25. It is crucial that regulation occur at pyruvate dehydrogenase because:
(A) pyruvate kinase is reversible.
(B) lactate dehydrogenase is the only other enzyme to use pyruvate.
(C) the product acetyl-CoA is committed to oxidation in the citric acid cycle or fatty acid biosynthesis.
(D) alanine aminotransferase would use the pyruvate.
(E) All of the above.

21. When carbohydrate intake is low,______ are formed from acetate units to provide metabolic fuel for the ______and other tissue. (A) fatty acids； liver (B) ketone bodies； brain (C) ketone bodies； liver (D) amino acids； brain (E) sterols； heart

22. The_______ of pyruvate to acetyl-CoA is catalyzed by_______. (A) dehydration； pyruvate dehydration complex (B) decarboxylation； pyruvate dehydrogenase complex (C) decarboxylation； pyruvate decarboxylase (D) transacylation； pyruvate transacylase (E) None of the above.

23.The rate of oxidative phosphorylation in mitochondria is controlled prin (A) feedback inhibition by C02. (B) the availability of NADH from the TCA cycle. (C) the concentration of citrate. (D) the mass-action ratio of the ATD-ADP system. (E) the presence of thermogenin.

24._______and_______ are produced in the light reactions of photosynthesis which are used to convert _______to_______. (A) ATP； NADPH； carbon dioxide； sugar. (B) oxygen； ATP； NADPH； carbon dioxide (C) ATP； NADPt； carbon dioxide； sugar (D) oxygen； NADPH； ATP； sugar (E) NADPH； ATP； sugar； carbon dioxide

26. Given a Hill plot for protein X (shown in the figure). What is protein X's Hill coefficient? (A)0.5 (B)1 (C)2 (D) 3 (E) 4

27. What amino acids utilize chorismate for their biosynthetic ingredient? (A) Trp, Asp, Phe (B) Thr, Asn, Lys (C) Asp, Thr, Gln (D) Trp, Tyr, Phe (E) Met, Ile, Leu, Lys

複選題28. Regarding the binding energy generated from enzyme-substrate interactions, which statement is accurate? (A) It is insufficient to account for the substantial rate increases caused by enzymes. (B) It may be utilized to maintain two substrates in the ideal orientation for a reaction. (C) It originates from the formation of covalent bonds between the enzyme and substrate. (D) A large portion of it comes from covalent bonds between the enzyme and substrate. (E) The majority of it is expended in just attaching the substrate to the enzyme.

29.Which of the following is not involved in signal transduction by the B-adrenergic rece (A) Cyclic AMP synthesis (B) GTP hydrolysis (C) GTP-binding protein (D) Protein kinase (E) All of the above are involved.

30. Regulation of cholesterol biosynthesis:(A) involves transcriptional regulation but not covalent regulation. (B) is sensitive to insulin but not glucagon. (C) occurs in the short term primarily by regulating HMG-CoA reductase. (D) involves changes in the rate of biosynthesis of critical enzymes, but not changes in the rate of proteolysis of those enzymes. (E) All above are correct.

31. A marathon runner is engaged in a 20-mile run. During a 20-mile run, there is an increase in the rate at which acyl-CoA is taken up by the mitochondria and used by β-oxidation. Part of the increase can be explained by the increase fatty acid entering the cell and part is explained by all of the following except (A) Glucagon triggers the release of free fatty acids from adipose tissue to meet energy needs. (B) AMP-dependent protein kinase (AMPK) causes the phosphorylation of acetyl-CoA carboxylase. (C) Phosphorylation of acetyl-CoA carboxylase inhibits the production of malonyl-CoA. (D) The malonyl-CoA concentration drops and inhibition of carnitine-acyltransferase II is removed. (E) Much more acyl-carnitine is available to use the carnitine/acyl-carnitine transporter