Exam 4 Fall 2006
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There are 31 questions in all. 1-18 are 2-point multiple choice questions, and 19-26 are 3-point multiple choice questions. Questions 27-31 are essays and problems worth 40 points.

1-6. Use these molecules. Not all molecules are used.

A.

B.

C.

D.

E.

F.

G.

H.

              1. the substrate for PFK-2                           2. the product of PFK-2

              3. the substrate for succinyl-CoA synthetase

              4. the product of UDP-glucose pyrophosphorylase

              5. the substrate for UDP-glucose pyrophosphorylase

              6. the product of succinate dehydrogenase

7-10. Use the complexes involved in electron transport: I, II, III, and IV
Answer with only one even if there is more than one correct answer.
A complex may be used more than once or not at all.

              7. requires cyt bH, cyt bL, and cyt c1                                   8. oxidizes succinate

              9. reduces Q                                      10. moves 1 H+ N → P for each e− it transfers

              11. The coenzyme in the pyruvate dehydrogenase (PDH) complex that is required for oxidizing FADH2 is (C) CoA; (F) FAD; (L) lipoate; (N) NAD+; (T) TPP.

              12. The part of ATP synthase that moves H+ from P to N is a/n
(A) His side chain on the β subunit; (B) Mg2+ co-factor required by the α subunit;
(C) Asp side chain on the c subunit; (D) Glu side chain on the γ subunit.

              13. The T conformation of an ATP synthase β subunit has                    affinity for ATP and is next converted into the         conformation.
(A) low, L ; (B) high, L; (C) low, O; (D) high, O.

              14. The PDH complex is more active when the concentration of                 is higher than the concentration of                   .
(A) ATP, AMP; (B) AcCoA, CoA-SH; (C) NADH, NAD+; (D) AMP, ATP.

15-16. Use the labels on this glycogen molecule.

              15. Which two letters show where glycogen synthase could add a residue?

              16. Which line of letters shows the product of a debranching enzyme?
(A) A-B-C-D-E-F-G-H-I-K- ;           (B) E-F-G-H-I-K-A-B-C-D- ;
(C) A-B-C-E-F-G-H-I-K-   ;               (D) E-F-G-H-I-K-A-B-C- .

              17. Glycerol-3-phosphate dehydrogenase is required to move            from NADH produced during           into                .
(A) electrons, glycolysis, electron transport; (B) protons, glycolysis, ATP synthase; (C) electrons, citric acid cycle, P side; (D) protons, citric acid cycle, ATP synthase.

              18. Each ATP synthesized during oxidative phosphorylation requires 4 H+ moved from the P side of the membrane to the N side. 3 H+ move through ATP synthase, and the 4th H+ is required for co-transport with
(A) ATP; (B) phosphate; (C) CoA-SH; (D) pyruvate.

              19. When epinephrine binds a muscle cell receptor,                   is more active, and glycogen synthesis                       .
(A) glycogen synthase, increases; (B) PKA, decreases;
(C) PP1, decreases; (D) PKA, increases.

              20. When insulin binds a liver cell receptor,                                 is more active, and glycolysis               .
(A) PKA, increases; (B) PP1, increases; (C) PKA, decreases; (D) PP1, decreases.

              21. This molecule is an intermediate in the reaction catalyzed by               , which is a/n                               .
(A) aconitase, hydrolase; (B) aconitase, isomerase;
(C) phosphoglucose mutase, transferase;
(D) succinyl-CoA synthetase, ligase.

              22. For a cell that uses glycerol-3-phosphate dehydrogenase in the presence of O2, the net energy yield in ATP from completely degrading one glucose residue removed from glycogen is (A) 30 ATP; (B) 31 ATP; (C) 32 ATP; (D) 37 ATP.

