele) of only one of these to its offspring.
  583. Related to the law of segregation is the law of independent assortment. What does this law state?
    • It reflects the phenomenon that at anaphase I, each homologous pair separates independently to the manner in which any other homologous pair separates.
    • --separate genes for separate traits are passed independently of one another from parents to offspring.
  584. What is a phenotype?
    The ultimate significance of genotype lies in the traits it produces, meaning the features, attributes, or characteristics that it does (or does not) impart to the organism. Phenotype is the expression of alleles "traits"- what you observe.
  585. Which of the following correctly characterizes the relationship between genotype and phenotype?
    A. Genotype is a function of phenotype.
    B. Phenotype is a function of genotype.
    C. Genotype and phenotype are related in some individuals, but not in others.
    D. Genotype and phenotype are functions of one another.
    B. is correct. Phenotype is governed by genotype and genotype creates phenotype, meaning phenotype is a function of genotype. To say they are functions of one another may be tempting at first glance because so much of biology involves complex relationships among and between various factors and phenomena, each affecting the other. Nonetheless, that would be an incorrect answer. One's phenotype--his/her complement of traits--does not affect his/her genotype and it does so in all individuals.
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  586. What does the word homozygous mean?
    The essence of the word homozygous refers to an organism whose two alleles for a given locus, or gene, are identical. On the other hand, if, for some genetic locus, an organism carries two different alleles on corresponding sites of homologous chromosomes, it is said to be heterozygous. The phenomena of homozygous and heterozygous genotypes give phenotypic effect to dominant and recessive alleles.
  587. If a given individual is heterozygous at a particular gene, then at that genetic locus, the individual has:
    A. two identical alleles.
    B. one allele from one parent and no allele from the other.
    C. two different alleles.
    D. two alleles derived from a single parent.
    C. is correct. A sexually reproduced diploid organism gets one of each of its chromosomes from each of its parents. For every gene at every locus on the autosomes, one allele will be inherited from the father and one from the mother. If an organism receives two identical alleles for a given locus, it is homozygous. If an organism receives two different alleles from its parents, it is heterozygous. The option that one allele is from one parent and no allele from the other seems to be an impossible phenomenon, given that half the chromosomes come from an organism's mother and half from the father. However, it is important to note that this is possible, and refers to phenomena that occur only with respect to the sex chromosomes.
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  588. When two alleles interact in a specific way, we say that they exhibit classical dominance (or classical Mendelian dominance). What are the essential features and phenomena associated with classical dominance?
    • 1) Dominant alleles are denoted by a capital letter and recessive traits are denoted by a lower case letter.
    • 2) When an individual is either homozygous for the dominant allele (such as TT) or heterozygous (such as Tt), they express the dominant phenotype (such as T positive).
    • 3) When an individual is homozygous for the recessive allele (such as tt), they express the recessive trait (such as T negative).
  589. If, in a given population, the alternative traits of curly hair (H) and straight hair (h) exhibit classic dominance, which of the following genotypes would NOT create a phenotype for curly hair?
    A. hh
    B. Hh
    C. HH
    D. hH
    A. is correct. This answer shows a genotype that features two recessive alleles (hh) and will produce a phenotype for the recessive trait (straight hair). All other choices show genotypes that carry, on at least one chromosome, the dominant allele (H). HH depicts a genotype that is homozygous for curly hair. Choices Hh and hH depict equivalent heterozygous genotypes, both of which will create a phenotype for the dominant curly hair.
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  590. What is the Punnett square and how does it help to identify the genotypic combinations possible from a mating?
    • If two individuals of known genotype mate, a Punnett square can be drawn to show possible combinations. Consider the trait of eye color and assume that it manifests via classical dominance; the dominate B allele codes for brown eyes and the recessive b allele codes for blue eyes. If a mating occurs between a heterozygous individual and a homozygous recessive individual, the Punnett sequence would look like this:
    •       Possible gametes
    •        from Bb parent     B     b   
    • Possible gametes   b | Bb | bb |
    •  from bb parent     b | Bb | bb |
    •        B = brown eye color allele
    •        b = blue eye color allele
    • For the offspring, the Punnett square shows two possible genotypes: Bb and bb.
