Biology

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Biology
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  1. Evolution
    descent with modification; the idea that living species are descendants of ancestral species that were different from the present-day ones; also defined more narrowly as the change in the genetic composition of a population from generation to generation
  2. Biology
    the scientific study of life
  3. Emergent Properties
    new properties that arise with each step upward in the hierarchy of life, owing to the arrangement and interactions of parts as complexity increases
  4. The Biosphere
    the entire portion of Earth inhabited by life; the sum of all the planet's ecosytems
  5. Ecosystems
    all the organisms in a given area as well as the abiotic factors with which they interact; one or more communities and the physical environment around them
  6. Communities
    all the organisms that inhabit a particular area; an assemblage of populations of different species living close enough together for potential interaction
  7. Populations
    a localized group of individuals of the same species that can interbreed, producing fertile offspring
  8. Organ Systems
    a group of organs that work together in performing vital body functions
  9. Organs
    a specialized center of body function composed of several different types of tissues
  10. Tissues
    an integrated group of cells with a common function, structure, or both
  11. Cells
  12. Organelles
    any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells
  13. Molecules
    two or more atoms held together by covalent bonds
  14. Systems Biology
    an approach to studying biology that aims to model the dynamic behavior of whole biological systems
  15. Eukaryotic Cell
    • a type of cell with a membrane-enclosed nucleus and mebrane-enclosed organelles
    • organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotes
  16. Prokaryotic Cell
    • a type of cell lacking a membrane-enclosed nucleus and mebrane-enclosed organelles
    • organsims with prokaryotic cells (bacteria and archaea) are called prokaryotes
  17. DNA
    a double-stranded , helical nucleic acid molecule, consisting of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of being replicated and determining the inherited structure of a cell's proteins
  18. Genes
    a discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (orRNA, in some viruses)
  19. Genome
    the genetic material of an organism or virus; the complete complement of an organism's or virus's genes along with its noncoding nucleic acid sequences
  20. Bioinformatics
    the use of computers, software, and mathematical models to process and integrate biological information from large data sets
  21. Negative Feedback
    a primary mechanism of homeostasis, whereby a change in a physiological variable triggers a response that counteracts the initial change
  22. Positive Feedback
    a physiological control mechanism in which a change in a variable triggers mechanisms that amplify the change
  23. Domain Bacteria
  24. Domain Archaea
  25. Domain Eukarya
  26. Inquiry
    the search for information and explanation, often focused by specific questions
  27. Discovery Science
    the process of scientific inquiry that focuses on describing nature
  28. Data
    record observations
  29. Inductive Reasoning
    a type of logic in which generalizations are based on a large number of specific observations
  30. Hypothesis
    a tentative answer to a well-framed question, narrower in scope than a theory and subject to testing
  31. Deductive Reasoning
    a type of logic in which specific results are predicted from a general premise
  32. Controlled Expirement
    an expirement in which an experimental group is compared with a control group that varies only in the factor being tested
  33. Theory
    an explanation that is broad in scope, generates new hypothesism and is supported by a large body of evidence
  34. Models
    a representation of theory or process
  35. Technology
    the application of scientific knowledge for a specific purpose, often involving industry or commerce but also including uses in basic research
  36. Compound
    a substance consisting of two or more different elements combined in a fixed ratio
  37. Element
    any substance that cannot be broken down to any other substance by chemical reactions
  38. Trace Elements
    an element indispensible for life but required in extremely minute amounts
  39. Atom
    the smallest unit of matter that retains the properties of an element
  40. Neutrons
    a subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7 x 10-24g, found in the nucleus of an atom
  41. Protons
    a subatomic particle with a single positive electrical charge, with a mass of about 1.7 x 10-24 g, found in the nucleeus of an atom
  42. Atomic Nucleus
    an atom's dense central core, containing protons and neutrons
  43. Dalton
    a measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu
  44. Atomic Number
    the number of protons in the nucleus of an atom, unique for each element and designed by a subscript to the left of the elemental symbol
  45. Atomic Mass
    the total mass of an atom, which is the mass in grams of 1 mole of the atom
  46. Isotopes
    one of several atomic forms of an element, each with the same number of protons but a differen number of neutrons, thus differing in atomic mass
  47. Radioactive Isotope
    an isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy
  48. Energy
    the capacity to cause change, especially to do work (to move matter against an opposing force)
  49. Potential Energy
    the energy that ,atter posesses as a result of its location or spatial arrangement (structure)
  50. Electron Shells
    an energy level of electrons at a characteristic average distance from the nucleus of an atom
  51. Valence Electrons
    an electron in the outermost electron shell
  52. Valence Shell
    the outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom
  53. Orbital
    the three-dimensional space where an electron is found 90% of the time
  54. Chemical Bonds
    • an attraction between two atoms resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms
    • the bonded atoms gain complete outer electron shells
  55. Covalent Bond
    a type of strong chemical bond in which two atoms share one or more pairs of valence electron
  56. Molecule
    two or more atoms held together by covalent bonds
  57. Single Bond
    a single covalent bond; the sharing of a pair of valence electrons by two atoms
  58. Structural Formula
    a type of molecular notaion in which the constituent atoms are joined by lines representing covalent bonds
  59. Molecular Formula
    a type of molecular notaion representing the quanity of constituent atoms, but not the nature of the bonds that join them
  60. Double Bond
    a double covalent bond; the sharing of two pairs of valence electrons by two atoms
  61. Valence
    the bonding capacity of a given atoml usually equals the number of unpaired electrons required to complete the atom's outermost (valence) shell
  62. Electronegativity
    the attraction of a given atom for the electrons of a covalent bond
  63. Nonpolar Covalent Bond
    a type of covalent bond in which electrons are shared equally between two atoms of similiar electronegativity
  64. Polar Covalent Bond
    • a covalent bond betweena toms that differ in electronegativity
    • the shared electrons are pulled closer to the more elctronegative and the other atoms lightly positive
  65. Ion
    atom or group of atoms that has gained or lost one or more electrons, thus acquiring a change
  66. Cation
    a postively charged ion
  67. Anion
    a negatively charged ion
  68. Ionic Bond
    a chemical bond resulting from the attraction between oppositely charged ions
  69. Ionic Compounds
    a compound resulting from the formation of an ionic bond; also called a salt
  70. Salts
    a compound resulting from the formation of an ionic bond; also called an ionic compound
  71. Hydrogen Bond
    a type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule
  72. Van der Waals Interactions
    weak interactions between molecules or parts of molecules that result from localized charge fluctuations
  73. Reactants
    a staring material in a chemical reaction
  74. Products
    a material resulting from a chemical reaction
  75. Chemical Equilibrium
    in a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative conentration of the reactants and products do not change with time
  76. Polar Molecule
    a molecule (such as water) with opposite charges on different ends of the molecule
  77. Cohesion
    the binding together of like molecules, often hydrogen bonds
  78. Adhesion
    the attraction between different kinds of molecules
  79. Surface Tension
    • a measure of how difficult it is to stretch or break the surface of a liquid,
    • water has a high surface tension because of the hydrogen bonding of surface molecules
  80. Kinetic Energy
    • the energy associated with the relative motion of objects
    • moving matter can perfom work by imparting motion to the other matter
  81. Heat
    • the total amount of kinetic energy due to the random motion of atoms or molecules in a body of matter; also called thermal eneergy
    • heat is energy in its most random form