              23. Carboxin is an inhibitor of complex II. Treatment with carboxin would increase       concentration and                          O2 consumption
(A) QH2, reduce; (B) succinyl-CoA, not change; (C) fumarate, increase;
(D) succinyl-CoA, reduce.
Assume you are studying mitochondria that are well supplied with citrate, and the citric acid cycle is functioning normally until you add the treatment.

              24. Adenine nucleotide translocase moves ADP3− and ATP4− across the inner membrane. Moving        is unfavorable, but moving                       is favorable. (A) ADP only, ADP and ATP; (B) ATP only, ADP and ATP;
(C) ADP and ATP, ADP only; (D) ADP and ATP, ATP only.

              25. The mass action ratio is the [products]/[reactants] ratio in the equation:
ΔG = ΔG°′ + R T ln ([products]/[reactants]). Which choice is an inhibitor of citrate synthase because it increases the mass action ratio of a citric acid cycle product?
(A) ATP; (B) AcCoA; (C) AMP; (D) NADH.

              26. The malate shuttle requires two enzymes. In the presence of O2, the cytosol enzyme converts (A) malate to oxaloacetate; (B) oxaloacetate to malate;
(C) malate to glycerol-3-phosphate; (D) malate to dihydroxyacetone-phosphate.

27. In skeletal muscle, glycogen phosphorylase is regulated both covalently and allosterically.
a. Write the reaction catalyzed by glycogen phosphorylase. (3)
b. Covalent modification of glycogen phosphorylase requires two different reactions.
       Write one of the reactions. Name the enzyme that catalyzes the reaction and the
       conformation (R or T) that is stabilized as a result of the reaction. (4)
c. What is the effect on glycogen phosphorylase b activity of increasing [AMP]? (1)

28. The following half reactions and reduction potentials are all involved in some part of electron transport. Choose the appropriate half reactions. F = 96,480 J/V-mole; T = 298 K.
a. Write the complete oxidation-reduction reaction catalyzed by Complex II.
b. Calculate ΔE°′ for the reaction.
c. Calculate ΔG°′ for the reaction.
d. Since ΔG°′ for ATP hydrolysis = − 30.5 kJ/mole, how many ATP's can be synthesized,
     theoretically, as a result of the oxidation-reduction reaction catalyzed by Complex II?

Reduction half-reaction

E°′ (V)

1/2 O2 + 2 H+ + 2 e− → H2O

0.816

cytochrome c (Fe3+) + e− → cytochrome c (Fe2+)

0.254

Q + 2 H+ + 2 e− → QH2

0.045

fumarate + 2 H+ + 2 e− → succinate

0.031

NAD+ + 2 H+ + 2 e− → NADH + H+

− 0.320

29. The enzymes citrate synthase, aconitase, and isocitrate dehydrogenase catalyze the first
      three reactions in the citric acid cycle. (10)
a. Draw the molecules in the three reactions in order, starting with the substrate(s) for
      citrate synthase.
b. Choose two of the three enzymes and name the type of reaction each catalyzes.
     (oxidative decarboxylation, oxidation-reduction, substrate phosphorylation, etc.)

30. Pyruvate dehydrogenase (PDH) is a large enzyme complex in the mitochondrial matrix.
a. Write the overall reaction catalyzed by PDH. (4)
b. The diagram below shows an intermediate in the reaction. Which enzyme (E1, E2, or E3)
      is involved, and what coenzyme has a bond to the intermediate? (2)
c. What happens next in the reaction? (2)

      a.                                                                                                                                                  

b.

enzyme:

coenzyme:

      c.

31. Each of the following questions is about regulation of carbohydrate metabolism.
Answer one (your choice). (6)
a. Write the reactions catalyzed by PFK-2 and FBPase-2.
            Explain why the reactions are coupled together.
b. Describe the effects of insulin and glucagon on the pathways of glycolysis and
             gluconeogenesis in a liver cell. Be specific about the enzymes affected.
c. The carriers GLUT2, T1, and T2 are found only in liver cells. What unique function
             does a liver cell have, and how are these proteins involved?

 

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