    • Further, it shows that in ideal statistical terms,
    •   fifty percent of offspring will have Bb genotype
    •   fifty percent of offspring will have bb genotype
    •   fifty percent of offspring will be brown-eyed
    •   fifty percent of offspring will be blue-eyed
  591. For each of the following, give the genotypic ratio of offspring and the phenotypic ratio of offspring:
    1) AA x aa
    2) AA x Aa
    3) Aa x aa
    4) Aa x Aa
    • 1) 100% Aa | 100% dominant A phenotype
    • 2) 50% AA  | 100% dominant
    •     50% Aa   |     A phenotype
    • 3) 50% Aa   | 50% dominant A phenotype
    •     50% aa   | 50% recessive a phenotype
    • 4) 25% AA  |
    •     50% Aa  | 75% dominant A phenotype
    •     25% aa   | 25% recessive a phenotype
    •       This is also called a 1:2:1 ratio
  592. Give the genotypic ratio and the phenotypic ratio of offspring for the following parental crosses.
    1) AaBb x aabb
    2) AaBb x AaBb
    • 1) Genotypic = 25% of each (AaBb, Aabb, aaBb, aabb), Phenotypic = 25% of each (A and B, A and b, a and B, a and b
    •  This cross is also called a testcross, because one of the individuals is homozygous recessive.
    • 2) Genotypic = It is too complicated to predict the genotypic ratios in a heterozygous dihybrid cross. Instead, break the cross down into the two separate genes, calculate the probabilities associated with each, and then multiply these two numbers, since you want to include the results from gene 1 and gene 2 in the final answer. Phenotypic = 9:3:3:1 ratio (9 offspring have the A and B phenotypes, 3 A and b, 3 a and B, 1 a and b)
  593. If Trait Z exhibits dominance, and one parent is heterozygous and the other is homozygous recessive, then:
    A. 100 percent of offspring will express the dominant phenotype.
    B. approximately 25 percent of offspring will express the recessive phenotype.
    C. approximately 50 percent of offspring will express the recessive phenotype.
    D. approximately 25 percent of offspring will express the dominant phenotype.
    C. is correct. The parental cross is Zz x zz (testcrossing a monohybrid heterozygote). This cross will result in 50 percent of offspring with the Z phenotype (genotype Zz) and 50 percent of offspring with the z phenotype (zz genotype). Because this is a testcross, all the offspring receive recessive alleles from the testcross parent (zz in this case). This allows both alleles of the other parent to show themselves in the offspring.
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  594. A woman heterozygous for brown eyes (blue are recessive) and brown hair (blond is recessive) mates with a man with the same genotype. What is the probability they will have a son with brown hair and brown eyes who is able to have blue-eyed children himself?
    A. 3/8
    B. 3/16
    C. 9/16
    D. 9/32
    • B. is correct. If E = brown eyes and e = blue eyes, and H = brown hair and h = blond hair, the parental cross is EeHh x EeHh. Starting with the eye color locus, if the son has brown eyes, he must have one E allele. If he is able to have glue-eyed children, he must also have one e allele. Therefore, we want to find the probability of the son being Ee given the parental cross Ee x Ee for this locus. This is 1/2.
    • Next, analyze the hair color locus. He must have an H allele to have brown hair. Since this is the only information given, the second allele could be either h or H. Given the parental crossing of Hh x Hh, the probability of the son having Hh or HH is 3/4.
    • Finally, the probability that the child will be a boy is 1/2.
    • Since the child must be male, and have brown hair, and have brown eyes (but be able to have blue-eyed children), the rules of probabilities says to multiply the three results.
    • The overall probability:
    • 1/2 x 3/4 x 1/2 = 3/16.
    • Note: if the question have asked for probability of the offspring having brown hair or brown eyes, the results would have needed to be added, not multiplied.
  595. What is incomplete dominance?
    • Alternative alleles do not always (or even usually) interact to exhibit classic dominance. For some traits, alleles interact to produce an intermediate phenotype or a blended phenotype. In this case, the trait is said to exhibit incomplete dominance.
