Biol 211, Fall 2008
Exam #2
Name ____________________
Section 1. Questions in this section can be answered with one or a few words.
For the following definitions, provide the correct term.
1. Form of chemical reaction where electrons are removed from one molecule by another molecule. (1
pt)
[redox reaction]
2. A complex of proteins that directly produces ATP by using the concentration gradient of H+. (1 pt)
[ATP synthase (electron transport chain ok)]
3. Type of energy that comes from the structural arrangement of molecules. (1 pt)
[chemical energy or potential energy]
4. An organism that must get its carbon compounds by eating other organisms. (1 pt)
[heterotroph or consumer]
5. Type of chemical bond where one or more electrons are shared between two elements in order to fill
their outer electron shells. (1 pt)
[covalent bond]
6. Type of protein used to lower the activation energy required for many chemical reactions. (1 pt)
[enzymes or catalysts]
7. Term for the harnessing of a concentration gradient to do cellular work (1 pt)
[chemiosmosis]
8. Organism that must live in an environment without oxygen. (1 pt)
[obligate anaerobe]
Answer the following questions.
9. During which stage of cellular respiration is carbon dioxide produced? (1 pt)
[Citric Acid cycle (also pre-CAC]
10. List two functions of accessory pigments (1 pt)
[broaden spectrum of light used for PS, sunscreen, coloration]
11. What is the function of Coenzyme A?(1 pt)
[makes acetic acid more reactive – ready to enter the citric acid cycle]
12. List one piece of evidence that supports the Endosymbiosis Theory. (1 pt)
[similar size to bacteria, own ribosomes, similar reproduction, ETC’s similar to bacteria, Circular DNA
with few proteins, molecular similarities]
13. If ΔG is greater than zero, than the chemical reaction will be (exergonic/endergonic)? (1 pt)
[endergonic]
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Biol 211, Fall 2008
Exam #2
Name ____________________
14. List one enzyme that participates in glycolysis and briefly describe its function. (1.5 pt)
[many correct answers]
15. What is the function of a chaperonin? (1 pt)
[place for proteins to fold]
16. How does ATP perform cellular work? (1 pt)
[phosphorylates molecules]
17. Why do electrons from FADH2 generate fewer ATP in the electron transport chain in mitochondria
than electrons from NADH? (1 pt)
[deposits them further down on the ETC, so fewer H+ come across]
Section 2. Short Answer.
18. Provide a concise definition for each that will clearly distinguish between the following pairs of
terms. Be sure to include how the two terms are related to one another. (2 pts each):
a) entropy / enthalphy
[both involved in determining whether or not a reaction will be spontaneous. Entropy is the measure of
the amount of disorder in a group of molecules. Enthalpy is a measure of the difference in energy
between reactants and products.
b) oxidative phosphorylation / substrate-level phosphorylation
[Both processes produce ATP. OP produces ATP through use of an electron transport chain where
oxygen is the final electron acceptor. Substrate-level phosphorylation is the production of ATP by
transferring a phosphate group from a substrate to ADP.]
Answer the following questions.
19. a) What role does pyruvate dehydrogenase play in cellular respiration? (2 pts)
[enzyme where pyruvate transformed into Coenzyme A)
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Biol 211, Fall 2008
Exam #2
Name ____________________
b) What are two ways that pyruvate dehydrogenase can be regulated? (2 pts)
[high ATP inhibits, low ADP stimulates, also needs coenzyme]
20. The relationship between structure and function is a major theme in biology. Please discuss this
theme in relation to enzymes. (3 pts)
[Many ways of addressing this. To get full credit you must discuss induced fit of substrate in active site.
Also how if denatured, enzyme loses its structure, so substrate will not longer fit properly at the active
site, so it loses its function.]
21. Early research into the mechanisms of photosynthesis hypothesized that O2 is produced by splitting
CO2. Describe one experiment that supported the idea that O2 is produced by the splitting of water and
not from CO2. (2 pts)
[From assigned reading in textbook. Research with photosynthetic bacteria that did not produce O2,
splitting H2S instead, hypothesizing that all photosynthesizing organisms need a H source for electrons,
and that would be H2O. Another study used an isotope of oxygen to trace its path and discovered that it
came from H2O.]
22. What would happen, in terms of a cell’s ability to do photosynthesis, if a mutation occurred that
caused the primary electron acceptor in the water-splitting photosystem (PS2) to become a stronger
electron acceptor than the chlorophyll a in the NADPH-producing photosystem (PS1)? Be specific. (3
pts)
[Electrons would no longer be “pulled” down the ETC. So no H+ would be pumped across the ETC, so
no gradient, so no ATP produced. No ATP to go into the Calvin cycle, so no production of G3P. Also
no NADPH produced to go into the Calvin cycle.]
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Biol 211, Fall 2008
Exam #2
Name ____________________
23. a) All organisms need ATP to do cellular work. Prior to 2.7 bya there was no free oxygen on the
planet, yet organisms have been around since 3.6 bya. How did these early organisms (pre-2.7bya)
generate ATP? (2 pts)
[by using anaerobic respiration or fermentation, which do not require oxygen].
b) What evolutionary changes were made possible by the rise in atmospheric oxygen after 2.7 bya
and how did organisms benefit (or not benefit) from these changes? (2 pts)
[aerobic respiration was made possible. More ATP created, so more ability to grow large. Other
organisms went extinct]
24. a) What is feedback inhibition? (2 pts)
[Feedback from metabolic pathway, in the form of a buildup of products that then act as an inhibitor
to the pathway.]
b) Provide a specific example of feedback inhibition from the material we have covered in class. (2
pts)
[Several possible examples. Feedback on isoleucine synthesis (fig. 8.22), where isoleucine binds with an
enzyme early in the process at an allosteric site. Phosphofructokinase inhibited by ATP. Pyruvate
dyhydrogenase inhibited by ATP. Enzyme that converts acetyl-CoA to citrate inhibited by ATP.
Enzyme tha converts isocitrate to a-ketogluterate inhibited by NADH.
25. a) What is the function of rubisco? (2 pts)
[Attaches CO2 to ribulose bisphosphate in the calvin cycle]
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Biol 211, Fall 2008
Exam #2
Name ____________________
b) Why would it be the most abundant enzyme on the planet? (1.5 pts)
[Many possible answers]
Bonus Question (2pts)
Answer only one of the question below.
1. You are a researcher studying two different species of crabs. One species of crab lives in water that
is at a much lower temperature than where the other crab lives. What is one difference you might expect
to see in the structure of the plasma membrane between the two crab species?
[In order to prevent the phospholipids from solidifying, the crab that lives in the lower temperature may
have cholesterol or unsaturated hydrocarbons in its plasma membrane]
2. What would be the effect on a cell if the endoplasmic reticulum stop synthesizing hydrolytic enzymes?
[No enzymes available to be contained in a lysosome. Lysosomes would be unable to perform their
functions, which includes nutrient digestion, destruction of cell invaders (bacteria) and recycling
damaged organelles]
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