  82. Temperature
    a measure of the intensity of heat in degrees, reflecting the average kinetic energy of the molecules
  83. Celsius Scale
    a temperature scale (C) equal to 5/9 (F-32) that measures the freezing point of water at OC and the boiling point of water at 100C
  84. Calorie (cal)
    • the amount of heat energy required to raise the temperature of 1 g of water by 1C; also the amount of heat energythat 1 g of water releases when it cools by 1C
    • the Calorie (with capital C), usually used to indicate the energy content of food, is a kilocalorie
  85. Kilocalorie (kcal)
    a thousand calories; the amount of heat energy required to raise the temperature of 1kg of water by 1C
  86. Joule (J)
    a unit of energy: 1 J =0.2239 cal; 1 cal = 4.184 J
  87. Specific Heat
    the amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1C
  88. Heat of Vaporization
    the quanity of heat a liqid must absorb for 1 g of it to be converted from the liquid to the gaseseous state
  89. Evaporative Cooling
    the process in which the surface of an object becomes cooler during evaporation, owing to a change of the molecules with the greatest kinetic energy from the liquid to the gaseous state
  90. Solution
    a lquid that is a homogeneous mixture of two or more substances
  91. Solvent
    • the dissolving agent of a solution
    • water is the most versatile solvent known
  92. Solute
    a substance that is dissolved in a solution
  93. Aqueous Solution
    a solution in which water is the solvent
  94. Hydration Shell
    the sphere of water molecules around a dissolved ion
  95. Hydrophilic
    having an affinity for water
  96. Colloid
    a mixture made up of a liquid and particles that (because if their large size) remain suspended rather than dissolved in that liquid
  97. Hydrophobic
    having an aversion to water; tending to coalesce and form droplets in water
  98. Molecular Mass
    the sum of the masses of all the atoms in a molecule; sometimes called molecular weight
  99. Mole (mol)
    the number of grams of a substance that equals its molecular weight in daltons and contains Avogados's number of molecules
  100. Molarity
    a common measure of solute concentration, reffering to the number of moles of solute per litter of solution
  101. Hydrogen Ion
    • a single proton with a charge of 1+
    • the dissociation of a water molecule (H20) leads to the generation of a hydroxide ion (OH-) and a hydrogen ion (H+)
  102. Hydroxide Ion
    a water molecule that has lost a proton; OH-
  103. Hydronium Ion
    a water molecule that has an extra proton bound to it; H3O+
  104. Acid
    a substance that increases the hydrogen ion concentration of a solution
  105. Base
    a substance that reduces the hydrogen ion concentration of a solution
  106. pH
    a measure of hydrogen ion concentration equal to -log[H+] and ranging in value from 0 to 14
  107. Buffers
    a substance that consists of acid and base forms in a solution and that minimizes changes in pH when extraneous acids or bases are added to the solution
  108. Organic Chemistry
    the study of carbon compounds (organic compounds)
  109. Hydrocarbons
    an organic molecule consisting only of carbon and hydrogen
  110. Isomers
    • one of several compounds with the same molecular formula but different structures and therefore different properties
    • the three types of isomers are structural isomers, geometric isomers, and enantiomers
  111. Structural Isomers
    one of several compounds that have the same molecular formula but differ in the covalent arrangements of their atoms
  112. Geometric Isomers
    one of several compounds that have the same molecular formula and covalent arrangements but differ in the spatial arrangements of their atoms owing to the inflexibility of double bonds
  113. Enantiomers
    one of two compounds that are mirror images of each other
  114. Functional Groups
    a specific configuration of atoms commonly attached to the carbon skeletons of organix molecules and usually involved in chemical reactions
  115. Hydroxyl Group
    • a chemical group consisting of an oxygen atom joined to a hydrogen atom
    • molecules possessing this group are soluble in water and are called alcohols
  116. Carbonyl
    a chemical group present in aldehydes and ketones and consisting of a carbon atom double-bonded to an oxygen atom
  117. Carboxyl
    a chemical group presennt in organic acids and consisting of a single carbon atom double-bonded to an oxygen atom and also bonded to a hydroxyl group
  118. Amino
    • an organic molecule possessing both carboxyl and amino groups
    • amino acids serve as the monomers of polypeptides
  119. Sulfhydryl
    a chemical group consisting of a sulfur atom bonded to a hydrogen atom
  120. Phosphate
    a chemical group consisting of a phosphorus atom bonded to four oxygen atoms; important in energy transfer
  121. Methyl
    • a chemical group consisting of a carbon bonded to three hydrogen atoms
    • the methyl group may be attached to a carbon or to a different atom
  122. Adenosine Triphosphate
    • ATP
    • an adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed
    • this energy is used to drive energonic reactions in cells
  123. Macromolecules
    • a giant molecule formed by the joining of smaller molecules, usually by a condensation reaction
    • polysaccharides, proteins, and nucleic acids are macromolecules
  124. Polymer
    a long molecule consisting of many similar or identical monomers linked together
  125. Monomers
    the subunit that serves as the building block of a polymer
  126. Carbohydrates
    a sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides)
  127. Lipids
    one of a group of compounds, including fats, phospholipids, and steroids, that mix poorly if at all, with water
  128. Proteins
    a functional biological molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure
  129. Nucleic Acids
    • a polymer (ppolynucleotide) consisting of many nucleotide monomers; serves as blueprint for proteins and, through the actions of proteins, for all cellular activities
    • the two types are DNA and RNA
  130. Condesation Reaction
    a reaction in which two molecules become covalently bonded to each other through the loss of a small molecule, usually water, in which case it is also called a dehydration reaction
  131. Dehyrdration Reaction
    a chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule
  132. Enzymes
    a macromolecule serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction
  133. Hydrolysis
    a chemical process that lyses, or splits, molecules by the addition of water, functioning in disassembly of polymers to monomers
  134. Monosaccharides
    • the simplestcarbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides
    • also known as simple sugars, monosaccharides have molecular formulas that are generally some multiple of CH20
  135. Disaccharide
    a double sugar, consisting of two monosaccharides joined by a glycosidic linkage formed during dehydration synthesis
  136. Glycosidic Linkage
    a covalent bond formed between two monosaccharides by a dehydration reaction
  137. Polysaccharides
    a polymer of many monosaccharides, formed by dehydration reactions
  138. Starch
    a storage polysaccharide in plants, consisting entirely of glucose monokmers joined by alpha glycosidic linkages
  139. Glycogen
    an extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch
  140. Cellulose
    a structural polysaccharide of plant cell walls, consisting of glucose monomers joined by beta glycosidic linkages
  141. Lipids
    one of a group of compounds, including fats, phospolipids, and steroids, that mix poorly, if at all, with water
  142. Fat
    a lipid consisting of three fatty acids linked to one glycerol molecule; also called a triclyglycerol or triglyceride
  143. Fatty Acid
    • a long carbon chain carboxylic acid
    • fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form a fat molecule, also known as a triglycerol or triglyceride
  144. Triacylglycerol
    three fatty acids linked to one glycerol molecule; also called a fat or a triglyceride
  145. Saturated Fatty Acid
    a fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that are attached to the carbon skeleton
  146. Unsaturated Fatty Acid
    • a fatty acid possesing one or more double bons between the carbons in the hydrocarbon tail
    • such bonding reduces the number of hydrogen atoms attached to the carbon skeleton
  147. Trans Fats
    an unsaturated fat containing one or more trans double bonds
  148. Phospholipids
    • a lipid made up of glycerol joined to two fatty acids and a phosphate group
    • the hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head
    • phospholipids form bilayers that function as biological membranes
  149. Cholestrol
    a steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as hormones
  150. Steroids
    a type of lipid characterized by a carbon skeleton consisting of four rings with various chemical groups attached
  151. Enzymes
    a macromolecule serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction
  152. Catalysts
    a chemical agent that increases the rate of a reaction without being used or consumer by the reaction
  153. Transport Proteins
    a transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane
