68. The brain produces most of its energy by the oxidation of glucose； during long-term fasting. however, it can cover more than half of its energy needs from__________.
(A) anaerobic glycolysis
(B) oxidation of its stored glycogen
(C) oxidation of free fatty acids
(D) oxidation of amino acids
(E) oxidation of ketone bodies

64. Which of the following statements regarding circulating immunoglobulins is correct?(1) They are produced by B-cell-derived plasma cells.(2) Their diversity is generated by gene rearrangements in the developing B cells.(3) Each immunoglobulin producing cell generates only one kind of immunoglobulins. (A)(1) and (2) (B) (1) and (3) (C) (2) and (3) (D) None of the above is correct (E) All of the above are correct

65. During long-term fasting, the liver produces acety!-CoA by the B-oxidation of fatty acids. What is the major metabolic fate of this acetyl-CoA? (A) Fatty acid biosynthesis (B) Gluconeogenesis (C) Amino acid biosynthesis (D) Ketogenesis (E) Oxidation in the TCA cycle

66. On a high-carbohydrate, low-fat diet, carbohydrates are converted into fat through a series of reactions listed below. What is the correct sequence of these reactions?(1) esterification(2) glycolysis(3) fatty acid biosynthesis (A)(1),(2),(3) (B)(1),(3),(2) (C)(2),(3),(1) (D)(2),(1),(3) (E)(3), (2),(1)

67. The molecule shown here is acetylsalicylic acid (aspirin). What kind of electrical charge does aspirin carry in the stomach at a pH value of 2 and in the small intestine at a ph value of 7?  (A) Negatively charged in the stomach； positively charged in the intestine (B) Negatively charged both in the stomach and the intestine (C) Uncharged in the stomach: negatively charged in the intestine (D) Uncharged both in the stomach and the intestine (E) Uncharged in the stomach； positively charged in the intestine

69. Which of the following reactions is not the reversible reaction in glycolysis? (A) Glucose 6-phosphate to fructose 6-phosphate (B) Fructose 6-phosphate to fructose 1,6-bisphosphate (C) Glyceraldehyde 3-phosphate to 1.3-bisphosphoglycerate (D) 3-Phosphoglycerate to 2-phosphoglycerate (E) 2-Phosphoglycerate to phosphoenolpyruvate

70. Which amino acid is the common donor for methyl transfer? (A) Met (B) Ala (C)Gly (D) Ser (E) Lys

71. Which of the following best describes the metabolic outcome of glycolysis for the degradation of glucose? (A) 2 Pyruvate. 4 ATP, 4 NADH (B) 2 Pyruvate, 2 ATP, 2 NADH (C) 2 Pyruvate, 4 ATP, 2 NADH (D) 4 Pyruvate, 2 ATP, 4 NADH (E) 4 Pyruvate, 4 ATP, 2 NADH

72. Which step of the TCA cycle can generate GTP directly? (A) Citrate to isocitrate (B) Isocitrate to a-ketoglutarate (C) a-Ketoglutarate to succinyl-CoA (D) Succinyl-CoA to succinate (E) Succinate to fumarate

73. Fatty acids with 14 or high carbons require_________for transport into mitochondria. (A) glycerol-3-phosphate shuttle (B) carnitine shuttle (C) clathrin (D) citrate shuttle (E) malate-aspartate shuttle

74. The mutation that oceurs in sickle cell anemia belongs to_________. (A) silent mutation (B) missense mutation (C) nonsense mutation (D) frameshift mutation (E) insertion mutation