複選題
38. The urea cycle and citric acid cycle are linked by
(A) arginine and fumarate.
(B) citrulline and ornithine.
(C) fumarate and aspartate.
(D) ornithine and arginine.
(E) citrulline and argininosuccinate.

34. Which of the following statements about the following reaction is correct?Citrate + COA-SH + ATP → Acetyl-CoA + Oxaloacetate + ADP + Pi(1) The reaction is catalyzed by ATP citrate lyase.(2) Formation of acetyl-CoA in this reaction provides the starting materials for lipid metabolism.(3) Formation of oxaloacetate in this reaction provides an indirect means for the production of the NADPH for lipid metabolism. (A) 1 and 2 are correct. (B) 1 and 3 are correct. (C) 2 and 3 are correct. (D) All of above are correct. (E) None of above is correct.

35. Concerning the pathway for ketone body synthesis, all of the following make sense except (A) Three acetyl-CoA molecules can become HMG-CoA. (B) HMG-CoA is used for cholesterol and ketone body synthesis. (C) HMG-CoA lyase produces acetoacetate and acetyl-CoA. (D) Acetoacetate is oxidized to beta-bydroxybutyrate and acetone. (E) The rate of ketone body production is proportional to the excess acety! CoA in the mitochondria.

36. Which of the following statement(s) is correct regarding the regulation of fatty acid synthesis and breakdown?(1) Malonyl-CoA is the key repressor for fatty acid degradation due to the inhibition of fatty acid entry into mitochondria.(2) Insulin signaling triggers the dephosphory lation of acetyl-CoA carboxylase to synthesize malonyl-CoA. (3) The reaction catalyzed by fatty acid synthase is the rate-limiting step in the biosynthesis of fatty acids. (B) 2 and 3 (C) 1 and 3 (E) All of above are correct. (A) 1 and 2 (D)2 only

37. The synthesis of 1 molecule of cholesterol requires________ molecule of isopentenyl pyrophosphate , with each molecules of isopenteny1 pyrophosphate requiring________ molecules of acetyl-CoA. (A) 4；3 (B) 5；2 (C) 6；3 (D) 6；2(E) 7；3

39. Approximately how many ATP molecules are netted from the complete oxidation of stearic acid (C-18)? (A)2 (B)4 (C) 32 (D) 88 (E) 120

40. Gout is caused by high levels of uric acid. What are the possible causes? (A) Glucose-6-phosphatase deficiency (B) Phosphoribosylpyrophosphate (PRPP) synthetase mutation (C) Hypoxanthine-guanine phosophoribosyltransferase (HGPRT) deficiency (D) All of these are possible causes. (E) None of the above.

複選題41. What situation is most likely to cause the formation of ketone bodies?(1) Starvation (2) Gout (3) High in lipid diet (4) Regular meal(5) High in carbohydrate diets (6) Diabetes(7) Exercising (8) Intake of short-chain fatty acids (B) 3, 4, and 7 (C) 5, 6, and 7 (D) 2, 4, and 8 (A) 1,2, and 3 (E) 1, 6, and 8

42. Glucose breakdown in certain mammalian and bacterial cells can occur by mechanisms other than classic glycolysis. In most of these, glucose 6-phosphate is oxidized to 6-phosphogluconate, which is then further metabolized by: (A) an aldolase-type split to form glyceric acid and glyceraldehyde 3-phosphate. (B) an aldolase-type split to form glycolic acid and erythrose 4-phosphate. (C) conversion to 1,6-bisphosphogluconate. (D) decarboxylation to produce keto- and aldopentoses. (E) oxidation to a six-carbon dicarboxylic acid.

43._____is often used in carboxylation reactions while ______is often used in decarboxylation reactions. (A)thiamine pyrophosphate； lipoate (B) lipoate； biotin (C) biotin； thiamine pyrophosphate (D) pyridoxal-5-phosphate；biotin (E) lipoate； pyridoxal-5-phosphate

44. In the citric acid cycle, citrate is isomerized to isocitrate by aconitase. H2O was first abstracted  from citrate, and then rehydrated with H– and HO–adding back in opposite positions to produce  isocitrate. This reaction catalyzed by aconitase is quite stereospecific. As citrate has a total of four chemically equivalent hydrogens (labeled as H1~H4 in the figure), only one of the four HsㅡC-HA hydrogens, the pro-R H atom of the pro-R arm of citrate, is abstracted during the reaction of the H2O abstraction by aconitase.  Which one of the hydrogens in the citrate molecule shown in the figure is the pro-R H atom of the pro-R arm?(A) H1 (B) H2 (C) H3 (D) H4 (E) None of them.