37. The NADH produced by glycolysis produces different amounts of ATP in different tissues. This is because:
(A) some tissues can utilize cytosolic NADH to produce ATP； however, some tissues cannot.
(B) different tissues have different energy need.
(C) different tissues have different shuttle system to transport cytosolic NADH into mitochondria.
(D) the efficiency of the respiratory chain in different tissues are different.
(E) the averaged amounts of mitochondria in the cells of different tissues are different.

33. During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to if glycolysis is to continue. Which of the following is the most important reaction involved in the reoxidation of NADH? (A) glucose 6-phosphate → fructose 6-phosphate (B) dihydroxyacetone phosphate → glycerol 3-phosphate (C) pyruvate → lactate (D) isocitrate → α-ketoglutarate (E) oxaloacetate → malate

34. In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change (AG) be negative, enabling the reaction to proceed to the right? (A) Under standard conditions, enough energy is released to drive the reaction to the right. (B) If the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate. (C) The reaction will not go to the right spontaneously under any conditions because the is positive. (D) When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products. (E) None of the above.

35. In normal mitochondria which statement regarding the rate of NADH consumption is   correct  ? 　 1. Be increased in active muscle, decreased in inactive muscle. 　 2. Be very low if the ATP synthase is inhibited, but increase when an uncoupler is added. 　 3. Decrease if mitochondrial ADP is depleted. 　 4. Decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3 complex. (A) 1, 2, and 3 are correct. (B) 1, 3, and 4 are correct. (C) 2, 3, and 4 are correct. (D) 1, 2, and 4 are correct. (E) All are correct.

36. Which of the following is   correct   concerning the mitochondrial ATP synthase? (A) When it catalyzes the ATP synthesis reaction, the AG is actually close to zero. (B) It consists of F, and F₁ subunits, both of which are transmembrane (integral) polypeptides. (C) It can synthesize ATP after it is extracted from broken mitochondria. (D) It is actually an ATPase and only catalyzes the hydrolysis of ATP. (E) It catalyzes the formation of ATP even though the reaction has a large positive ∆Gº.

38. P/O ratio in electron transport and oxidative phosphorylation is defined as: (A) molecules of phosphate released from ATP per oxygen utilized by muscle tissue. (B) molecules of ATP formed per two electrons flowing through electron transport chain. (C) P； uptake per oxygen atom by mitochondria. (D) ratio of atoms of phosphorous to oxygen in phosphate (Pi). (E) None of the above.

39. Which of the following statements about mitochondrial transport systems is(are)   correct  ? 1. Glycerophosphate shuttle converts cytosolic FADH2 to mitochondrial NADH. 　　 2. Glycerophosphate shuttle transports "NADH electron equivalents" across the mitochondrial membrane to yield 1.5 ATP/NADH. 　 3. Malate-aspartate shuttle converts cytosolic NADH to mitochondrial FADH2. 　 4. One form of glycerol-3-phosphate dehydrogenase in the glycerophosphate shuttle is a flavoprotein. 　 5. ATP-ADP translocase transfers ATP and a proton from matrix to cytosol while transferring ADP from cytosol to matrix. (A) 2 and 4 are correct. (B) 1, 3, and 5 are correct. (C) Only 5 is correct. (D) 4 and 5 are correct. (E) Only 4 is correct.

40. The oxidation of a particular hydroxy substrate to a keto product by mitochondria has a P/O ratio of less than 2. The initial oxidation step is very likely directly coupled to the: (A) reduction of a pyridine nucleotide. (B) oxidation of a flavoprotein. (C) reduction of cytochrome a3. (D) oxidation of a pyridine nucleotide. (E) reduction of a flavoprotein.

41. 2,4-Dinitrophenol and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4-Dinitrophenol is an uncoupling agent； oligomycin blocks the ATP synthesis reaction itself. Therefore,2,4-dinitrophenol will: (A) diminish O2 consumption in the presence of oligomycin. (B) block electron transfer in the presence of oligomycin. (C) allow oxidative phosphorylation in the presence of oligomycin. (D) allow electron transfer in the presence of oligomycin. (E) None of the above.

42. Consider a liver cell carrying out the oxidation of glucose under aerobic conditions. Suppose that we added a very potent and specific inhibitor of the mitochondrial ATP synthase, completely inhibiting this enzyme. Which of the following descriptions is(are)   correct  ? 1. The rate of oxygen consumption will increase.  2. ATP production in the cell will quickly drop to zero. 3. The citric acid cycle will speed up to compensate. 4. Mitochondrial ATP synthesis will cease, but to compensate, cells will accelerate the production of ATP by glycolysis, preventing ATP levels from dropping to zero. 5. The cell will switch to fatty acid oxidation as an alternative to glucose oxidation. (A) 1 and 5 are correct. (B) 3 and 4 are correct. (C) Only 2 is correct. (D) Only 4 is correct. (E) Only 5 is correct.

43. A diagram of ATP synthase is shown. If an ATP synthase contains 12 c subunits, 3 a subunits and3 ẞ subunits, how many protons must pass through this complex for every ATP molecule synthesized and transported to the cytosol, assuming that each ATP synthesized requires one proton for transport to the cytosol? (A) 3 (B) 4 (C) 5 (D) 12 (E) 13