Biology test #3

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zzto
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117509
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Biology test #3
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2011-11-18 00:22:56
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Biology quiz answers
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Study questions for chapters 9-12ish
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  1. A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?
    Catabolic processes are activated that generate ATP.
  2. Following
    glycolysis and the Krebs cycle and before the electron transport chain and
    oxidative phosphorylation, the carbon skeleton of glucose has been broken down
    to CO2. Most of the energy from the original glucose at that point is still in the form of ________.
    NADH
  3. What electron carrier(s) function in the Krebs cycle?
    both NAD+ and FAD
  4. When one of the eight Krebs cycle intermediates is added to the respiration medium of living cells, like yeast, what happens to the rates of ATP and carbon
    dioxide production? (Assume energy levels are low.)
    • The rates of ATP production and
    • carbon dioxide production both increase.
  5. The process of joining the hydrolysis of ATP generating ADP + Pi to an endergonic reaction to provide the necessary energy to drive the
    energy requiring reaction to the formation of products is known as:
    energetic coupling
  6. Why are fermentation reactions important for cells?
    They regenerate NAD+ so that glycolysis can continue.
  7. Consider the reaction CH4 (methane) plus O2 yields CO2 plus H2O plus energy. Which of the following is true?
    • Methane acts as an electron
    • donor.
  8. Which of the following compounds inhibits pyruvate dehydrogenase via feedback inhibition
    NADH
  9. Under which conditions will the Krebs cycle be
    activated?
    high levels of NAD+
  10. If one molecule of glucose is taken through the entire glycolysis pathway, and ONLY the glycolysis pathway, what are the NET products that store the remaining
    chemical free energy?
    2 ATPs, 2 NADHs, and 2 pyruvates
  11. The chemiosmotic hypothesis is an important concept in our understanding of cellular metabolism in general because _____.
    it explains how ATP is synthesized by a proton motive force
  12. The electron transport chain _____.
    is a series of redox reactions
  13. When an electron is excited by the absorption of light
    energy, and then “falls” back to the ground state without transferring the energy to another molecule, the absorbed energy is released as light and heat.
    This light energy is specifically called__________. When the energy is transferred to another pigment molecule in the antennae complex exciting that
    pigment’s electrons, the energy exchange is referred to as _____________.
    fluorescence; resonance
  14. If a proton ionophore, a molecule that forms an artificial channel allowing hydrogen ions to cross membranes, is inserted into the inner mitochondrial membrane, what happens to the concentration of ATP in a cell?
    ATP levels will decrease
  15. Van Niel's experiments with purple sulfur bacteria led to which of the following hypotheses?
    During plant photosynthesis, the oxygen gas released comes from water
  16. In autumn, the leaves of deciduous trees change colors. This is because the chlorophyll is degraded, and ________.
    the carotenoids and other pigments are still present in the leaves.
  17. Engelmann's experiment with Spyrogyra ( a
    filamentous algae) involved exposing these photosynthetic organisms to a prism, which divided sunlight into the individual components of the visible light spectrum. Aerobic bacteria grew best along the parts of the algae that were exposed to red and blue light. Why?
    • In these two areas photosynthesis
    • was occuring and oxygen was produced.
  18. What is the best evidence for the presence of two
    photosystems?
    • The combination of far red and red light is much more effective at stimulating photosynthesis than either
    • color alone; i.e. the enhancement effect.
  19. Howare the light-dependent and light-independent reactions of photosynthesis related?
    The products of light-dependent reactions are used in light-independent reactions.
  20. How many cycles of Beta oxidation would a 12 – carbon fatty acid undergo?
    5
  21. Data suggest that rubisco (ribulose-1,5-bisphosphate
    carboxylase) makes up 10% of the total protein found in spinach leaves. Research elucidating the structure of rubisco shows that it has 8 active sites. Why, with 8 active sites, might there be such a large concentration of rubisco in plant matter?
    Rubisco is a very slow enzyme; what it lacks in speed, it makes up in numbers.
  22. Stomata, openings in the leaf, are important to photosynthesis for
    entry of carbon dioxide that is used in the Calvin cycle.
  23. How does carbon fixation differ between C3 and C4 plants?
    • Rubisco is the primary enzyme that catalyzes carbon fixation in C3 plants, and phosphoenolpyruvate carboxylase can catalyze carbon fixation in C4
    • plants in addition to Rubisco.