  154. Motor Proteins
    a protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell
  155. Polypeptides
    a polymer (chain) or many amino acids linked together by peptide bonds
  156. Peptide Bond
    the covalent bond between the carboxyl group on one amino acid and the amino group on another; formed by a dehydration reaction
  157. Primary Structure
    the level of protein structure referring to a specific sequence of amino acids
  158. Secondary Structure
    the localized, repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bond formation between constituents of the backbone
  159. Tertiary Structure
    irregular contortions of a protein molecule due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges
  160. Hydrophobic Interaction
    a type of weak chemical bond formed when molecules that do not mix with water coalesce to exclude water
  161. Disulfide Bridges
    a strong covasalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer
  162. Quaternary Structure
    the particular shape of a complex, aggregate protein, defined by the characteristics three-dimensional arrangement of its constituent subunits, each a polypeptide
  163. Denaturation
    • in proteins, a process in which a protein unravels and loses its native shape, thereby becoming biologically inactive; in DNA, the seperation of two strands of the double helix
    • denaturation occures under extreme (noncellular) conditions of pH, salt concentration, and temperature
  164. Chaperonins
    a protein molceule that assist in the proper folding of other proteins
  165. X-Ray Crystallography
    a technique that depends on the diffraction of an X-ray beam by the individual atoms of a crystallized molecule tostudy the three-dimensional structure of the molecule
  166. Nucleic Acids
    • a polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities
    • the two types are DNA and RNA
  167. Ribonucleic Acid (RNA)
    a type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogen bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis, gene regulation, and as the genome of some viruses
  168. Polynucleotides
    a polymer of consisting of many nucleotide monomers in a chain; nucleotides can be those of DNA or RNA
  169. Nucleotides
    the building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group
  170. Pyrimidine
    • one of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring
    • cytosine (C), thymine (T), and uracil (U) are pyrimidines
  171. Purines
    • one of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused toa five membered ring
    • adenine (A), and guanine (G) are purines
  172. Ribose
    the sugar component of RNA nucleotides
  173. Deoxyribose
    the sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides
  174. Double Helix
    the form of native DNA, refering to its two adjavent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape
  175. Antiparallel
    the opposite arrangement of the sugar-phosphate backbones in a DNA double helix
  176. Light Microscope (LM)
    an optical instrument with lenses that refract (bend) visible light to magnify images of specimens
  177. Electron Microscope (EM)
    • a microscope that uses magnets to focus an electron beam on or through a specimen, resulting in resolving power a thousandfold greater than that of a light microscope
    • a transmission electron microscope (TEM) is used to study the internal structure of thin sections of cells
    • a scanning electron microscope (SEM) is used to study the fine details of cell surfaces
  178. Cell Fractionation
    the disruption of a cell and separation of it sparts by centrifugation
  179. Cytosol
    the semifluid portion of the cytoplasm
  180. Nucleoid
    a dense region of DNA in a prokaryotic cell
  181. Cytoplasm
    the contents of the cell, exclusive of the nucleus and bounded bythe plasma membrane
  182. Plasma Membrane
    the membrane at the boundary of every cell that acts as a selective barrier, regulation the cell's chemical composition
  183. Animal Cells
  184. Plant Cells
  185. Nuclear Envelope
    the double membrane in a eukaryotic cell that encloses the nucleus, seperating it from the cytoplasm
  186. Nuclear Lamina
    a netlike array of protein filaments lining the inner surface of the nuclear envelope; it helps maintain the shape of the nucleus
  187. Chromosomes
    • a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells
    • each chromosome consists of one very long DNA molecule and associated proteins
  188. Chromatin
    • the complex of DNA and proteins that makes up a eukaryotic chromosome
    • when the cell is not divinding, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light miroscope
  189. Nucleolus
    a specialized structure in the nucleus, consisting of chromatin regions containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasmis site of rRNA sunthesis and ribosomal subunit assembly
  190. Ribosomes
    • a complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit
    • in eurkaryotic cells, each subunit is assebled in the nucleolus
  191. Endomembrane System
    the collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of memraneous vesicles; includes the smooth and rough endoplasmic reticulum, the golgi apparatus, lysosomes, and vacuoles
  192. Vesicles
    a sac made of membrane in the cytoplasm
  193. Endoplasmic Reticulum (ER)
    an extensive membranenous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions
  194. Smooth ER
    that portion of the ER that is free of ribosomes
  195. Rough ER
    that portion of the ER studded with ribosomes
  196. Glycoproteins
    a protein with one or more carbohydrates covalently attached to it
  197. Transport Vesicles
    a tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cell
  198. Golgi Apparatus
    an organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates
  199. Lysosome
    a membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists
  200. Phagocytosis
    • a type of endocytosis in which large particulate substances are taken up by a cell
    • it is carried out by some protist and by certain immune cells of animals (in mammals, maunly macrophaages, neutrophils, and dendritic cells)
  201. Food Vacuoles
    a membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell
  202. Contractile Vacuoles
    a membranous sac that helps move excess water out of certain freshwater protists
  203. Central Vacuole
    a membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development
  204. Mitochondria
    an organelle in eukaryotic cells that serves as the site of cellular respiration
  205. Chloroplasts
    an organelle found in plants and photosynthetic protist that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water
  206. Peroxisome
    an organelle containing enzymes that transfer hydrogen (H2) from various substrates to oxygen (O2) producing and then degrading hydrogen peroxide (H2O2)
  207. Mitochondrial Matrix
    the compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle
  208. Cristae
    an infolding of the inner membrane of a mitochondrion that houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase)
  209. Plastids
    • one of a family closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts (leucoplasts)
    • plastids are cound in cells of photosynthetic organism
  210. Thylakoids
    • a flattened membrane sac inside a chloroplast
    • thylakoids exist in an interconnected system in the chloroplast and contain the molecular "machinery" used to conveert light energy to chemical energy
  211. Granum
    • a stack of membrane-bounded thylakoids in the chloroplast
    • grana function in the light reactions of photsynthesis
  212. Stroma
    within the chlorooplast, the dense fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water
  213. Cytoskeleton
    a network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions
  214. Motor Proteins
    a protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell
  215. Microtubules
    a hollow rod composed of tubilin proteins that make up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella
  216. Centrosome
    structure present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center:a centrosome has two centrioles
  217. Centrioles
    • a structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern
    • a centrosome has a pair of centrioles
  218. Flagella
    • a long cellular appendage specialized for locomotion
    • like motile cilia, eukaryotic flagella have a core with nine outer doublet microtubules and two inner ingle micrutubules ensheathed in an extension of the plasma membrane
    • prokaryotice flagella habe adifferent structure
  219. Basal Body
    • a eukaryotic cell structure consisting of a 9 + 0 arrangement of microtubule triplets
    • the basal body may organize the microtubule assembly of a cilium or flagellum and is structurally very similar to a centriole
  220. Dyneins
    • in cilia and flagella, a large contractile protein esxtending from one mirotubule doublet to the adjacent doublet
    • ATP hydrolysis drives changes in dynein shape that lead to bending of cilia and flagella
  221. Microfilaments
    a cable composed of actin proteins in the cytoplast of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or wiht myosin to cause cell contraction; also known as actin filament
  222. Actin