    • For example, if flower color in plants exhibits incomplete dominance, and plants with an RR genotype have red flowers, and plants with an rr genotype have white flowers, plants with an Rr genotype would have pink flowers.
  596. What is co-dominance?
    • Two different alleles for the same locus might express themselves not as an intermediate phenotype, but as two distinct phenotypes both present in a single individual. Alleles for the human blood groups (which determine your blood type) exhibit this form of interaction, known as co-dominance.
    • Human blood is commonly typed as A, B or O, and either positive or negative. Blood type is determined by the expression of antigens on the surface of red blood cells (also called erythrocytes). An antigen is a molecule that is recognized by an antibody.
    • The blood group (A, B, AB or O) is governed by three alleles designated IA, IB, and i at one locus, (1) the IA allele codes for an enzyme that adds the sugar galactosamine to the lipids on the surface of red blood. People with this allele express antigen A on their erythrocytes, (2) the IB allele codes for an enzyme that adds the sugar galactose to the lipids on the surface of red blood cells. People with this allele express antigen B on their erythrocytes, and (3) the i allele codes for a protein that does not add any sugar to the surface of red blood cells.
    • An individual of genotype (1) IAIA or IAi shows the addition of galactosamine to the surface lipids of the red blood cells (or expresses antigen A); this person has blood type A, (2) IBIB or IBi shows the addition of galactose to the surface lipids of the red blood cells (or expresses antigen B); this person has blood type B, (3) IAIB shows the addition of both galactose and galactosamine to the surface lipids of the red blood cells (or expresses both antigens A and B); this person has blood type AB, and (4) ii shows the addition of no sugar to the surface lipids of the red blood cells (expresses neither antigen A nor antigen B); this person has type O blood.
    • Note: the alleles IA and IB exhibit co-dominance. The individual who carries both alleles exhibits the trait tied to each. Neither allele is recessive in relation to the other. At the same time, however, the i allele, which does not code for the addition of any sugar on the red blood cell surface, is recessive in relation to both the IA and IB alleles. Only the genotype ii produces that phenotype.
    • Positive or negative blood type is determined by a separate gene called the Rh factor or antigen, which exhibits classical dominance. If an individual expresses antigen D, they have positive blood. If they do not express antigen D, they have negative blood.
  597. If an individual has blood type A, it can be concluded that:
    A. he carries at least one i allele.
    B. his genotype at the relevant locus is IAIA.
    C. his genotype at the relevant locus is IAi.
    D. he carries either one or two IA alleles.
    D. is correct. The trait for human blood type (A, B, or O) exhibits co-dominance. Among the three alleles extant within the population (IA, IB, and i), any one individual carries two (since humans are diploid organisms). Blood type A can be due to one of two genotypes, either IAIA or IAi. While the other choices are possible for an individual with blood type A, they are not guaranteed.
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  598. What are the two mechanisms under which genes generally are altered?
    • recombination
    • mutation
  599. What is genetic recombination?
    • A process in which genetic information on one chromosome is moved to a
    • chromosome that belongs to some other cell, or a
    • different chromosome within the same cell (often a homologous chromosome.)
    • Example: The human immunodeficiency virus (HIV) transfers a segment of its genome to a human chromosome, and the human cell thereby undergoes (severely pathologic) genetic recombination.
  600. What is the process of crossing over?
    • An instance of genetic recombination
    • During the synapsis phase of the first meiotic division, homologous chromosomes joined on the spindle apparatus undergo breakage and an exchange of genetic information. A physical "piece" breaks from each chromosome of the pair and "crosses over" to become integrated into its counterpart.
  601. What is mutation?
    • Mutation refers to the actual alteration of the DNA sequence on the chromosome.
    • Often mutation produces effects deleterious to the organism's function, adaptability, and survival. Much more rarely, it leads to improvement in the organism's adaptability. In some cases, mutation confers on the organism neither an advantage nor a disadvantage.
  602. Mutation of what cells is said to be critical to the genetic variability that underlies evolution and natural selection?
