44. Oxaloacetate uniformly labeled with¹⁴C (ie., with equal amounts of¹⁴C in cach 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?
(A) All
(B) 1/2
(C) 1/3
(D) 1/4
(E) 3/4

40. The 6-phosphogluconate dehy drogenase reaction in the pentose phosphate pathway is an example of________ and results in the production of_________. (A) substrate-level phosphorylation; ATP (B) oxidative-decarboxylation; NADPH (C) TPP-assisted decarboxylation; NADH (D) phosphate addition; ADP (E) None of the above.

41. When a cell with the pentose phosphate pathway has need for more pentose phosphates, but not for additional NADPH: (A) glucose-6-phosphate dehydrogenase is activated. (B) the oxidative and non-oxidative enzymes of the pentose phosphate pathway are active. (C) the non-oxidative enzymes produce pentose phosphates from fructose-6-phosphate and glyceraldehyde-3-phosphate. (D) all enzymes of glycolysis and pentose phosphate pathway are active. (E) None are true.

42.In the Southern hybridization procedure, the gel after electrophoresis is treated with NaOH and before blotting. What is the primary function of the alkaline treatment? (A) It neutralizes any acid soluble impurities in the gel. (B) It cleaves the DNA into smaller fragments to permit greater efficiency of transfer. (C) It inactivates any restriction endonucleases that may be in the gel.. (D) It neutralizes any acidic phosphate groups that might prevent hybridization. (E) It denatures the duplex DNA to single-stranded DNA (ssDNA).

43. A characteristic of the glycerophosphate shuttle is: (A) It shuttles NADH across the mitochondrial membrane to yield 2.5 ATP/ADH. (B) It shuttles "NADH electron equivalents" across the mitochondrial membrane to yield 1.5 ATPNADH. (C) It only operates efficiently when the [NADH] in the cytoplasm is higher than in the matrix. (D) Malate is a key component in the shuttle process. (E) Aspartate is a key component in the shuttle process.

45. 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) oxidation of a flavoprotein. (B) oxidation of a pyridine nucleotide. (C) reduction of a flavoprotein. (D) reduction of a pyridine nucleotide. (E) reduction of cytochrome as.

46. Which of the following statements concerning the biosynthesis of fatty acids is false? (A) Fatty acid synthesis occurs in the cytosol of many organisms but in the chloroplasts of plants. (B) Biosynthesis of fatty acids requires the participation of a three-catbon intermediate, malony1-Co A, which is formed via the reaction catalyzed by acetyl-CoA carboxylase. (C) In nonphotosynthetic eukaryotes, nearly all the acetyl-CoA used in fatty acid synthesis is formed in mitochondria, and the acetyl group used in fatty acid synthesis is shuttled out of mitochondria as citrate. (D) If malonyl-CoA is synthesized from 14CO2 and unlabeled acetyl-CoA, and the labeled product is then used for fatty acid synthesis, the final product (fatty acid) will have radioactive carbon in every even-numbered C-atom. (E) Fatty acid biosynthesis uses NADPH exclusively, whereas oxidation uses NAD+ exclusively.

47. What of the following is the essential ingredient for the biosynthesis of fatty acid? (A) (B) (C) (D) (E)

48. Given the saturated fatty acid,, how many could ATPs be produced by the B-oxidation of the fatty acid? (A) 68 (B) 62 (C) 64 (D) 48 (E) 50

49. Of the following biochemical compounds, what are ketone bodies? (A)①④(B)②⑤ (C)①③ (D)②④ (E)④⑤

50. Shown is the biological synthesis of cysteine from serine in bacteria. What is the chemical structure of compound A?(A) (B) (C) (D)(E)