  24. CAM plants function using crassulacean acid metabolism. Like C4 plants, CAM plants provide a preparatory step for the Calvin cycle. CAM plants are found in hot, dry environments; to prevent dessication, they keep their stomata closed during the day. They take in carbon dioxide at night while stomata are open. To increase the concentration of carbon dioxide available to the enzyme rubisco
    and minimize the degree of photorespiration, the CAM plants carboxylate
    ________.
    small 3 carbon compounds into organic acids
  25. In eukaryotic cells, chromosomes are composed of _____.
    DNA and proteins
  26. What is the final result of mitosis?
    genetically identical 2n somatic cells
  27. The first gap in the cell cycle (G1) corresponds to _____.
    normal growth and cell function
  28. Metaphase occurs prior to the splitting of centromeres.
    It is characterized by _____.
    aligning of chromosomes on the equator
  29. Most of the enzymes of the Calvin cycle also function in other metabolic pathways. This should not be a surprising finding, because ________.
    there is a close relationship between carbohydrate synthesis and metabolic breakdown.
  30. Some cells have several nuclei per cell. How could such
    multinucleated cells be explained?
    The cell underwent repeated mitosis, but cytokinesis did not occur.
  31. When a sperm and egg combine, the resulting embryo has
    _____.
    • half of the mother's genetic information and
    • half of the father's
  32. Which of the following statements best describes a phase that occurs in meiosis II?
    Sister chromatids separate and begin moving to opposite sides of the cell.
  33. Crossing over occurs _____.
    between chromatids of homologous chromosomes.
  34. An individual plant that exhibits self-fertilization can produce offspring different from itself primarily as a result of _____.
    • B. crossing over
    • resutling in genetic sequence exchange between chromosomes
    • C. random alignment of chromosomes upon the
    • metaphase plate
  35. Which of the following statements is the leading hypothesis to explain why many organisms reproduce sexually?
    • The offspring that result from sexual
    • reproduction are genetically variable, and some of them can fight off diseases and adapt to their environment
    • more easily than genetically identical offspring
  36. The cells that produce sperm in humans contain 46 chromosomes. If one of these
    cells undergoes meiosis to form sperm cells, and chromosomal nondisjunction occurs in chromosome 22 during meiosis II, what is the chromosome number in each of the resulting sperm cells?
    23, 23, 22 and 24
  37. Nondisjuction of chromosomes results in _______________.
    aneuploidy
  38. What is a major difference between meiosis II and mitosis?
    • Meiosis II takes place in a haploid cell, while
    • mitosis takes place in diploid cells.
  39. During meiosis, Sister chromatids separate during ________.
    anaphase II
  40. What is a major difference between mitosis and meiosis I?
    Sister chromatids separate in mitosis, and homologues separate in meiosis I
  41. If meiosis produces haploid cells, how is the diploid number restored for those
    organisms that spend most of their life cycle in the diploid state?
    fertilization
  42. The cells that produce sperm in humans contain 46 chromosomes. If one of these
    cells undergoes meiosis to form sperm cells, and chromosomal nondisjunction occurs in Chromosome 22 during meiosis I, what is the chromosome number in each of the resulting sperm?
    24; 24; 22; 22
  43. Nerve cells lose their ability to undergo mitosis.
    Instead, they are permanently stuck in _____.
    G0
  44. Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis?
    • Cyclin is degraded; the concentration of
    • cyclin-dependent kinase remains unchanged, but without cyclin, MPF is not formed.
  45. Regulatory proteins that serve to prevent a cell from entering the S phase under conditions of DNA damage are also known as _____.
    tumor suppressors
  46. For cells to divide more rapidly, increased production would likely be required of
    each of the following proteins except _____.
    p53
  47. The consequence of E2F inactivation is that _____.
    cells would be unable to enter S phase
  48. Many cancers are due to the failure of cells to properly regulate the _____ checkpoint during the cell cycle.
    G1
  49. Much of what is known about the function of cyclin and Cdk was learned by mutations in yeast. One yeast mutant is known as wee1. As its name implies, this yeast mutant never achieves full size. It divides continuously without allowing time
    for the cells to grow to their normal size. The defect is caused by inactivation of a gene that encodes a protein kinase. What might be a possible role for this kinase in normal wild-type yeast?
    • It may phosphorylate and inhibit the activity of
    • mitotic Cdk
  50. When p53 disassociates from mdm2 and is turned on, what is/are the possible outcome(s)?
    • -apoptosis
    • -DNA repair enzymes are activated

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