16. Some hormones are derived from amino acids； for example, catecholamines are derived from______ while serotonin is derived from______ . 
(A) tyrosine； tryptophan
(B) tryptophan； lysine
(C) tyrosine； histidine
(D) tryptophan； arginine
(E) histidine； lysine

12. Starch is a high molecular weight polymer of D-glucose in α1→4 linkage. It is synthesized by starch synthase, which transfers glucose residues from _______to preexisting starch molecules. (A) glucose 6-phosphate (B) ATP-glucose (C) ADP-glucose (D) sucrose (E) glucose 1-phosphate

13. Which of the following descriptions about the melting temperatures of the fatty acids are correct? (A) 1,3, and 4 only (B) 3,4, and 6 only (C) 2,3, and 5 only (D) 3 and 6 only (E) 1 and 4 only

14. Oxidative stress results when the superoxide anion () is formed as a side reaction of mitochondrial electron transport. This oxygen anion radical is made nontoxic by the action of enzymes in the mitochondrial matrix. Which of the following enzymes acts on two , converting then to one molecule of water and one of H2O2? (A) Glutathione reductase. (B) Superoxide hydroxylase. (C) Glutathione peroxidase. (D) Glutathione. (E) Superoxide dismutase.

15. The relative concentrations of ATP and ADP control the celiular rates of: (A)glycolysis. (B) oxidative phosphorylation. (C) pyruvate oxidation. (D) the citric acid cycle. (E) All of the above.

17. Which of the following is not true during fasting? (A) During fasting, the liver maintains blood glucose levels. (B) Amino acids from muscle protein are a major carbon source for the production of glucose by the pathway of gluconeogenesis. (C) As amino acid carbons are converted to glucose, the nitrogens are converted to urea. Thus, the urinary excretion of urea is high during fasting. (D) As fasting progresses, however, the brain begins to use ketone bodies, sparing blood glucose. (E) Only muscle proteins are mobilized for energy requirement.

18. Which of the following is not involved in triggering insulin from beta-cells release in response to glucose? (A) Reduced eflux through ATP-gated K*-channels (B) Increased concentrations of ATP (C) cAMP-dependent phosphorylation of lipase (D) Phosphorylation of glucose to glucose-6-phosphatc (E) Increased Cazt levels

19. Which contain(s) a phosphoanhydride bond? (A) DNA(B)RNA (C) protein (D) ATP (E) Both DNA and RNA

20. Supercoiling of DNA: (A) is not observed in prokaryotes. (B) requires the action of topoisomerase enzymes. (C) does not require ATP. (D) is not observed in eukaryotes. (E) None of the above is true.

21. What is the main damaging effect of UV radiation on DNA? (A) Depurination (B) Deamination(C)Formation of thymine dimers (D) Single strand break (E) Dehydration

22. The binding of lac repressor to DNA could be considered to be analogous to: (A) competitive inhibition of an enzyme. (B) mixed-type inhibition of an enzyme. (C) uncompetitive inhibition of an enzyme. (D) allosteric effects in enzyme regulation. (E) None of the above