Quiz 6, BICH 410 (MWF3-3:50), Friday, Dec. 4, 1998

Clearly circle the letter corresponding to your answer for each problem. There are six problems, four of which count 3 points, and two for 4 points. No partial credit given for multiple-choice questions.
gas constant R 8.315 J/mole-K; Faraday constant F 96.5 kJ/mole-volt

1. Oxaloacetate uniformly labeled with 14C (i.e., with equal amounts of 14C in each of its carbon atoms) is condensed with unlabeled acetyl-CoA. After a single pass through the citric acid cycle back to oxaloacetate, what fraction of the original radioactivity will be found in the oxaloacetate?
Answer: C


2. (4 pts) Which of the following is a mobile component of the electron transport chain?
Answer: B


3. A metabolic function of the pentose phosphate pathway is:
Answer: D


4. Entry of acetyl-CoA into the citric acid cycle (via pyruvate dehydrogenase) is decreased when:
Answer: A


5. (4 pts) The standard reduction potentials (Eo') for the following half reactions are given.
fumarate + 2H+ + 2e- <-> succinate; Eo' = +0.031 volt
FAD + 2H+ + 2e- <-> FADH2; Eo' = -0.219 volt
If you mixed succinate, fumarate, FAD, and FADH2 together, all at 1 M concentrations and in the presence of succinate dehydrogenase, which of the following would happen initially?
Answer: D; Summed reaction written as reduction of fumarate would have deltaEo' = +0.031 + 0.219 v = +0.25 v; a positive value for deltaEo' means that the reaction is thermodynamically favorable, so fumarate would be reduced and FADH2 would be oxidized under standard conditions (1 M, each, of reactants and products)


6. The conversion of 1 mole of pyruvate to 3 moles of CO2 via the citric acid cycle also yields ____ moles of NADH, ____ moles of FADH2, and ____ moles of ATP (or GTP).
Answer: E; note that starting with pyruvate, you must consider also the pyruvate dehydrogenase reaction, in which one mole of NADH is generated.