41. Which one is incorrect regarding the intermediates and precursors in lipid metabolism?
(A) Cis-Δ² enoyl CoA in β oxidation.
(B) Mevalonate in cholesterol synthesis.
(C) Phosphatidic acid in glycerolphospholipid synthesis.
(D) Serine and palmitoyl-CoA in sphingolipid synthesis.
(E) Δ³-Isopentenyl pyrophosphate is the precursor of vitamin A, E, K.

37. Which one of the following enzymatic activities would be decreased by thiamine deficiency? (A) Fumarase. (B) Isocitrate dehydrogenase. (C) Malate dehydrogenase. (D) Succinate dehydrogenase. (E) α-Ketoglutarate dehydrogenase complex.

38. The conversion of 1 mole of fructose 1,6-bisphosphate to 2 mole of pyruvate by the glycolytic pathway results in a net formation of: (A) 1 mole of NADH and 1 mole of ATP. (B) 2 mole of NAD⁺ and 4 mole of ATP. (C) 1 mole of NAD⁺ and 2 mole of ATP. (D) 2 mole of NADH and 4 mole of ATP. (E) 2 mole of NADH and 2 mole of ATP.

39. Which one of the following statements is true? 1. In glycolysis, ATP is synthesized by both substrate-level and oxidative phosphorylation. 2. Fructose-1,6-bisphosphate is an allosteric factor for controlling by phosphofructokinase. 3. In the glyceraldehyde-3-phosphate dehydrogenase reaction, the amino acid cysteine is important in adding a second phosphate to glyceraldehyde phosphate. 4. During anaerobic metabolism in red blood cells, the carbons of glucose end up in lactic acid. 5. Phosphofructokinase and pyruvate kinase both are tetrameric. (A) All are true. (B) 1 and 4 are not true. (C) 5 is not true. (D) 1, 3 and 5 are not true. (E) 2 and 4 are not true.

40. Which one is incorrect regarding the rate limiting steps of lipid metabolism? (A) Carnitine acyltransferase I in β oxidation. (B) Acetyl-CoA carboxylase in fatty acid synthesis. (C) HMG reductase in phosphatidylcholine synthesis. (D) Phosphatidic acid phosphatase in phospholipid synthesis. (E) Serine palmitoyltransferase in sphingolipid synthesis.

42. Which molecule contains an phosphoanhydride bond? (A) DNA. (B) RNA. (C) UMP. (D) ADP. (E) cAMP.

43. In the TCA cycle, carbon enters the cycle as ____ and exits as with metabolic energy captured as ____. (A) malonyl-CoA； water； NADH； [FADH2]； ATP (B) acetyl-CoA； CO2； ATP； NADH； [FADH2] (C) succinyl-CoA； CO2； ATP； NADH； NADPH (D) malonate； water； NADH； ATP； NADPH (E) acetyl-CoA； CO2； NADH； ATP； NADPH

44. Uncoupling of mitochondrial oxidative phosphorylation: (A) slows the conversion of glucose to pyruvate by glycolysis. (B) allows continued mitochondrial ATP formation but halts O2 consumption. (C) halts all mitochondrial metabolism. (D) slows down the citric acid cycle. (E) halts mitochondrial ATP formation but allows continued O2 consumption.

45. Glutamine synthetase plays an important role in the incorporation of ammonia into glutamine. Which of the following post-translational modification controls the activity of glutamine synthetase? (A) Phosphorylation/dephosphorylation. (B) Adenylation/deadenylation. (C) Acetylation/deacetylation. (D) Methylation/demethylation. (E) None of the above.

46. Chorismate is an important precursor in the synthesis of all of the following   except  : (A) vitamin K. (B) folic acid. (C) arginine. (D) tyrosine. (E) tryptophan.

47. Which of the following statement about homocysteine is   not   true: (A) It is a homologue of cysteine, differing by addition of methylene bridge (-CH2-). (B) It is found in some proteins. (C) It is biosynthesized from methionine by the removal of its terminal Ce methyl group. (D) It can be recycled into methionine or converted into cysteine with the aid of certain B-vitamins. (E) It is a possible risk factor for coronary artery disease.