    a globular protein that links into chains, two of which twist helically about each other, forming microfilaments (actin filaments) in muscle and other kinds of cells
  223. Cortex
    • (1) the outer region of cytoplasm in a eukaryotic cell, lying just under the plasma membrane, that has a more gel-like consistency than the inner regions, due to the presence of multiple microfilaments
    • (2) in plants gorund tissue that is between the vascular tissue and dermal tissue in a root or eudicot stem
  224. Myosin
    a type of protein filament that acts as a motor protein with actin filaments to cause cell contraction
  225. Pseudopodia
    a cellular extension of amoeboid cells used in moving and feeding
  226. Cytoplasmic Streaming
    a circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of material within cells
  227. Intermediate Filaments
    a component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments
  228. Cell Wall
    • a protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists
    • polysaccharides such as cellulose (in plants and some protists), chitin (
    • in fungi), and peptioglycan (in bacteria) are an important structural component of cell walls
  229. Primary Cell Wall
    in plants, a relatively thin and flecible layer first secreted by a young cell
  230. Middle Lamella
    in plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells
  231. Secondary Cell Wall
    in plants, a strong and durable matrix often deposited in several laminated layers for cell protection and support
  232. Extracellular Matrix (ECM)
  233. Collagen
    a glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom
  234. Proteoglycans
    • a glycoprotein consisting of a small core protien with many carbohydrate chains attached, found in the cellular matrix of animals
    • a proteoglycans may consists of up to 95% carbohydrate
  235. Fibronectin
    a glycoprotein that helps animal cells attach to the extracellular matrix
  236. Integrins
    in animal cells, a transmembrane receptor protein that interconnects the extracellular matric and the cytoskeleton
  237. Plasmodesmata
    an open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent
  238. Selective Permeability
    a property of biological membranes that allows them to regulate the passage of substances
  239. Amphipathic
    having both a hydrophilic region and a hydrophobic region
  240. Fluid Mosaic Model
    the currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecule drifting laterally in a fluid bilayer of phospholipids
  241. Integral Proteins
    typically a transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqeuous solution on either sife of the membrane (or lining the channel in case of a channel protein)
  242. Glycolipids
    a lipid with a covalently attached carbohydrate
  243. Glycoproteins
    a protein with one or more carbohydrates covalently attached to it
  244. Transport Proteins
    a transmebrane protein that helps a certain substance or class of closely related substance to cross the membrane
  245. Aquaporins
    a channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of water across the membrane
  246. Diffusion
    the spontaneous movement of a substnace downits concentration gradient, from a region where it is more concentrated to a region where it is less concentrated
  247. Concentration Gradient
    a region along which the density of a chemical substance increases or decreases
  248. Passive Transport
    the diffusion of a substance accross a biological membrane with no expenditure of energy
  249. Osmosis
    the diffusion of water across a selectively permeable membrane
  250. Tonicity
    the ability of a solution surrounding ca cell to cause that cell to gain or lose water
  251. Isotonic
    referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell
  252. Hypertonic
    referring to a solution that, when surrounding a cell, will cause the cell to lose water
  253. Hypotonic
    referring to a solution that, when surrounding a cell, will cause the cell to take up water
  254. Osmoreregulation
    regulation of sultoe concentrations and water balane by a cell or organism
  255. Flaccid
    limp. lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell
  256. Plasmolysis
    a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment
  257. Facilitated Diffusion
    the spontaneous passage of molecules or ions across a biological membrane with the assistance of specific transmembrane transport proteins
  258. Ion Channels
    a transmembrane protein channel that allows a specific ion to flow across the mrembrane down its concentration gradiet
  259. Gated Channels
    a transmembrane protein channel that opens or closes in response to a particular stimulus
  260. Active Transport
    the movement of a substance across a cell membrane, wiht an expenditure of energy, against its concentration or electrochemical gradient; mediated by specific transport proteins
  261. Sodium-Potassium Pump
    a transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell
  262. Membrane Potential
    • the difference in electrical charge (voltage) across a cell's plasma membrane, due to the differential distribution of ions
    • membrane potential affects the activity of excitable cells and the transmembrane movement of all charge substances
  263. Electrochemical Gradient
    the diffusion gradient of an ion, whwich is affected by both the concetration difference of the ion across a membrane (a chemical force) and the ion's tendency to move relative to the membrane potential 9 an electron force)
  264. Electrogenic Pump
    an ion transport protein that generates volage across a membrane
  265. Proton Pump
    an active transport protein in cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process
  266. Cotransport
    the coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient
  267. Exocytosis
    the cellular secretion of biological molecules by the fusion of vesicle containing them with the plasma membrane
  268. Endocytosis
    cellular uptake of biological molecules and particulate matter via formation of neq vesicles from the plasma membrane
  269. Phagocytosis
    • a type of endocytosis in which large particulate substances are taken up by a cell
    • it is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells)
  270. Receptor-Mediated Endocytosis
    the movement of specific molecules into a cell by th einward budding of memebranous vesicles containing proteins with receptor sites specific to the molecules being taken in;enables a cell to aquire bulk quanities of specific sunstance
  271. Pinocytosis
    a type of endocytosis in qhich the cell ingests extracellular fluids and its dissolved solutes
  272. Ligands
    a molecule that binds specificaly to another molecule, usually a larger one
  273. Metabolism
    the totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which ,manage the material and energy resources of the organism
  274. Metabolic Pathway
    a series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule into simpler compounds (Catabolic pathway)
  275. Catabolic Pathways
    a metabolic pathway that releases energy by breaking down complex molecules to simpler compounds
  276. Anabolic Pathways
    a metabolic pathway that consumes energy to sunthesize a complex molecule from simpler compounds
  277. Bioenergetics
    • (1) the overall flow and transformation of energy in an organism
    • (2) the study of how energy flows through organisms
  278. Energy
    the capacity to cause change, especially to do work (to move matter against an opposing force)
  279. Kinetic Energy
    • the energy associated with relative motion of objects
    • moving matter can perform work by imparting motion to other matter
  280. Heat
    • the total amount of kinetic energy due to the random motion of atoms or molecules in a body of matterl also called thermalenergy
    • heat is energy in its most random form
  281. Potential Energy
    the energy that matter posesses as a result of its location or spatial arrangement (structure)
  282. Chemical Energy
    energy available in molecules for release in a chemical reaction; a form of potential energy
  283. Thermodynamics
    the study of energy transformation that occur in a collection of matter
  284. First Law of Thermodynamics
    the principle of conservation of energy: energy can be transferred and transformed, but it cannot be created or destroyed
  285. Entropy
    a measure of disorder, or randomness
  286. Second Law of Thermodynamics
    • the principle stating that eevery energy transfer or transformation increases the entropy of the universe
    • ordered forms of energy are atleast partly converted to heat
  287. Free Energy
    the portion of a biological system's energy that can perform work when temperature and pressure are uniform throughout the system (delta G)
  288. Exergonic Reaction
    a spontatneous chemical reaction, in which there is a net realeaseof free energy
  289. Endergonic Reaction
    a nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings
  290. Energy Coupling
    in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction
  291. ATP (Adenosine Triphosphate)
    • an adenine-containing nucleosidic triphosphate that releases free energy when its phosphate bonds are hydrolyzed
    • this energy is used to drive endergonic reactions in cells
  292. Phosphorylated
