47. Which of the following statements about the reactions involved in the synthesis of deoxyribonucleotides is false?
(A) Deoxyribonucleotides are derived from the corresponding ribonucleotides by direct reduction at the 2'-carbon atom of the D-ribose to form the 2'-deoxy derivative.
(B) Formation of deoxyribonucleotides is catalyzed by ribonucleotide reductase, in which its substrates are ribonucleoside diphosphates.
(C) Ribonucleotide reductase is notable in that its reaction involves free radicals in biochemical transformations.
(D) Nucleoside diphosphate kinase catalyzes the reaction: dTDP + ATP → dTTP + ADP.
(E) The immediate precursor of thymidylate (dTMP) is dUMP. The conversion of dUMP to dTMP is a reaction of deamination.

43. E'° of the NAD+/NADH half reaction is -0.32 V. The E'° of the oxaloacetate/malate half reaction is -0.175 V. When the concentrations of NAD+, NADH, oxaloacetate, and malate are all 10⁻5 M, the "spontaneous" reaction is: (A) malate + NAD⁺ → oxaloacetate + NADH + H⁺. (B) malate + NADH + H⁺ → oxaloacetate + NAD⁺. (C) NAD⁺ + NADH + H⁺ → malate + oxaloacetate. (D) NAD⁺ + oxaloacetate → NADH + H⁺ + malate. (E) oxaloacetate + NADH + H⁺ → malate + NAD⁺.

44. Fructose in the diet or fructose from sucrose in the diet can be a source of calories for fat synthesis in the liver because: (A) ketoses are fattening. (B) fructose enters glycolysis after the primary regulation point, PFK-1. (C) fructose provides a net of four ATP from glycolysis. (D) fructose enters the branch of glycolysis that forms fat. (E) glycerol (the "backbone" of triacylglycerols) comes specifically from fructose.

45. Many of the enzymes of the Calvin cycle are also involved in __________; however, the glyceraldehyde-3-phosphate dehydrogenase of the Calvin cycle is specific for__________. (A) glycolysis; NADPH (B) citric acid cycle; NADH (D) citric acid cycle; NADPH (E) None of the above. (C) glycolysis; FADH₂

46. A mutase catalyzes which of the reactions, and belongs to which class of enzymes? (A) 2-phosphoglyceratephosphoenolpyruvate + H₂O; lyase (B) pyruvate + NADH + H⁺ lactate + NAD⁺; oxidoreductase (C) 3-phosphoglycerate 2-phosphoglycerate; isomerase (D) dihydroxyacetone phosphateglyceraldehyde-3-phosphate; isomerase (E) glucose-6-phosphatefructose-6-phosphate; isomerase

48. 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. (D) Only 4 is correct. (B) 3 and 4 are correct. (E) Only 5 is correct. (C) Only 2 is correct.

49. All of the following are a coenzyme or a precursor of a coenzyme except: (A) thiamin. (B) riboflavin. (C) retinol. (D) niacin. (E) biotin.

50. Glucose labeled with 14C in C-3 and C-4 is completely converted to acetyl-CoA via glycolysis and the pyruvate dehydrogenase complex. What percentage of the acetyl-CoA molecules formed will be labeled with 14C, and in which position of the acetyl moiety will the 14C label be found? (A) 100% of the acetyl-CoA will be labeled at C-1 (carboxyl). (B) 100% of the acetyl-CoA will be labeled at C-2. (C) 50% of the acetyl-CoA will be labeled, all at C-2 (methyl). (D) No label will be found in the acetyl-CoA molecules. (E) Not enough information is given to answer this question.

1. No one can say what causes the oceans' chemistry to change so dramatically from time to time, but the opening and shutting of ocean ridges would be an obvious possible ________. (A) charlatan (B) confidant (C) countenance (D) culprit (E) cynic

2. Claudia Townsend, associate professor of marketing in the Miami Herbert Business School, weighed in on the blockbuster roll out of the Barbie and Oppenheimer movies that ________ massive success at the box office. (A) scored (B) stigmatized (C) stipulated (D) stunted (E) succumbed

3. The ________ VUCA has been used to refer to the volatile, uncertain, complex, and ambiguous nature of the times we live in. (A) vocalic (B) antonym (C) acronym (D) etymon (E) alias