    Mutation of germ-line cells (mutation of a somatic cell is less significant to the evolutionary process but may have serious consequences for the affected individual)
  603. There are two common types of mutations. What are they?
    • point mutation: when one nucleotide unit is substituted for another
    • frameshift mutation: when one or more nucleotides are added or deleted (note that the addition or deletion of a multiple of three nucleotides does not cause a frameshift mutation)
  604. Which of the following, if it occurs in a young human adult of reproductive age, is LEAST likely to contribute to the process of evolution?
    A. Spontaneous mutation in a spermatogonia
    B. Damage to a somatic cell
    C. Mutagenic ultraviolet exposure to a ootid
    D. Crossing over
    B. is correct. Critical to the process of evolution is the phenomenon of genetic alteration and variation that affects offspring. Damage to a somatic (non-gamete-producing) cell may affect the individual who suffers the mutation, but it will not normally affect the genetic constitution of his or her offspring.
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  605. A point mutation that changes a codon but that particular change does not affect the amino acid that is added during translation and therefore would not affect gene function is termed what? And if the changed codon does affect the amino acid that is added during translation? And if the mutation causes the conversion of an mRNA codon to a stop codon?
    • silent mutation
    • missense mutation (missense mutation tend to be more serious if the occur at an important location of the protein, such as the active site of an enzyme)
    • nonsense mutation
  606. Refer to the genetic code. If a DNA triplet that codes for the mRNA codon CGC undergoes a point mutation, after which the triplet codes for the mRNA codon CGU, the result, in terms of polypeptide synthesis, will be:
              2nd  -  G
    1st  - C || Arginine  ||  C  -  3rd
                   Arginine  ||  U

    A. the shifting of the reading frame in which RNA polymerase and the ribosome assess mRNA codons.
    B. the replacement of a valine residue with a leucine residue.
    C. none.
    D. the replacement of a histidine residue with a glutamine residue.
    C. is correct. A point mutation refers to a change within a portion of DNA such that a nucleotide residue is substituted for another nucleotide residue. If the substitution occurs within a triplet that actually transcribes and mRNA codon, then the resulting mRNA codon will be altered as well. Because the genetic code is degenerate, the alteration in the mRNA codon might or might not affect polypeptide synthesis. According to the genetic code both mRNA codons CGC and CGU code for the amino acid arginine. Consequently, the point mutation will not change the amino acid inserted into the growing polypeptide change.
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  607. The human somatic cell has twenty-two pairs of homologous chromosomes, called _______, plus one pair of _____ chromosomes.
    • Autosomes
    • sex chromosomes
  608. How are mitochondrial traits passed? (from whom)
    • They are passed onto offspring from the mother and only the mother.
    • This is because spermatozoom pass only twenty-three nuclear chromosomes to the zygote. The ovum also donates twenty-three nuclear chromosomes and all the other cellular components, including organelles. Since there is a very small and separate genome in the matrix of the mitochondria, all individuals inherit their mitochondrial genome (and any associated traits) from their mother. These traits are not recessive or dominant since there is only one copy it is either present or absent.
  609. How are Y-linked traits passed? (from whom)
    From father to son, since only males will have the Y-chromosome.
  610. How are the dominant and recessive traits carried on the X chromosome different in their expression the autosomal traits?
    • A male who carries a sex-linked (X-linked) recessive gene will be positive for the relevant phenotype because they only have one X chromosome. Males who are positive received the trait from their mother and will always pass the recessive gene to their daughter.
    • A female who is homozygous for a sex-linked recessive trait will be positive for the relevant phenotype, but who are heterozygous for a recessive sex-linked will be negative and will be called a carrier of the trait.
  611. If you see a pedigree on the MCAT (diagram with squares denoting men, circles for women, diamond for unknown, shaded for affected, unshaded for unaffected), a good strategy is to first determine the mode of inheritance. What is the best approach to do this?
    • 1. Check for Y-linked and mitochondrial inheritance. Both of these have very distinct patterns that can be easily spotted.
    • 2. Check for skipped generations. Is there a pattern such as "affected grandma, unaffected dad, affected son"? If so, the trait is probably recessive. If not, it is likely dominant.
    • 3. Check the ratio of affected males and affected females in this family. If there are approximately equal numbers, it suggests the trait is autosomal. If there are more males affected, the trait is likely X-linked. It is very rare for a trait to affect females more than males on the MCAT
  612. The Punnett square presented below indicates that:
    Image Upload
    A. on average, mating of a heterozygous and a homozygous recessive parent yields equal numbers of heterozygous and homozygous recessive offspring.
