biologypcat.txt

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ju08
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25240
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biologypcat.txt
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2010-07-02 21:42:15
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Biology PCAT
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Biology PCAT
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  1. What are carbohydrates?
    Organic compounds composed of the elements carbon, hydrogen, and oxygen in a 1:2:1 ratio. They are used for energy storage (i.e. glucose and glycogen in animals; starch in plants) and structural molecules (i.e. cellulose).
  2. Name four common monosaccharides, one disaccharide, and two polysaccharides.
    • monosaccharides: Fructose, Glucose, Galactose, Mannose
    • disaccharide: glucose -> maltose
    • polysaccharides: Glycogen, starch, cellulose
  3. What are Lipids (fats and oils)?
    Organic molecules composed of 3 fatty acid molecules and 1 glycerol backbone. Lipids do not form polymers. They are the cheif mean of food storage in animals. They also provide insulation and protection against injury (i.e. adipose tissue).
  4. What are some lipid derivatives?
    -phospholipids: contain glycerol, 2 fatty acids, a phosphate group, and nitrogen-containing alcohol. e.g. lecithin (a major constituent of cell membranes)

    -waxes: are esters of fatty acids and monohydroxylic alcohols.

    -Steroids: have three fused cyclohexane rings and one fused cyclopentane ring. They include cholesterol, the sex hormones testosterone and estrogen, and corticosteroids.

    -Cartenoids: are the pigments that produce red, yellow, orange, and brown colors in plants and animals. Two subgroupds are the carotenes and the xanthophylls.

    -porphyrins: also called tetrapyrroles, contain four joined pyrrole rings. They are often complexed with a metal.
  5. What are amino acids?
    They are joined by peptide bonds through dehydration reactions.

    ex. arginine, lysine, histidine
  6. What are proteins?
    They are composed of C,H,O, and N but may also contain P and S. They are polymers of amino acids and are therefore also reffered to as polypeptides.
  7. Name the four protein structures.
    • -primary structure: sequence of amino acids
    • -secondary structure: based on hydrogen bonding between adjacent amino acids and results in beta-pleated sheets or alpha-helices
    • -tertiary structure: 3D structure based on R-group interactions between adjacent amino acids.
    • -quaternary structure: the interaction and joining of two or more independent polypeptide chains.
  8. What are simple proteins?
    Proteins composed entirely of amino acids.
  9. What are albumins and globulins?
    Functional proteins that act as carriers or enzymes.
  10. What are Scleroproteins?
    These are fibrous in nature and act as structural proteins i.e. collagen
  11. What are conjugated proteins?
    These contain simple protein portion plus at least one nonprotein fraction.
  12. What are Lipoproteins?
    Proteins bound to lipids.
  13. What are mucoproteins?
    Proteins bound to carbohydrates.
  14. What are chromoproteins?
    Proteins bound to pigment molecules.
  15. What are metalloproteins?
    Proteins complexed to a metal ion.
  16. What are nucleoproteins?
    Proteins containing histone or protamine (nuclear protein) bound to nucleic acids.
  17. What are some protein functions?
    • -hormones: proteins that function as chemical messengers secreted into the circulation. Insulin and ACTH are protein hormones.
    • -Enzymes: Biological catalysts that act by increasing the rate of chemical reactions important for biological functions (i.e. amylase, lipase, and ATPase)
    • -Structural proteins: contribute to the physical support of a cell or tissue. They may be extra or intracellular.
    • -Transport proteins: carriers of important materials. For example, hemoglobin carries oxygen in the circulation, and the cytochromes carry electrons during cellular respiration.
    • -Antibodies: these bind to forgein particles (antigens), including disease causing organisms, that have entered the body.
  18. What is competitive inhibition?
    If a similar molecule is present in a concentration comparable to the concentration of the substrate, it will compete with the substrate for bonding sites on the enzyme and interfere with enzyme activity. The enzyme is inhibited by the inactive substrate, or competitor.
  19. What is Noncompetitive inibition?
    A noncompetitive inhibitor is a substance that forms strong covalent bonds with an enzyme and consequently may not be displaced by the addition of excess substrate. A noncompetitive inhibitor may be bonded at, near, or remote from the active site.

    When the inihibition takes place at a site other than the active site, this is called allosteric inhibition. (Allosteric means "other site" or "other structure") The inhibition of an inhibitor at an allosteric site changes the structure of the enzymes so the active site also changes.
  20. Give some examples of enzyme activity.
    Lactase hydrolyzes lactose to the monosaccharides glucose and galactose.

    Proteases degrade proteins to amino acids

    Lipases break down lipids to fatty acids and glycerol
  21. What is a cofactor?
    Nonprotein molecules such as: metal cations such as Zn2+ or Fe2+ or small organic groups called coenzymes bind to enzymes to activate them.

    Cofactors that bind to enzymes by strong covalent bonds are called prosthetic groups.
  22. What is the Cell Theory?
    • -All living things are composed of cells.
    • -The cell if the basic unit of life.
    • -The chemical reactions of life take place insde the cell.
    • -Cells arise only from pre-existing cells.
    • -Cells carry genetic information in the form of DNA. This genetica material is passed from parent to daughter cell.
  23. Cell structure
  24. Describe the cell membrane (plasma membrane) according to the fluid mosaic model.
    The cell membrane consists of a phospholipid bilayer with proteins embedded throughout.

    The long, nonpolar, hydrophobic, "fatty" chains of carbon and hydrogen face each other, with the phosphorous containing, polar, hydrophyilic heads facing outward. The hydrophyilic heads face the watery regions inside and outside the cell, while the hydrophobic tails face each other in a water-free region.
  25. How do things crosss the cell membrane?
    The membrane is permeable to small nonpolar hydrophobic molecules such as O2 and small polar hydrophyilic molecules such as H2O.

