33. Which of these statements about enzyme-catalyzed reactions is   false  ?
(A) At saturating levels of substrate, the rate of an enzyme-catalyzed reaction is proportional to the enzyme concentration.
(B) If enough substrate is added, the normal Vmax of a reaction can be attained even in the presence of a competitive inhibitor.
(C) The rate of a reaction decreases steadily with time as substrate is depleted.
(D) The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but the equilibrium constant is more favorable in the enzyme-catalyzed reaction.
(E) The Michaelis-Menten constant equals the [S] at which V = 1/2

29. The following figure describes the torsion angle of the residue i in a protein. What do the following figures tell you? (A) The left one is ψ angle +90 degree. (B) The right one is φ angle +45 degree. (C) The left one is φ angle +90 degree. (D) The right one is φ angle +60 degree. (E) The left one is φ angle -90 degree.

30. A protein mixture contains protein A, B, C. Protein A: homodimer Mr = 180,000, pI 5； Protein B: Mr = 12,000, pI 7； Protein C: M____r = 150,000, pI 9 Joseph says: When I used SDS-PAGE to separate these three proteins. The sequence of the protein bands shown in gel from top to bottom is A-C-B. Steve says: When I used SDS-PAGE to separate these three proteins. The sequence of the protein bands shown in gel from top to bottom is B-A-C Jacky says: When I dissolved the protein mixture in 20 mM phosphate buffer (pH 7) and loaded it to a cation exchange column equilibrated with the same buffer. Only protein C could bind to the column matrix Simon says: When I dissolved the protein mixture in 20 mM phosphate buffer (pH 8) and loaded it to an anion exchange column equilibrated with the same buffer. Only protein C could bind to the column matrix Clarence says: When I dissolved the protein mixture in 150 mM phosphate buffer (pH 7) and used a gel filtration column to separate them, the elution sequence is B→C→A. Rita says: When I dissolved the protein mixture in 150 mM phosphate buffer (pH 7) and used a gel filtration column to separate them, the elution sequence is A→C→B. Lily says: When I dissolved the protein mixture in 150 mM phosphate buffer (pH 7) and used a gel filtration column to separate them, the elution sequence is C→A→B. Who are correct? (A) Joseph, Simon, and Clarence. (D) Simon and Clarence. (B) Rita and Jacky. (E) Joseph, Jacky, and Rita. (C) Steve, Jacky, and Lily.

31. There are three peptides, A, B, and C. Peptide A sequence is DSQWMKLGIV. Peptide B sequence is KLHPPGTI. Peptide C sequence is EETAIRR. Amelia says: The pI value of peptide A should be near 9. David says: The pI value of peptide C is higher than peptide B. Bret says: The pI value of peptide B should be near 6. Sandy says: The pI value of peptide B is higher than peptide A. Who is correct? (A) Amelia. (B) All are incorrect. (C) David. (D) Bret. (E) Sandy.

32. A small molecule that increases the activity of an enzyme by binding to a site other than the catalytic site is termed a(n): (A) allosteric activator. (B) alternative inhibitor. (C) competitive activator. (D) stereospecific agent. (E) transition-state analog.

34. When every enzyme molecule in the reaction mixture has its substrate-binding site occupied by substrate, the kinetics become _____ -order, and the velocity is _____. (A)(B) (C)(D) (E)

35. All are properties of regulatory enzymes   except  : (A) pathway end-products may act as allosteric inhibitors. (B) v vs [S] plots are sigmoid- or S-shaped. (C) monomeric enzymes with a single regulated active site. (D) substrate binding is cooperative. (E) may be stimulated by allosteric activators.

36. Which of the following cofactors is required for the conversion of succinate to fumarate in the citric acid cycle? (A) ATP. (B) Biotin. (C) (D) (E) FAD.

37. Which one of the following enzymatic activities would be decreased by thiamine deficiency? (A) Fumarase. (B) Isocitrate dehydrogenase. (C) Malate dehydrogenase. (D) Succinate dehydrogenase. (E) α-Ketoglutarate dehydrogenase complex.

38. The conversion of 1 mole of fructose 1,6-bisphosphate to 2 mole of pyruvate by the glycolytic pathway results in a net formation of: (A) 1 mole of NADH and 1 mole of ATP. (B) 2 mole of NAD⁺ and 4 mole of ATP. (C) 1 mole of NAD⁺ and 2 mole of ATP. (D) 2 mole of NADH and 4 mole of ATP. (E) 2 mole of NADH and 2 mole of ATP.

39. Which one of the following statements is true? 1. In glycolysis, ATP is synthesized by both substrate-level and oxidative phosphorylation. 2. Fructose-1,6-bisphosphate is an allosteric factor for controlling by phosphofructokinase. 3. In the glyceraldehyde-3-phosphate dehydrogenase reaction, the amino acid cysteine is important in adding a second phosphate to glyceraldehyde phosphate. 4. During anaerobic metabolism in red blood cells, the carbons of glucose end up in lactic acid. 5. Phosphofructokinase and pyruvate kinase both are tetrameric. (A) All are true. (B) 1 and 4 are not true. (C) 5 is not true. (D) 1, 3 and 5 are not true. (E) 2 and 4 are not true.