    B. on average, mating of heterozygous parents yields a 50-50 ratio of heterozygous and homozygous offspring.
    C. the parents produced four offspring.
    D. the probable outcome of heterozygous-homozygous matings is determined by the paternal chromosomal make-up.
    A. is correct. A Punnett square is used to determine the average or expected outcome of matings. They do not predict actual outcomes of individual pairings, which are subject to random variability of pairing of individual gametes. A Punnett square describes the statistical probability of the outcome of a mating between two individuals. It does not predict the number of offspring. This Punnett square indicates nothing about the mating of heterozygous parents. Although the ratio (fifty percent [Aa], fifty percent [aa]) looks like the paternal gametes (Aa), the maternal gametes (aa) play an equal part in determining the genotypes of offspring.
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  613. Which of the following is true regarding the pedigree shown below?
    Image Upload
    A. Phenotypic expression of autosomal recessive traits in offspring requires that both parents be heterozygous, or that one parent is heterozygous and the other is homozygous recessive.
    B. Phenotypic expression of autosomal recessive traits in parents must result in affected offspring.
    C. A trait illustrated in the pedigree is autosomal and sex-linked because both affected offspring and heterozygotes have affected or heterozygous fathers, and only generation III involves a carrier mother.
    D. The pedigree is incorrect because genotype for the trait should skip generations in autosomal recessive inheritance.
    A. is correct. Phenotypic expression of a recessive trait requires contribution of a recessive gene from each parent. A gene can, by definition, be autosomal or sex-linked, but cannot be both. Expression of an autosomal recessive trait does not have to skip generations. Heterozygous parents contribute either one or zero recessive genes each to a zygote. Using probability, one-quarter of offspring of such parents will be affected (homozygous for the abnormal gene) and one-quarter will be homozygous for the normal gene.
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  614. A researcher discovers that a particular human disease state is attributable to a single sex-linked recessive allele. She names the allele Z-3. In the course of her research, she studies an urban population and finds that the incidence of the disease is greater in men than in women. The most sensible explanation for the relatively high incidence of the disease in men is that:
    A. allele Z-3 is carried on the Y chromosome in males and on the X chromosome in females.
    B. allele Z-3 passes only from fathers to sons and not from mothers to sons.
    C. the Y chromosome carries no allele that will suppress expression of allele Z-3.
    D. independent assortment of homologous chromosome occurs during oogenesis but not during spermatogenesis.
    C. is correct. We are told that the Z-3 allele is sex-linked. That means it is carried on the X chromosome. Since a father does not impart an X chromosome to his male offspring, he cannot pass to a son an allele that is located on the X chromosome. Independent assortment is a "law" that applies to both spermatogenesis and oogenesis. The explanation for the researcher's observation pertains to the nature of sex-linked recessive alleles. In a female who is heterozygous for a sex-linked allele, one x chromosome carries the allele and the other carries an alternate allele. Since the disease-causing allele is recessive, the alternative allele dominates it, and the phenotype is not expressed. However, a male who carries the allele on his X chromosome has no second X chromosome to mask its expression. The Y chromosome does not do for the male what the second X chromosome does for the female. Although the sex-linked allele is recessive, it expresses itself in the male because his genome carries no alternative allele that will dominate it.
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  615. According to the law of independent assortment:
    A. homologous chromosomes enter the same gamete during meiosis.
    B. alternative alleles for a trait enter the same gamete during meiosis.
    C. the gene for each trait in an organism will segregate independent of those for other traits in the organism during meiosis.