    However, charged ions and larger charged molecules cross the membrane witht the assistance of carrier proteins.
  26. Cytosol vs Cytoplasm.
    The cytoplasm contains many organelles and other cell components suspended in a semifluid medium, the cytosol. Transport within the cytoplasm occurs by cyclosis (streaming movement within the cell).
  27. What is the function of a nucleus?
    It controls the activities of the cell, including cell division. It is surrounded by the nuclear membrane. It contains DNA, and it also houses the nucleolus, which is where ribosomal RNA (rRNA) (ribosome synthesis) occurs.
  28. What is the function of a ribosome?
    They are sites of protein production. Free ribosomes are found in the cytoplasm, whereas bound ribosomes line the outer membrane of the endoplasmic reticulum.
  29. What is the function of the endoplasmic reticulum? (smooth and rough er)
    The endoplasmic reticulum (ER): network of membraneous sac and tube; active in membrane synthesis and other synthetic and metabolic processes. It is also envolved in the transport of materials throughout the cell, particularly those destined to be secreted by the cell.
  30. What is the function of the golgi apparatus?
    It recieves vesicles and thei contents from the smooth ER, modifies them, repackages them into vesicles, and distributes them to the cell surface by exocytosis.
  31. What is the function of the mitochondria?
    Organelle where aerobic respiration occurs and most ATP is generated. It is bounded by an outer and inner phospholipid bilayer.
  32. What is the function of a vacuole and vesicle?
    Vacuoles and vesicles are membrane bound sacs involved in the transport and storage of materials that are ingested, secreted, processed, or digested by the cell. Vacuoles are larger than vesicles and are more likely to be found in plant than in animal cells.
  33. What is the function of centrioles?
    They are composed of microtubules and are involved in spindle organization during cell division and are not bound by a membrane. Animal cells usually have a pair of centrioles that are are oriented in right angles to each other and lie in a region called the centrosome. Plant cells do not contain centrioles.
  34. What is the function of the cytoskeleton?
    It supports the cell, maintains its shape, and functions in cell motility. It is composed of microtubules, microfilaments, and intermediate filaments.

    Microtubules are hollow rods made up of polymerized tubulin that radiate throughout the cell and provide it with support. They provide a framework for organelle movement within the cell. Cilia and flagella are specialized arrangements of microtubules that extend from certain cells and are involved in cell motility and cytoplasmic movement.

    Microfilaments are solid rods of actin, which are important in cell movement as well as support. Muscle contraction, for example, is based on the interaction of action with myosin. They move materials across the plasma membrane, for instance, in the contraction phase of cell divison and in amoeboid movement.
  35. What is the function of a lysosome?
    They are membrane-bound vesicles that contain hydrolitic enzymes involved in intracellular digestion. Lysosomes break down material ingested by the cell. An injured or dying tissue may "commit suicide" by rupturing the lysosome membrane and releasing its hydrolytic enzymes; this process is called autolysis.
  36. Organelles: Animal cell vs plant cell
    • In animal but not plant cells:
    • Lysosomes
    • Centrosomes, with centrioles
    • flagella (but found in some plant sperm)

    • In plant but not animal cells:
    • Chloroplasts
    • Central vacuole
    • cell wall
    • plasmodesmata: channels through cell walls that connect the cytoplasm of adjacent cells
  37. Differentiate between active and passive transport.
    • PASSIVE TRANSPORT: no energy required
    • -simple diffusion (no energy required): net movement of dissolved particles down their concentration gradients (higher -> lower). i.e. osmosis (H2O lower->higher solute concentration)
    • -Facilitated diffusion (no energy): net movement of dissolved particles down their concentration gradient through special channels (carrier proteins) in the cell membrane.

    • ACTIVE TRANSPORT: the net movement of dissolved particles against their concentration gradient with the help of transport proteins. Energy is required.
    • Carrier molecules:
    • -Energy independent carriers:facilitate the movement of compounds along a concentration gradient.
    • -symporters:move two or more ions or molecules
    • -antiporters:exchange one or more ions (or molecules) for another ion molecule
    • -pumps:energy-independent carriers (require ATP); e.g. sodium postassium pump
  38. What is plasmolysis?
    In a hypertonic solution, the water flows out of the cell, causing it to shrivel to death.
  39. What is lysis?
    In a hypotonic solution, water will flow into the cell, causing it to burst.
  40. Intracellular circulation:
    • -Brownian movement: KE spreads small suspended particles throughout the cytoplasm of the cell
    • -Cyclosis or streaming: the circular motion of cytoplasm around the cell transports molecules
    • -endoplasmic reticulum:this provides channels throughout the cytoplasm and provides a direct continuous passageway from the plasma membrane to the nuclear membrane.
  41. Prokaryotes vs eukaryotes
    • Organiation of genetic material:
    • Prokaryotes: DNA is located in the nucleoid (NOT enclosed by a membrane)
    • eukaryotes: DNA is located in the nucleus (enclose by nuclear envelope)

    • Site of cellular respiration:
    • Prokaryotes: cellular respiration occurs directly at the cell membrane
    • Eukaryotes: cellular respirtion occurs in the mitochondria

    • Presence of membrane-bound organelles:
    • Prokaryotes: no membrane bound organelles
    • Eukaryotes: contains membrane bound organelles such as the nucleus, lysosome, vesicles, mitochondria, and endoplasmic reticulum.

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