15. A cell that is unable to synthesize or obtain tetrahydrofolic acid (H₄ folate) would probably be deficient in the biosynthesis of:
(A) dCMP.
(B) GMP.
(C) orotate.
(D) dTMP.
(E) UMP.

11. The most sensitive indicator of the energetic status of the cell is the concentration of: (A) AMP. (B) ADP. (C) ATP. (D) cAMP. (E)glucose.

12. In a biotin-dependent carboxylation, _______provides the energy for activation of_________ (A) acetyl CoA； carbon dioxide (B) ATP； lysine amine group (C) NADH； bicarbonate (D) ATP； bicarbonate (E) acetyl CoA； carboxyl group

13. Which of the following compounds has the largest negative value for the standard free-energy change (AG") upon hydrolysis? (A) Acetic anhydride (B) Glucose 6-Phosphate (C) Glutamine (D) Glycerol 3-phosphate (E) Lactose

14. Under anaerobic conditions, skeletal muscle generates lactate from pyruvate to: (A) lower the pH. (B) promote release of oxygen from hemoglobin. (C) generate additional ATP. (D) be warning of muscle fatigue. (E) regenerate NAD+ for further glycolysis.

16. In triacylglyceros, the glycerol and the fatty acid moieties is joined covalently in a: (A) phosphodieaster bond. (B) ester bond. (D) amide bond. (E) N-β-glycosyl bond. (C) ether bond.

17. 2,4-Dinitrophenol and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4-Dinitrophenol is an uncoupling agent； oligomycin blocks the ATP synthesis reaction itself. Therefore, 2,4-dinitrophenol will: (A) allow electron transfer in the presence of oligomycin. (B) allow oxidative phosphorylation in the presence of oligomycin. (C) block electron transfer in the presence of oligomycin. (D) diminish O2 consumption in the presence of oligomycin. (E) None of the above

18. A molecule such as 2,4-dinitrophenol (2,4-DNP) works to uncouple the proton gradient. Which of the following is true about 2,4-DNP? (A) 2,4-DNP is protonated in the matrix and deprotonated in the intermembrane space. (B) The presence of an uncoupler results in an increase in the activity of the TCA cycle and electron transport. (C) 2,4-DNP is a very ineffective uncoupler because its hydrophobic structure prevents it from effectively crossing lipid bilayer membranes. (D) 2,4-DNP has been used as a very effective diet aid for the past 70 years. (E) None of the above is correct.

19. During β oxidation of fatty acids,_______ , is produced in peroxisomes but not in mitochondria.(A)acety1-coA(B) FADH2 (C)H2O(D) H2O2 (E) NADH

20. In humans, gluconeogenesis: (A) can result in the conversion of protein into blood glucose. (B) helps to reduce blood glucose after a carbohydrate-rich meal. (C) is activated by the hormone insulin (D) is essential in the conversion of fatty acids to glucose. (E) requires the enzyme hexokinase.

21. All are physiological changes initiated by glucagon except: (A) activation of glycogenolysis in liver. (B) stimulation of liver gluconeogenesis. (C) maintenance of steady-state levels of glucose in the blood stream. (D) activation of glycogenolysis in muscles. (E) All are true.