    D. homologous chromosomes become separated into different gametes during meiosis.
    C. is correct.
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  616. Achondroplasia, a common cause of dwarfism, is an example of an autosomal dominant condition, which arises through mutation eighty percent of the time. The disorder is characterized by decreased cartilage production at the bone growth plates. Increased paternal age may increase the rate of this mutation. All of the following are true statements with regard to mutations EXCEPT
    A. a mutation can arise spontaneously.
    B. a mutation is always inherited by offspring.
    C. a mutation involves a change in the nucleotide sequence of DNA.
    D. a mutation can alter the production of a specific protein.
    B. is the statement that is not true in regard to mutations.
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  617. Among the following phenotypes, a trait included in the subcategory that comprises ten percent of Mendelian inheritance (X-linked dominant or recessive) is:
    A. eye color.
    B. color blindness.
    C. height.
    D. sickle cell anemia.
    B. is correct.
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  618. Describe fitness as it applies to the Darwinian concept of evolution.
    Fitness, as it applies to the Darwinian concept of evolution, is the ability of a gene to persist in the gene pool through successive generations. An organism that can survive and reproduce, passing on its genotype to its offspring, embodies Darwin's concept of evolution. Differential reproduction rates dictate that all available alleles for gene will not be inherited at equal rates from generation to generation. The factor that determines which genes persevere is natural selection. An organism possessing alleles for a trait that confers an advantage will more likely survive and, therefore, may reproduce more often than an organism that possesses an alternate form of the gene that does not confer advantage.
  619. Which one of the following is essential to the process of evolution?
    A. Unchanging gene pool
    B. Death of some mutant offspring before reproductive age
    C. Mutation
    D. Physical separation of two populations of the same species.
    C. is correct. The process of evolution depends on ongoing random mutation within a population. Those mutations that favor survival are promoted simply because the individuals that possess them are more likely to survive to reproductive age and to pass them on. The process of mutation does not require that some mutant offspring die before reproductive age (although this is a common event). Evolution is the alteration in gene pool composition in a given population of a species. It may proceed in the absence of any physical separation between two populations of the species.
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  620. Environmental changes might produce evolution by:
    A. halting the process of random mutation.
    B. inducing rapid and direct genetic change in response to the stresses imposed on the environment.
    C. producing mutations unfavorable to the altered environment.
    D. revealing the selective advantage conferred by a particular gene that is possessed by some but not all members of a population.
    D. is correct. Within the gene pool of a population, some genes have neither an advantageous nor a disadvantageous effect on the individual. Under some environmental change, however, such a gene might prove to be advantageous, and so confer a selective advantage on those individuals who posses it. Such individuals will be more likely to survive to reproductive age; as such, over some generations, the composition of the gene pool will change.
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  621. Jean Baptiste de Lamarck posited that an individual could pass on to its offspring a trait acquired in its lifetime. How does Lamarck's theory of evolution compare to the theory of evolution according to Darwin?
    Lamarck incorrectly theorized that an acquired trait, developed at some point during the organism's lifetime, was a heritable in the same manner that a gene arising through mutation would be heritable. Additionally, Lamarck's theory of evolution embraced a direction of evolution that entailed a continual quest (and reward) for self-improvement by the organism that is absent in evolution. According to Darwin's theory of evolution, only traits that are coded for by the genes in the gametes can be transferred to offspring. Furthermore, the advantage that a trait confers to an organism depends primarily on the environment in which the organism finds itself.
  622. Which of the following describes an instance of reproductive isolation?
    A. Each species of flycatcher, a bird, is associated with its own characteristic song.
    B. Two populations of frogs share a common ancestor but will no longer interbreed because their mating seasons do not overlap.
    C. A rattle snake becomes separated from other rattlesnakes and therefore cannot mate.
    D. Two distinct populations of the same species show subtle differences in traits and genotypes.
    B. is correct. Reproductive isolation requires two things: (1) that two populations once interbred, and (2) that they no longer do. Only this choice provides evidence that both of these criteria are met.
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  623. Define the term adaptive radiation. Describe two mechanisms that give rise tot his form of evolution. Does adaptive radiation increase or decrease biological diversity?
    Adaptive radiation is a form of evolution characterized by the creation of one or more new species that arise from a preexisting ancestral species. A key requirement for adaptive radiation is the reproductive isolation of a population of a species. One mechanism giving rise to adaptive radiation is geographical separation, such as what occurs with the development of a land bridge, the movement of a glacier, or the appearance of a mountain range (allopatric speciation). Another mechanism leading to adaptive radiation is the divergence of two gene pools of populations in habiting the same geographical region (sympatric speciation). Speciation can occur in this case when two populations are able to exploit different niches in the same environment. Either mechanism of adaptive radiation increases biological diversity by increasing the number of species that exist.
