31. The T form (tense or taut form) of deoxyhemoglobin differs from oxyhemoglobin (the R form or relaxed form) by all   except  :
(A) covalent linkages between subunits.
(B) specific intrachain hydrogen bonds.
(C) between β-subunit salt links (ion-pair bonds).
(D) between a-subunits salt links (ion-pair bonds).
(E) intrachain salt bridges.

27. Which of the following statements about protein-ligand binding is   correct  ? (A) The (association constant) is equal to the concentration of ligand when all of the binding sites are occupied. (B) The is independent of such conditions as salt concentration and pH. (C) The larger the , the weaker the affinity. (D) The larger the , the smaller the (dissociation constant). (E) The larger the , the faster the binding.

28. Which of the following statements regarding enzyme regulation is   true  ? (A) Addition of an inhibitor to a V system results in kinetics similar to addition of a competitive inhibitor to a typical hyperbolic system. (B) Addition of an allosteric activator to a K system changes the plot of V vs. [S] from a sigmoidal curve to a more hyperbolic curve. (C) Allosteric effectors are always more powerful than covalent modification. (D) The T state of an enzyme generally has more activity than the R state. (E) None of the above are true.

29. In the enzyme catalyzed reaction sequence below, can the E-PO4- intermediate be predicted and why? (A) yes, the mechanism is a double-displacement reaction. (B) yes, the reaction fits the ping-pong model. (C) no, the reaction is random single-displacement. (D) no, the reaction is double-displacement. (E) no, the reaction is order single-displacement.

30. An enzyme-catalyzed reaction rate will be increased if the energy level of ES can be increased. Which of the following will   not   increase the energy level of ES? (A) destabilization of ES by strain caused by non-covalent interactions between E and S. (B) loss of entropy due to binding of E and S. (C) destabilization of ES by distortion. (D) destabilization of ES by electrostatic effects. (E) destabilization of ES by solvation.

32. The power stroke in muscle contraction is associated with: (A) the binding of ATP to ATPase. (B) the hydrolysis of ATP. (C) binding of myosin to actin. (D) addition of water for ATP hydrolysis. (E) the dissociation of ADP and Pi from the ATPase.

33. Which of the following four statements regarding glycolysis and gluconeogenesis is   correct  ? (1) Substrate-level phosphorylation occurs when conversion of1,3-bisphosphoglycerate to 3-phosphoglycerate occurs. (2) The only oxidative reaction in glycolysis is the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate. (3) The phosphofructokinase-1 catalyzes the glycolytic reaction step that is irreversible in gluconeogenesis. (4) If fructose-2,6-bisphosphate is low, glycolysis proceeds； if fructose-2,6-bisphosphate is high, gluconeogenesis proceeds. (A) (1), (2), and (4) are correct. (B) (1), (3), and (4) are correct. (C) (1), (2), and (3) are correct. (D) (2), (3), and (4) are correct. (E) All are correct.

34. Consider the reaction below, which of the following statement is   false  ? (A) When M is acetaldehyde, enzyme 1 is pyruvate decarboxylase. (B) When M is oxaloacetate, enzyme 1 is pyruvate carboxylase. (C) When M is phosphoenopyruvate, enzyme 2 is pyruvate kinase. (D) When M is malate, enzyme 2 is malic enzyme. (E) None of above is false.

35. Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is   correct  ? (A) The process occurs in the cytosolic compartment of the cell. (B) The methyl group is eliminated as CO2. (C) One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of acetate. (D) The pyruvate dehydrogenase complex uses all of the following as cofactors: , lipoic acid, pyridoxal phosphate (PLP), and FAD. (E) The reaction is so important to energy production that pyruvate dehydrogenase operates at full speed under all conditions.

36. 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) do none of the above.

37. Which one   directly   regulates fatty acid breakdown? (A) Succinyl CoA. (B) Myristoyl CoA. (C) Acetyl CoA. (D) Malonyl CoA. (E) Fatty acid synthase.