80. Which of the following statements about citric acid cycle are correct? ① Pyruvate dehydrogenase links glycolysis to the citric acid cycle. ② The products of citric acid cycle are not used for the production of ATP in cells. ③ The product of glycolysis forms acetyl-CoA for entering citric acid cycle. ④ Its intermediates are not used by other metabolic reactions. ⑤ The citric acid cycle is also called as the Krebs cycle or the tricarboxylic cycle.
(A) ①②③
(B) ①②④
(C) ①②⑤
(D) ①③④
(E) ①③⑤

76. DNA polymerase I synthesizes new DNA with very high fidelity, due to its __________. (A) high processivity (B) 3’→5’ exonuclease activity (C) helicase association with the primase (D) 5’→3’ exonuclease activity (E) all of the above

77. Which of the following statements about urea cycle are correct? ① Urea is the end product of the urea cycle. ② Inherited defects in urea cycle cause hyperammonemia. ③ The synthesis of fumarate by the urea cycle can be used as a precursor for glucose synthesis. ④ The urea cycle begins with the formation of ornithine in mitochondria. ⑤ ATP is not consumed in urea cycle. (A) ②③④ (B) ②③⑤ (C) ①②③ (D) ①④⑤ (E) ③④⑤

78. Which of the following statements is correct regarding the blood glucose level of non-insulin dependent diabetics tend to compare to that of normal individuals? (A) Blood glucose levels of diabetics tend to be very stable, but at a higher level. (B) Blood glucose levels of diabetics tend to be variable and higher. (C) Blood glucose levels decrease more rapidly following a meal, often dropping lower than is tolerable. (D) Blood glucose levels average the same level in diabetics, but reach higher peaks for short periods. (E) None of the above.

79. One turn of the citric acid cycle generates __________. (A) 2 FADH2, 3 ATP, 1 NADH (B) 1 NAD+ , 2 FADH2, 1 ATP (C) 1 GTP, 3 NADH, 1 FADH2 (D) 1 FAD, 2 ATP, 3 NADH (E) 1 FADH2, 1 GTP, 2 NADH

81. β-oxidation of fatty acids, which one of the following reactions is correct? (A) Two NADH are produced for each acetyl-CoA. (B) Oxidation of an 18-carbon fatty acid produces six molecules of propionyl-CoA. (C) Uses only even–chain, saturated fatty acids as substrates. (D) Uses NADP+ . (E) Occurs by a repeated sequence of four reactions. 

82. Which of the following is correct regarding the reaction shown below? pyruvate + HCO3 − + ATP → oxaloacetate + ADP + Pi ① It requires the direct transport of oxaloacetate across the membrane. ② It utilizes the malate-aspartate shuttle in some species. ③ It is essential for gluconeogenesis. ④ Its reactants require the function of enzymes which are only found in the cytosol. (A) ①② (B) ②③ (C) ③④ (D) ①③ (E) ②④

83. In the process of glycolysis, several reactions take place. Which of the following statements related to them are correct? ① Two molecules of pyruvate are produced by glycolysis. ② Under anaerobic condition, pyruvate can be oxidized to CO2, generating more ATP molecules. ③ Hexokinase is involved in glycolysis. ④ Frucose-1,6-biphosphate is not generated from glucose-1,6-biphosphate. ⑤ 1,3-Bisphosphoglycerate is generated from glycolysis. ⑥ Eight ATP molecules are generated from the conversion of glucose to pyruvate. (A) ②④⑤⑥ (B) ①②③④ (C) ②③④⑥ (D) ①③④⑤ (E) ①②④⑥

84. Which of the following descriptions regarding genetic code is NOT correct? (A) The genetic code is degenerate, and many codes can specify a certain amino acid. (B) The first two positions of a codon are more important, and mutation in the third position often does not change the sense of the codon. (C) One codon consists of three bases. (D) Missense mutation changes only one codon and sometimes does not cause phenotypic change. (E) Frameshift mutations can be suppressed by a suppressor tRNA molecule.

85. What moiety can NOT be found in a sphingomyelin? (A) Sphingosine (B) Acetylcholine (C) Ceramide (D) Fatty acid (E) Phosphoric acid

86. Which of the following compounds is NOT derivative of cholesterol? (A) Bile acids (B) Estrogens (C) Androgens (D) Glucocorticoids (E) Prostaglandins