    referring to a molecule that is covalently bonded to a phosphate group
  293. Enzyme
    a macromolecule serving as a catalyst, a chemical agent that changes the rate of a reaction wihtout being consumed by the reaction
  294. Catalyst
    a chemical agent that increases the rate of a reaction without being consumed by the reaction
  295. Activation Energy
    the amount of energy that reactants must abosorb before a chemical reaction will start; also called free energy of activation
  296. Substrate
    the reactant of which an enzyme works
  297. Enzyme-Substrate Complex
    a temporar complex formed when an enzyme binds to its substate molecules
  298. Active Site
    the specificportion of an enzyme that binds th substrate by means od multiple weak interactionsand that forms the pocket in which catalysis occurs
  299. Induced Fit
    induced by entry of substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate
  300. Cofactors
    • any nonprotein molecule or ion that is required for the proper functioning of an enzyme
    • cofactors can be permanently bound to the active site or may bind loosely with the substrate during catalysis
  301. Coenzyme
    • an organic molecule serving as a cofactor
    • most vitamins function as coenzymes in metabolic reactions
  302. Competitive Inhibitors
    a substance that reduces the activity of an enzyme by enetering the active site in place of the substrate whose structure it mimics
  303. Noncompetitive Inhibitors
  304. Allosteric Regulation
    the binding of a regulatory molecule to a protein at one site that affects the functions of the protein at a different site
  305. Cooperativity
    a kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the others, facilitating binding of subsequent substrate molecules
  306. Feedback Inhibition
    a method of metabolic control in which the end product of a metbolic pathways acts as an inhibitor of an enzyme within that pathway
  307. Fermentation
    a catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such at ethyl alcohol or lactic acid
  308. Aerobic Respiration
    • a catabolic pathway that consume oxygen (O2) and organic molcules, producing ATP
    • this is the most efficient catabolic pathway and is carried out in most eukaryotic cells and many prokaryotic organisms
  309. Cellular Respiration
    the catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules for the production of ATP
  310. Redox Reactions
    a chemical reaction involving the complete or partial transfer of one or more elctrons from one reactant to another; short for oxidation-reduction reaction
  311. Oxidation
    the loss of electrons from a substance involved in a redox reaction
  312. Reduction
    the addition of electrons to a substance involved in a redox reaction
  313. Reducing Agent
    the electron donor in a redox reaction
  314. Oxidizing Agent
    the electron acceptor in a redox reaction
  315. NAD
    nicotinamide adenine dinucleotide, a coenzyme that cann accept an electron and acts as an electron carrier in the elctron transport chain
  316. Electron Transport Chain
    • a sequence of electron carrier molecules (
    • membrane proteins) thazt shuttle electrons during the redox reactions that release energy used to make ATP
  317. Glycolysis
    • the spitting of glucose into pyruvate
    • glycolysis occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration
  318. The Citric Acid Cycle
    a chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in gllycolysis by oxidizing pyruvate to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; the second major stage in cellular respiration
  319. Oxidative Phosphorylation
    the production of ATP using energy derived from the redox reactions of an electron transport chain, the thiird major stage of cellular respiration
  320. Chemiosmosis
    • an energy-coupling mechanism that uses energy sotrd in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP
    • most ATP sunthesis in cells occurs by chemiosmosis
  321. Substrate-Level Phosphorylation
    the formation of ATP by an enzyme directly transferring a phsophate gorup to ADP from an intermediate substrate in catabolsim
  322. Acetyl CoA
    acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme
  323. Cytochromes
    an iron-containing protein that is a component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic cells
  324. ATP Synthase
    • a complex of several membrane proteins that drive a port through which protons diffuse
    • this complex function in chemiosmosis with adjacent electron trsport chains, using the energy of a hyrgen ion ( proton) concentration gradient to make ATP
    • ATP synthases are found in the inner mitochondrial membrane of eukaryotic cells and in the plasma membrane of prokaryotes
  325. Proton-Motive Force
    the potential energy stored in the form of an electrocheical gradient, generated by the pumping of hydrogen ions across a biological membrane during chemiosmosis
  326. Alcohol Fermentation
    glycolysis followed by the conversion of pyruvate to carbon dioxide and ethyl alcohol
  327. Lactic Acid Fermentation
    glycolysis followed by the conversion of pyruvate to lactate, with no release of carbon dioxide
  328. Obligate Anaerobes
    • an organism that only carries out fermentation or anaerobi respiration
    • such organisms cannot use oxygen and in fact may be poisoned by it
  329. Facultative Anaerobes
    an organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present
  330. Beta Oxidation
    a metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA
  331. Photosynthesis
    the conversion of light energy to chemical energy that is stored in sugars or other organic compounds; occurs in plants, algae, and certain prokaryotes
  332. Autotrophs
    • an organism that obtains organic food molcules without eating other organisms
    • autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones
  333. Chlorphyll
    • a green pigment located within the chloroplasts of plants and algae and in the membranes of certain prokaryotes
    • chlorophyll a participates directly in the light reactions, which convert solar energy to chemical energy
  334. Mesophyll
    the ground tissue of a leaf, sanwhiched between the upper and lower epidermis and specialized for photosynthesis
  335. Stomata
    a microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant
  336. Stroma
    within the chloroplast , the dense fluid of the chloroplast surrounding the thylakoid membrane, involved in the synthesis of organic molecules from carboin dioxide and water
  337. Thylakoids
    • a flattened membranous sac inside a chloroplast
    • thylakoids exist in an interconnected system in the chloroplast and contain the molecular "machinery" used to convert light energy to chemical energy
  338. Light Reactions
    • the first of two major stages in photsynthesis (preceding the calvin cycle)
    • these reactions, which occur on the thylakoid memrbanes of the chloroplast or on membranes of certian prokaryotes, convert solar energy to the chemical energy of ATO and NADPH, releasing oxygen in the process
  339. Calvin Cycle
    the second of two major stages in photsynthesis (following the light reactions), involving fixation of atmosphereic CO2 and reduction of the fixed carbon into carbohydrate
  340. NAPD+
    nicotinamide adenine dinucleotide phosphate, an lectron acceptor that, as NADPH, temporarily stores energized electrons produced during the light reactions
  341. Photophosphorylation
    the process of generating ATP from ADP and phosphate by means of a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certain prokaryotes during the light reactions of photosynthesis
  342. Carbon Fixation
    the intiial incorporation of carbon from CO2 into an organic compound by an autotrophic organism ( a plant, another photosynthetic organism, or a chemoautotrophic prokaryote)
  343. Wavelength
    the distance between crests of waves, such as those of the electromagnetic spectrum
  344. Electromagnetic Spectrum
    the entire spectrum of electromagnetic radiation ranging in wavelength from oless than a nanometer to more than a kilometer
  345. Visible Light
    the light portion of the electromagnetic spectrum that can be detected ad various colors by the human eye, ranging in wavelength from about 380 nm to about 750 nm
  346. Photons
    a quantum, or discrete quanity, of light energy that behaves as if it were a particle
  347. Spectrophotometer
    an instrument that measures the proportions of light of different wavelengths absorbed and transmitted bya pigment solution
  348. Absorption Spectrum
    the range of a pigment's ability to absorb various wavelengths of light; also a graph of such a range
  349. Chlorophyll a
    a photsyntehtic pigment that participates directly in the light reactions, which convert solar energy to chemical energy
  350. Action Spectrum
    a graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process
  351. Chlorophyll b
    an accesory photosynthetic pigment that transfers energy to chlorophyll a
  352. Carotenoids
    • an accessory pigment, either yellow or orange, in the chloroplasts of plants and in some proakaryotes
    • by absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drie photosynthesis
  353. Photosystem
    • a light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes
    • there are two types of photosystems, I and II; they absorb light best at different wavelengths
  354. Reaction-Center Complex
    • a complex of proteins associated with a special apir of chlorphyll a molecules and a primary electron acceptor
    • located centrally in a photosystem, this complex triggers the light reactions of photsynthesis
    • excited by light energy, the pair of chlorphylls donates an electron the the primary electron acceptor, which passes an electron to an electron transport chain
  355. Light-Harvesting Complex
    a complex of proteins associated with pigment molecules (including chlorophyll a, b, and carotenoids) that captures light and energy trnasfers it to reaction-center pigments in a photosystem
  356. Primary Electron Acceptor
    in the thylakoid membrane of a chloroplast or in the membrane of some prokaryotes, a specialized molecule that shares the reaction-center complex with a pair of chlorophyll a molcules and that accepts an electron from them
  357. Photosystem II
    one of two light-capturing units in chloroplasts' thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of p680 chlorophyll a at its reaction center
  358. Photosystem I
    one of two light-capturing units in a chloroplast's thylakoid membrane of some prokaryotes; it has two molecules of p700 chlorophyll a at its reaction center
  359. Linear Electron Flow
    • a route of electron flow during the light reactions of photosynthesis that involves both photosystems I and II and produces ATP, NADPH, and O2
    • the net electron flow is from H20 to NADP+
  360. Cyclic Electron Flow
    a route of electron flow during the light reactions of photosynthesis that involves only photosystem I and that produces ATP but ot NADPH or O2
  361. Glyceraldehyde-3-Phospate (G3P)
    a three-carbon carbohydrate that is the direct product of the calvin cycle; it is also an intermediate in glycolysis
  362. Carbon Fixation
    the initialincorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photsynthetic organism, or a chemoautomtrophic prokaryote)
  363. Reduction
    the addition of electrons to a substance involved in a redox reaction
  364. C3 Plants
    a plant that uses the calvin cycle for the initital steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate
  365. Photorespiration
    • a metabolic pathway that consumes oxygen and ATP, releases carbon diovide, and decreases photosynthetic output
    • photrespiration generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide
  366. C4 Plants
    a plant in which the calvin cycle is preceded by reaction that incorpoarate CO2 into four-carbon compound, the end product of which supplies CO2 for the calvin cycle
  367. Bundle-Sheath Cells
    in C4 plants, a type eof photsynthetic cell arranged into tightly packed sheaths around the veins of a leaf
  368. Mesophyll Cells
    in C4 plants, a typpe of loosely arranged photosynthetic cell located between the bundle sheath and the leaf surface
  369. CAM Plants
    a plant that uses crassulacean acid metabolism, an adaption for photosynthesis dioxide entering open stomata during the night is converted to organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed
  370. Cell Division
    the reproduction of cells
  371. Cell Cycle
    an ordered sequence of events in the ife of a cell. from its origin in the division of a parent cell until its own division of a parent ceoll until its own division into two; the eukaryotic cell cycle is composed of interphase (including G1, S, and G2 subphases) and M phase (including mitosis and cytokinesis)
  372. Genome
    the genetic material of an organsim or virus; the complete ocmplement of an organism's or viruses's genes along with its noncoding nucleic acid sequences
  373. Somatic Cells
    any cell in a multicellular organism except a sperm or egg
  374. Sister Chromatids
    • either of two copies of a duplicated chromosome attached to each other by proteins at the centromere and, sometimes, along the arms
    • while joined, two sister chromatids make up one chromosomes; chromatids are eventually serperated during mitosis or meiosis
  375. Centromere
    the specialized region fo the chromosomes where two sister chromatids are most closely attached
  376. Mitosis
    • a process of nuclear divison in eukaryotic cells conventionally divided into five stages; prophase, prometaphase, metaphase, anaphase, and telophase
    • mitosis conserves chromosomes equally to each of the daughter nuclei
  377. Cytokinesis
    the division of the cytoplasm to form two seperate daughter cells immediately after mitosis, meiosis I, or meiosis II
  378. Meiosis
    • a modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication
    • it results in cells with half the number of chromosome sets as the original cell
  379. Mitotic Phase
    the phase of the cell cucle that includes mitosis and cytokinesis
  380. Interphase
    • the period in a cell cycle when the cell is not dividing
    • during interphase, cellular metabolic activity is high, chromosomes and organellas are duplication, and cell size may invrease
    • interphase accounts for 90% of the cell cyle
  381. G1 Phase
    the first gap or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins
  382. S Phase
    the synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated
  383. G2 Phase
    the second gap or growth phase, of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs
  384. Prometaphase
    the second stage of mitosis, in which discrete chromosomes consisting of identical sister chromatids appear, the nuclear envelope fragments, and the spindle micrtubules attach to the kinetochores of the chromosomes
  385. Metaphase
    the thrid stage of mitosis, in which the spindle is complete and the chromosomes, attached to mictrubules at their kinectochores, are all aligned at the metaphase
  386. Anaphase
    the fourth stage of mitosis, in which the chromatids of each chromosome have sperated and the daughter chromosomes are moving to the poleds of the cell
  387. Prophase
    the first stage of mitosis, in which the chromatin condenses, the mitotic spindle begins to form, and the nucleolus disappears, but the nucleus remains intact
  388. Telophase
    the fifth and final stage of mitosis, in which daughter nuclei are forming and cytokenesis has typically begun
  389. Mitotic Spindle
    an assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis
  390. Centrosome
    • structure present in the cytoplasm of animal cells, important durin cell division; functions as a microtubule-organizing center
    • a centrosome has two centrioles
  391. Aster
    a radial array of short microtubules that extendss from each centrosome toward the plasma membrane in an animal cell undergoing mitosis
  392. Kinectochore
    a structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle
  393. Metaphase Plate
    an imaginary plane midway between the two poles of a cell in metaphase on which the centromers of all the duplicated chromosomes are located
  394. Cleavage
    • (1) the process of cytokensis in animall cells, characterized by pinching of the plasma membrane
    • (2) the succession of rapid cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells
  395. Cleavage Furrow
    the first sign of cleavage in an animall cell; a shallow groove in the cell surface near the old metaphase plate
  396. Cell Plate
    a double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis
  397. Binary Fusion
    • a method of asexual reproduction by "division in half"
    • in prokaryotes, binary fission does not involve mitosis; but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process
  398. Cell Cycle Control System
    a cyclically operating set of molecules in the eukaryotic cell that both triggers and coordinates key events in the cell cycle
  399. Checkpoint
    a control point in the cell cycle where stop and go-ahead signals can regulate the cycle
  400. G0 Phase
    a nondividing state occupied by cells that have left the cell cycle
  401. Cyclin
    a cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle
  402. Cyclin-Dependent Kinases (Cdks)
  403. MPF
    • maturation-promoting factor (M-phase promoting factor); a protein complex required for a cell to progress from late interphase to mitosis
    • the active form consists of cyclin and a protein kinase
  404. Growth Factor
    • (1) a protein must be present in the extracellular environment (culture medium or animal body) for the growth and normal deveoplment of certain types of cells
    • (2) a local regulator that acts on nearby cells to stimulate cell proliferation and differientation
  405. Density-Dependent Inhibition
    the phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact wiht one another
  406. Anchorage Dependence
    the requirement that a cell must be attached to a substratum in order to divide
  407. Benign Tumor
    a mass of abnormal cells that remains at the site of its origin
  408. Malignant Tumor
    a cancerous tumr that is incasice enough to impair the functions of one or more organs
  409. Metastasis
    the spread of cancer cells to locations distant from their original site
  410. Heredity
    the transmission of traits from one generation to the next
  411. Variation
    differences between members of the same species
  412. Genetics
    the scientific study of hereditary and hereditary variation
