43. Glutamine synthetase plays an important role in the incorporation of ammonia (or ammonium ions) into glutamine. Which of the following mechanisms of covalent modification controls the activity of glutamine synthetase?
(A) Phosphorylation/dephosphorylation.
(B) Adenylation/deadenylation.
(C) Acetylation/deacetylation.
(D) Methylation/demethylation.
(E) None of the above.

39. Which of the following is   not   true about cyclic electron flow of photophosphorylation? (A) Cyclic electron flow produces more NADPH per photon than noncyclic electron flow. (B) Cyclic electron flow involves only photosystem I. (C) Plastocyanin is required for cyclic electron flow. (D) Cyclic electron flow leads to the build-up of a proton gradient. (E) Cyclic electron flow does not produce O2.

40. Which of the following statements about mitochondrial transport systems is correct? (A) Malate-aspartate shuttle: converts cytosolic NADH to mitochondrial FADH2. (B) ATP-ADP translocase: transfers ATP and a proton from matrix to cytosol while transferring ADP from cytosol to matrix. (C) Glycerophosphate shuttle: converts cytosolic FADH2 to mitochondrial NADH. (D) The malate-aspartate shuttle is irreversible while the glycerophosphate shuttle is reversible. (E) None of the above are correct.

複選題41. 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 ATP/NADH. (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.

42. Which of the following correctly and completely describes electron movement in electron transport? (A) NADH → complex I → complex III → coenzyme Q→ Complex IV → O2 (B) [FADH2] → complex II → cytochrome c → complex III → coenzyme Q → Complex IV → O2 (C) NADH → complex I → coenzyme Q→ complex III -~-→ cytochrome c → Complex IV → O2 (D) [FADH2] → complex I → coenzyme Q→ complex III → Complex IV → O2 (E) None of the above

44. Most cancers depend on a high rate of aerobic glycolysis for their continued growth and survival. Paradoxically, some cancer cell lines also display addiction to glutamine. Which of the following is   not   true for the possible mechanism behind this glutamine addiction: (A) Glutamine is an essential amino acid. (B) Glutamine provides nitrogen for nucleotide synthesis. (C) Glutamine provides substrate for mitochondrial citric acid cycle. (D) Glutamine provides nitrogen for protein synthesis. (E) Glutamine activates mTORC1 signaling.

45. Insulin resistance causes an increase in gluconeogenic activity in the liver due to the lack of glucose. What serves as the primary carbon source for gluconeogenesis under these conditions? (A) Amino acids. (B) Glycerol. (C) Fructose. (D) Acetyl-CoA. (E) Ketone bodies

46. Considered the following transamination reaction in amino acid biosynthesis, what amino acid would be produced? (A) Glu. (B) Asp. (C) Gln. (D) Asn. (E) Arg.

47. Given the saturated fatty acid shown below, how many ATPs can be produced when it is completely metabolized by β-oxidation? Some useful info:  i. In the TCA cycle, one Acetyl-CoA gives 3 NADHs, 1 FADH2, and 1 GTP. ii. One NADH produces 2.5 ATPs. iii. One FADH2 produces 1.5 ATPs. (A) 50. (B) 52. (C) 60. (D) 62. (E) 64.

48. One of the hopes for use of recent knowledge gained about non-coding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs? (A) Exploring a way to turn on the expression of pseudogenes. (B) Targeting siRNAs to disable the expression of an allele associated with autosomal recessive disease. (C) Targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease. (D) Creating knock-out organisms that can be useful for pharmaceutical drug design. (E) Looking for a way to prevent viral DNA from causing infection in humans.

49. The role of a metabolite that controls a repressible operon is to (A) bind to the promoter region and decrease the affinity of RNA polymerase for the promoter. (B) bind to the operator region and block the attachment of RNA polymerase to the promoter. (C) increase the production of inactive repressor proteins. (D) bind to the repressor protein and inactivate it. (E) bind to the repressor protein and activate it.