  624. Adaptive radiation results in all of the following EXCEPT:
    A. reduced competition.
    B. change of an organism's original niche.
    C. convergence of species.
    D. overall increase in the number of species.
    C. is the exception. It is the only choice that fails to describe an effect of adaptive radiation. Adaptive radiation entails a divergence of species, ultimately increasing biological diversity.
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  625. Which of the following is associated with both allopatric and sympatric speciation?
    A. Increased competition among original and newly developed species.
    B. Gross geographic separation
    C. Occupation of a new niche
    D. Decreased exploitation of resources.
    C. is correct. Both allopatric and sympatric speciation involved the occupation of a new niche by one or several populations, which in time gives rise to new species. "Gross geographic separation" describes allopatric speciation only. The two remaining choices are false for both allopatric and sympatric speciation; both will decrease competition among species and will increase the efficiency of exploitation of resources.
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  626. On what assumptions is the Hardy-Weinberg law premised?
    • 1) population size is very large
    • 2) mating is random
    • 3) mutation does not occur
    • 4) the population takes in no genes from other populations
    • 5) selection does not occur
  627. Consider four dogs and a trait for which
    -- 1 dog is homozygous dominant (TT)
    -- 2 dogs are homozygous recessive (tt) (tt), and
    -- 1 dog is heterozygous (Tt)
    Give the frequency of the T allele and the t allele.
    Give the Hardy-Weinberg law.
    • Simple counting tells us that the total number of alleles in this small population is 8. There are 3T alleles and 5 t alleles.
    • The frequency of the dominant (T) allele:
    • 5/8 = 0.625
    • The frequency of the recessive (t) allele:
    • 3/8 = 0.375
    • 0.625 + 0.375 = 1
    • Hardy-Weinberg law:
    • p + q = 1
    • (p + q)2 = 12
    • p2 + 2pq +q2 = 1
    • p2 = frequency of homozygous dominant
    • q2 = frequency of homozygous recessive
    • 2pq = frequency of heterozygous genotype
  628. Suppose that as to a trait (T) that manifests classic Mendelian inheritance, a population of 1 million individuals embodies 160,000 individuals homozygous for the recessive genotype (recognizable, of course, by their phenotype). What is the frequency of the homozygous recessive genotype and the frequency of the recessive allele? What is the frequency of the heterozygous genotype and the homozygous genotype?
    • Frequency of the homozygous recessive genotype:
    • q2 = 160,000/1,000,000 = 0.16
    • Frequency of the recessive allele:
    • q = √0.16 = 0.4
    • Frequency of the dominant allele:
    • p + (0.4) = 1; p=0.6
    • Frequency of the homozygous dominant genotype:
    • p2 = (0.6)2 =0.36
    • Frequency of the heterozygous genotype:
    • 2pq = 2(0.4)(0.6) = 0.48

    • Check the math:
    • 0.48 + 0.36 + 0.16 = 1.0
  629. The founder effect is a form of genetic drift that results when a small population colonizes a new area. All of the following would apply in the founder effect EXCEPT:
    A. the gene frequencies of an isolated colony may differ substantially from those of the larger population from which the colony broke off.
    B. any differences in the colony's gene frequency from its original population are more likely to be adaptive than random.
    C. members of the colony may possess only a small portion of the available alleles of the gene pool of the population they left behind.
    D. the population of the colony is sufficiently small for genetic drift to alter the gene pool.
    B. is correct. Genetic drift, of which the founder effect is one form, entails random changes in the allelic frequencies of populations. The other choices either list a common effect of genetic drift on a population or list conditions under which genetic drift may alter the gene pool.
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  630. Among the following, which will NOT alter the gene frequencies of a population?
    A. Genetic drift
    B. Mutation
    C. Natural selection
    D. Hardy-Weinberg equilibrium
    D. is correct. The Hardy-Weinberg law establishes the stability of gene frequencies When the Hardy-Weinberg law applies, the frequency with which a trait occurs in a population remains steady. A series of conditions must be met, however, in order for the Hardy-Weinberg law to take effect: large population, absence of mutations, absence of immigration or emigration, random reproduction, and the condition that any one gene has the same chance of reproducing as any other gene.