  413. Genes
    a discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses)
  414. Gametes
    • a haploid reproductive cell suchas an egg or sperm
    • gametes unite during sexual reproduction to produce a diploid zygote
  415. Asexual Reproduction
    the generation of offspring froma single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the organism into two or more parts) in most cases, the offspring are genetically identical to the parent
  416. Clone
    • (1) a lineage of genetically identical individuals or cells
    • (2) in popular usage, a single individual organism that is genetically identical to another individual
    • (3) as a verb, to make one or more genetic replicas of an individual or cell
  417. Sexual Reproduction
    a type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the parents
  418. Life Cycle
    the generation-to-generation seqeunce of stages in the reproductive history of an organism
  419. Karyotype
    a display of the chromosome pairs of a cell arranged by size and shape
  420. Homologous Chromosomes
    • a pair of chromosomes of the same lenth, centriomer position, and staining pattern that possess genes for the same characters at corresponding loci
    • one homologous chromosome is inherited from the organism's father, the other from the mother
    • also called homologs, or homologous pair
  421. Sex Chromosomes
    a chromosome responsible for determining the sex of an individual
  422. Autosomes
    a chromosome that is not dierectly involved in determining sex; not a sex chromosomes
  423. Diploid Cell
    a cell containing two sets of chromosomes (2n), one set inhherited from each parent
  424. Haploid Cells
    a cell containing only one set of chromosomes (n)
  425. Ferilization
    • (1) the union of haploid gametes to pruduce a diploid zygote
    • (2) the addition of mineral nutrients to the soil
  426. Zygote
    the diploid product of the union of haploid gametes during fertilization; a fertilized egg
  427. Alternation of Generations
    a life cycle in which there is both a multicellular diploud form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants and some algae
  428. Sporophyte
    • in organisms (plants and some algae) that have alternation of generations, the multicellular diploid form that results from the union of gametes
    • the sporophyte produces haploid spores by meiosis that develop into gametophytes
  429. Spores
    • (1) in the life cycle of a plant or alga undergoing alternation of generations, a haploid cell produced in the sporophyte by meiosis
    • a spore can be divided by mitosis to develop into a multicellular hapoliod individual, the gametphyte, without fusing with another cell
    • (2) in fungi, a haploid cell, produced either sexually or asexually, that produces a myceliu, after germination
  430. Gametophyte
    • in organisms (plants and some algae) that have alternation of generations, the multicellular haploid form that produces haploid gamets bhy mitosis
    • the haploid gametes unit and develop into sporophytes
  431. Meiosis I
    the first division of a two stage process of cell division in sexually repoducing organisms that results in cells with half the number of chromosome sets as the original cell
  432. Meiosis II
    the second division of a two stage process of cell division ins exually reproducing organisms that results in cells with half the number of chromosome sets as the original cell
  433. Synapsis
    the pairing and replication of homologous chromosomes during prophase 1 of meiosis
  434. Crossing Over
    the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis
  435. Chiasma
    the x-shaped, microscopically visible region where homologous nonsister chromatids have exchanged genetic material through crossing over during meiosis, the two homologs remaining associated due to sister chromatid cohesion
  436. Recombinant Chromosomes
    a chromosome created when crossing over combines the DNA from two parents into a single chromosome
  437. True-Breeding
    referring to plants that produces offspring of the same variety when they self-polinate
  438. Hybridization
    in genetics, the mating, or crossing, of two true-breeding varieties
  439. P Generation
    the parent individuals fromw hich offspring are derived in studies of inheritance, p stands for parental
  440. F1 Generation
    the first filial, or hybrid, offspring in a series of genetic crosses
  441. F2 Generation
    offspring resulting from interbreeding of the hybrid F1 generation
  442. Alleles
    any of the alternative versions of a gene that produce distingushable phenotypic effects
  443. Dominant Allele
    an allele that is fully expressed in the phenotype of a heterozygote
  444. Recessive Allele
    an allele whose phenotypic effect is not observed in a heterozygote
  445. Law of Segregation
    Mendel's first law, stating that the two alleles in a pair segregate (seperate) into different gametes during gamete formation
  446. Punnett Square
    a diagram used in the study of inheritance to show the predicted resolts of random fertilization in genetic crosses
  447. Homozygous
    having two identical alleles for a given gene
  448. Heterozygous
    having two different alleles for a given gene
  449. Phenotype
    the physical and physiolgoical traits of an organism, which are determined by its genetic makeup
  450. Genotype
    the genetic make up, or set of alleles, of an organism
  451. Testcross
    • breeding on organism of unkown genotype with a homozygous recessive individual to determine the unkown genotype
    • the ratio of phenotypes in the offspring reveals the unknown genotype
  452. Monohybrids
    • an organism that is heterozygous with respect to a single fene of interest
    • all the offspring from a cross between parents homozygous for different alleles are monohybrids
    • for example, parents of genotypes AA and aa produce a monohybrid of genotype Aa
  453. Dihybrids
    • an organism that is heterozygous with respect to two genes of interest
    • all the offspring from a cross between parents doubly homozygous for different alleles are dihybrids
    • for example, parents of genotypes AABB and aabb produce a dihybrid of genotypes AaBb
  454. Law of Independent Assortment
    Mendel's second law, stating that each pair of alleles segregates, or assorts, indepependently of each other pair during gamete formationl applies when genes for two characters are located on different pairs of homologous chromosomes
  455. Complete Dominance
    the situation in which phenotypes of the heterozygote and dominant homozygote are indistinguishable
  456. Incomplete Dominance
    the situation in which the phenotype of heterozygous is intermediate between the phenotypes of individuals homozygous for either allele
  457. Codominance
    the situation in which the pheotypes of both allels are exhibited in the heterozygote because both allels affect the phenotype in seperate, distinguishable ways
  458. Tay-Sachs Disease
    a human genetic disease caused by a recessive allele for a dysfunctional enzyme, leading to accumalition of certain lipids in the brain, seizures, blindness, and degeneration of motor and mental performance usually become manifest a few months after birth, followed by death within a few years
  459. Pleiotropy
    the ability of a single gene to have multiple effects
  460. Epistasis
    a type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited
  461. Quantitative Characters
    a heritable feature that varies continusously over a range rathen than in an either-or fashion
  462. Polygenic Inheritance
    an additive effect of two or more genes on a single phenotypic character
  463. Norm of Reaction
    the range of phenotypes produced by a single genotype, due to environmental influences
  464. Multifactorial
    referring to a phenotypic character that is influenced by multiple genes and environmental factors
  465. Pedigree
    a diagram of a family tree showing the occurrence of heritable characters in parents and offspring over multiple generations
  466. Cystic Fibrosis
    a human genetic disorder caused by a recessive allele for a chloride channel protein; characterized by an ecessive secretion of mucus and consequent vulnerabilty to infection; fatal if untreatedd
  467. Sickle-Cell Disease
    a human genetic disease by a recessive allele that results in the substitution of a single amino acid in a globin polypeptide that is part of the homoglobin protein; characterized by deformed red blood cells (due to protein aggregation) that can lead to numerous symptoms
  468. Huntington's Disease
    a human genetic disease caused bya dominant allele, characterized by uncontrollable body movements and degeneration of the nervous systemm; usually fatal 10 to 20 years after onset of symptoms
  469. Amniocentesis
    a technique of prenatal diagnosis in which amniotic fluid, obtained by aspiration from a needle inserted into the uterus, is analyzed to detect certain genetic and congenital defects in the fetus
  470. Chorionic Villus Sampling (CVS)
    a technique of prenatal diagnosis in which a small sample of the fetal portion of the placenta is removed and analyzed to detect certain genetic and congenital defects in the fetus
  471. Transformation
    • (1) the conversion of a normal animal cell to a cancerous cell
