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.

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.

22. Which of the following is not required in the synthesis of fatty acids?(A) Acetyl-CoA (B) Biotin  (C) (D) Malonyl-CoA (E) NADH

23. When a cell with the pentose phosphate pathway has need for more pentose phosphates, but not for additional NADPH: (A) glucose-6-phosphate dehydrogenase is activated. (B) the oxidative and non-oxidative enzymes of the pentose phosphate pathway are active. (C) the non-oxidative enzymes produce pentose phosphates from fructose-6-phosphate- and glyceraldehyde-3-phosphate. (D) all enzymes of glycolysis and pentose phosphate pathway are active. (E) None of the above are true.

24. Which of the following descriptions is correct, regarding to the use of the enzyme glucose oxidase to determine the concentrations of glucose in blood? (A) Glucose is reduced to give glucono-6-lactone. (B) The reaction produces oxygen in company with glucono-6-lactone. (C) The reaction requires hydrogen peroxide as the oxidant. (D) Glucose is oxidized to give glucono-6-lactone. (E) Glucose is oxidized to give glucuronic acid

25. Certain nucleotide bases in DNA molecules are enzymatically methylated. In all known DNA methylation reactions the methyl group donor is: (A) S-adenosylmethionine. (B)  -methylenetetrahydrofolate. (C) N5-methyItetrahydrofolate. (D)(E) acetyl-CoA.

26. Which amino acid in the above table has a pKa that is very sensitive to the microenvironment and is often involved in enzyme catalysis? (A) I (B) II (C) III (D) IV (E) V

27. Which amino acid in the above table is able to form a salt bridge with a glutamate? (A) I (B) II (C) III (E) V (D) IV