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  631. Give the order of classification from most comprehensive to most specific in taxonomy.
    kingdom, phylum, class, order, family, genus, and species

    King Phylum Courts Ordinary Farm GirlS
  632. Among phyla, when are the chordates identifiable? Of the chordates, how are vertebrates recognized?
    • Among phyla, the chordates are identifiable by the presence at some point during development of
    • (1) a dorsal nerve cord
    • (2) gill slits, and
    • (3) a notochord
    • Of the chordates, vertebrates are recognized by possession of
    • (a) a vertebral column
    • (b) a closed circulatory system
    • (c) a developed nervous system, and
    • (d) a developed sensory apparatus
  633. Order the following groupings of Homo sapiens (humans) according to the binomial system of classification: Mammalia (Class), Hominidae (Family), Chordata (Phylum), Vertebrata (Subphylum), Homo (Genus, Primata (Order), sapiens (Species), Animalia (Kingdom)
    • King Phylum Courts Ordinary Farm GirlS
    • Kingdom        Animalia
    • Phylum          Chordata
    •   Subphylum   Vertibrata
    • Class             Mammalia
    • Order             Primata
    • Family            Hominidae
    • Genus            Homo
    • Species          sapiens
  634. Give the three types of symbiosis.
    • mutualism: each partner derives benefit from the association and are frequently unable to survive independently of each other (ex. nitrogen-fixing bacteria and the legume root nodules they colonize)
    • commensalism: involves one partner that benefits from the symbiotic association and one partner that neither benefits nor is harmed (ex. epiphytes, small air plants, that use trees to anchor themselves)
    • parasitism: a relationship in which one organism benefits and the other is harmed.
  635. Among the following choices, which best describes the meaning of "fitness" in Darwinian terms?
    A. Ability to undergo random mutation
    B. Ability to adjust to changing environmental conditions
    C. Ability to escape predators
    D. Ability to reproduce
    D. is correct. The measure of "fitness" in Darwinian terms is the organism's ability to survive for as long as is necessary to reproduce.
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  636. Organisms belonging to Species X are in competition for resource R. One organism belonging to the species acquires by mutation the ability to use resource S as a substitute for resource R. Which of the following choices best describes the situation?
    A. Hardy-Weinberg law
    B. Genetic drift
    C. Competitive inhibition
    D. Adaptive radiation
    D. is correct. Adaptive radiation generally refers to the situation in which a subpopulation of a species is able to occupy a new ecological niche. Through additional evolution, its progeny adapt themselves to the new niche and may ultimately generate a separate species. Competitive inhibition refers to an enzyme-related phenomenon. The Hardy-Weinberg law accounts for the stability of gene frequencies in a large population that meets specific criteria. Genetic drift refers to changes in a small population's gene pool through random processes.
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  637. A biologically active agent, which completely diffuses through capillary beds, is injected into the brachiocephalic vein of the left arm. Which of the following would be most affected by the agent?
    A. Left arm
    B. Heart
    C. Right arm
    D. Lung
    D. is correct. Vein--> lung cap. The question can be translated to: if something enters a vein in your arm, where is the first capillary bed which will be encountered? The following is simply part of the basic cardiovascular anatomy: vein in arm (=upper body) --> larger veins --> superior vena cava --> right atrium of the heart --> right ventricle of the heart --> pulmonary artery --> smaller arteries in the lung --> arterioles in the lung --> capillary beds in the lung --> venules in the lung --> veins in the lung --> pulmonary veins --> left atrium of the heart--> left ventricle of the heart --> aorta --> many different arteries --> many different arterioles --> many different capillary beds of the body system including those that supply the heart muscle, the arms, the kidneys, the brain, the liver, etc. --) venules --> veins, and repeat.
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Card Set:
MCAT Biology Review
2013-09-23 22:26:22
MCAT Biology

MCAT Biology including Eukaryotic Cells, Genetic Material, Biology of Reproduction, Developing Organisms, Microbiology, Biochemical Pathways, and Human Physiology
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