    • (2) a change in genotype and phenotype due to the assimilation of external DNA bya cell
  472. Bacteriophages
    a virus that infects bacteria; also called a phage
  473. Phages
    a virus that infects bacterial also called bateriophage
  474. Double Helix
    the form of native DNA, refering to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape
  475. Semiconserative Model
    the type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand
  476. Origins of Replication
    site where the replication of a DNA molecule begins, consisting of a specific sequnece of nucleotides
  477. Replication Fork
    a y-shaped region on a replicating molecule where the parental strands are being unwound and new strands are growing
  478. Helicases
    an enzyme that untwists the double helix of DNA at the replication forks, seperating the two strands and making them available as tmeplate strands
  479. Single-Strand Binding Proteins
    a protein that binds to the unpaired DNA strands during DNA replication, them and holding them apart while they serve as template for the synthesis of complementary strands of DNA
  480. Topoisomerase
    • a prtotein that breaks, swivels, and rejoins DNA strands
    • during DNA repliation, topoisomerase helps to relieve strain in the double heliz ahead of the replication fork
  481. Primase
    an enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template
  482. Primer
    a short stretch of RNA with a free 3' end, bound by complementary base pairing to the template strand, that is elongated with DNA nucleotides during DNA replication
  483. DNA Polymerases
    • an enzyme that catalyzes the elongation of new DNA (for example, at a replication fork) by the addition of nucleotides to the 3' end of an existing chain
    • there are several different DNA polymerases; DNA polymerase III and DNA polymerase I play major roles in DNA replication in prokaryotes
  484. Leading Strand
    the new complimentary DNA strand synthesized continously along the template strand toward the replication fork in the madatory 5' to 3' direction
  485. Lagging Strand
    a discontinusously synthesized DNA strand that elongates by means of okazaki fragments, each synthesized in 5' to 3'direction away from the replication fork
  486. Okazaki Fragments
    a short segment of DNA synthesized away from the replication fork on a template strand during DNA replication, many of which are joined together to make up the lagging strand of newly synthesized DNA
  487. DNA Ligase
    a linking enzyme essential for DNA replication; catalyzes the covalent bonding of 3' end of one DNA frazgment (such as Okazaki fragment) to the 5' end of another DNA fragment (such as a growing DNA chain)
  488. Mismatch Repair
    the cellular process that uses specific enzymes to remove and replace incorrectly paried nucleotides
  489. Nuclease
    an enzyme that cuts DNA or RNA, either removing one or few bases or hydrolyzing the DNA or RNA completely into its component nucleotides
  490. Nucleotide Excision Repair
    a repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide
  491. Telomers
    • the tandemly repeptitive DNA at the end of a eukaryotic chromosome's DNA
    • molecule that protects the organism's genes from being eroded during successive rounds of replication
  492. Telomerase
    an enzyme that catlyzes the lengthening of telomers in eukaryotic germ cells
  493. Nucleiod
    a dense region of DNA in a prokaryotic cell
  494. Heterochromatin
    eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed
  495. Euchromatin
    the less condensed form of eukaryotic chromatin that is available for transcription
  496. Gene Expression
    the process by which the synthesis of proteins or, in some cases, just RNAs
  497. Transcription
    teh synthesis of RNA using a DNA template
  498. Messenger RNA (mRNA)
    a type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein
  499. Translation
    • the synthesis of a polypeptide using the genetic information encoded in an mRNA molecule
    • there is a change of "language" from nucleotides to aminoa cids
  500. Primary Transcript
    an initial RNA transcript; also called pre-mRNA when transcribed froma protein-coding gene
  501. Triplet Code
    a set of three-nucleotide-long words that specify the amino acids for polypeptide chainse
  502. Template Strand
    the DNA strand that provides the pattern, or template for odering the sequence of nucleotides in an RNA transcript
  503. Codons
    a three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code
  504. Reading Frame
    ona mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis
  505. RNA Polymerase
    an enzyme that links ribonucleotides into a growing chain during transcription
  506. Promotor
    a specific nucleotide sequence in DNA that binds RNA polymerase, positioning to start transcribing RNA at the appropriate place
  507. Terminator
    in bacteria, a sequence of nucleotides in DNA that marks the end of gene and signals RNA polymerase to release the newly made RNA molecule and detach from the DNA
  508. Transcription Unit
    a region of DN A that is transcribed into an RNA molecule
  509. Transcription Factors
    a regulatory protein that binds to DNA and affects the transcription of specific genes
  510. Transcription Initiation Complex
    the completed assembly of transcription factors and RNA polymerase bound to a promoter
  511. TATA Box
    a DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex
  512. Poly-A Tail
    a sequence of 50 to 250 adenine nucleotides added onto the 3' end of a pre mRNA molecule
  513. RNA Splicing
    after synthesis of a eukaryotic primary RNA transcript, the removal of portions (introns) of the transcript that will not be included in the mRNA
  514. Introns
    a noncoding,intervening sequence within a primary transcript that is removed from the transcript during RNA processing; also refers to the region of DNA from which this sequence was transcribed
  515. Exons
    a sequence within a primary transcript which remans in the RNA after RNA processing; also refers to region of DNA from which this sequence was transcribed
  516. Spliceosome
    a large complex made up of proteins and RNA molceules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons
  517. Ribozymes
    an RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing
  518. Alternative RNA Splicing
    a type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns
  519. Domains
    • (1)a taxonomic category above the kingdom level
    • the three domains are archaea, bacteria, and eukarya
    • (2) an independently folding part of a protein
  520. Transfer RNA (tRNA)
    an RNA molecule that dunctions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA
  521. Anticodon
    a nucleotide triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule
  522. Aminoacyl-tRNA Synthetases
    an enzyme that joins each amino acid to the appropriate tRNA
  523. Wobble
    flexibility in base pairing rules in which the nucleotide at the 5' end of a tRNA anitcodon can form hydrogen bonds with more than one kind of base in the third position (3'end) of a codon
  524. Ribosomal RNAs rRNAs
    the most abundant type of RNA, which together with proteins makes up ribosomes
  525. P Site
    • one of ribosome's three binding sites for tRNA during translatin
    • the p site holds the tRNA carrying the groqing polypeptide chain
  526. A Site
    • one of the ribosome's three binding sites for tRNA during translation
    • the a site holds the tRNA carrying the next amino acid to be added to the polypeptide chain (A stands foe aminoacyl tRNA)
  527. E Site
    • one of ribosmal's htree bidning sites for tRNA durinf translation
    • the E site is the place where discharged tRNAs leave the ribosome
  528. Polyribosomes (Polysomes)
    a group of several ribosomes attached to, and translating, the same messenger RNA molecule
  529. Signal Peptide
    a sequence of about 20 amino acids at or near the leading (amino) end of a polypeptide that targets it to the endoplasmic reticulum or other organelles in a eukaryotic cell
  530. Signal-Recognition Particle (SRP)
    a protein RNA-complex that recognizes a signal peptide as it emerges from a ribosome and helps direct the ribosome to en ER by binding to a receptor protein on the ER
  531. Mutations
    • a change in the nucleotide sequence of an organism's DNA, ultimately creating genetic diversity
    • mutations also can occur in the DNA or RNA of a virus
  532. Point Mutations
    a change in a gene at a single nucleotide pair
  533. Base-Pair Substitution
    a type of point mutation; the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides
  534. Missense Mutations
    a base-pair substitution that results in a codon that codes for a different amino acid
  535. Insertions
    a mutation involving the addition of one or more nucleotide pairs ot a gene
  536. Deletions
    • (1) deficiency in a chromosome resulting from the loss of a fragment through breakage
    • (2) a mutational loss of one or more nucleotide pairs from a gene
  537. Frameshift Mutation
    a mutation occuring when the number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the subsequent nucleotides into codons
  538. Mutagens
    a chemical or physical agent that interacts with DNA and causes a mutation

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