30. Most covalent catalysis is carried out by enzymes using a:
(A) ping-pong kinetic mechanism.
(B) sequential bisubstrate kinetic mechanism.
(C) random bisubstrate kinetic mechanism.
(D) simple unimolecular kinetic mechanism.
(E) competition mechanism.

26. Immobilized metal affinity chromatograpby (IMAC) is an important tool for recombinant protein purifications. Nickel (Ni2+) nitriloacetic acid (Ni-NTA) agarose is a commonly used affinity resin for IMAC. Which of the following peptide motif is often engineered to the target protein for IMAC-based purifications? (A) Polyalanine (B) Polyhistidine (C) Polylysine (D) Polyproline (E) Polyglycine

27. N-linked glycosylation is a common form of post-translational modification. Which of the following peptides is likely to be N-glycosylated? (A) ATQPCSN (B) SMNASTK (C) PLIVSON (D) NPTGGS (E) WANLIYT

28. PNGase F is the most effective enzyme for removing N-linked oligosaccharides from glycoproteins/glycopeptides. The glycan removal is accompanied by deamidation of the asparagine side-chain to which the N-linked oligosaccharides are attached. Which of the following statements is false about the target protein after PNGase F treatment? (A) The molecular weight of the target protein will be reduced. (B) The extinction coefficient at 280 nm of the target protein will be unchanged. (C) The primary structure of the target protein will be the same. (D) The target protein will gain additional aspartic acid residues. (E) The isoelectric point of the target protein will be reduced.

29. Which of the following statements about the Bohr effect regarding hemoglobin's oxygen binding capacity is false? (A) Hemoglobin's oxygen binding affinity is inversely proportional to the acidity of the blood (B) Hemoglobin's oxygen binding affinity is inversely proportional to the concentration of carbon dioxide in the blood (C) Carbonic anhydrase helps increase the concentration of carbonate in the blood. (D) Modification of the amino-terminus of hemoglobin by carbon dioxide into a carbamino-terminus will increase oxygen binding affinity of hemoglobin. When oxygen concentration is low, hemoglobin releases oxygen and binds Ht.

31. Steroid hormone response elements (HREs) are_____，which, when bound to_______， alter gene expression at the level of_______. (A)intron sequences； activated hormone receptor； translation (B) nuclear proteins； hormone； transcription (C) plasma membrane proteins； hormone； transcription (D) sequences in DNA； receptor-hormone complex； replication (E) sequences in DNA； receptor-hormone complex； transcription

32. For enzymes in which the slowest (rate-limiting) step is the reactionKm becomes equivalent to: (A) kcat. (B) the [S] where V0 = Vmax. (C) the dissociation constant, Kd, for the ES complex. (D) the maximal velocity. (E) the turnover number.

33. Which of the following statements about glycolysis is correct?(1) Conversion of glucose to glyceraldehyde-3-phosphate is an endergonic reaction.(2) In the conversion of glucose-6-phosphate to fructose-6-phosphate, the C-1 aldehyde of glucose-6-phosphate is reduced to a hydroxyl group.(3) Conversion of dihyroxyacetone phosphate to glyceraldehyde-3-phosphate is an isomerization reaction. (A) 1 and 2 (B) 1 and 3 (C) 2 and 3 (D) None of above is correct. (E) All of above are correct.

34. Which of the following statements about the following reaction is correct?Citrate + COA-SH + ATP → Acetyl-CoA + Oxaloacetate + ADP + Pi(1) The reaction is catalyzed by ATP citrate lyase.(2) Formation of acetyl-CoA in this reaction provides the starting materials for lipid metabolism.(3) Formation of oxaloacetate in this reaction provides an indirect means for the production of the NADPH for lipid metabolism. (A) 1 and 2 are correct. (B) 1 and 3 are correct. (C) 2 and 3 are correct. (D) All of above are correct. (E) None of above is correct.

35. Concerning the pathway for ketone body synthesis, all of the following make sense except (A) Three acetyl-CoA molecules can become HMG-CoA. (B) HMG-CoA is used for cholesterol and ketone body synthesis. (C) HMG-CoA lyase produces acetoacetate and acetyl-CoA. (D) Acetoacetate is oxidized to beta-bydroxybutyrate and acetone. (E) The rate of ketone body production is proportional to the excess acety! CoA in the mitochondria.

36. Which of the following statement(s) is correct regarding the regulation of fatty acid synthesis and breakdown?(1) Malonyl-CoA is the key repressor for fatty acid degradation due to the inhibition of fatty acid entry into mitochondria.(2) Insulin signaling triggers the dephosphory lation of acetyl-CoA carboxylase to synthesize malonyl-CoA. (3) The reaction catalyzed by fatty acid synthase is the rate-limiting step in the biosynthesis of fatty acids. (B) 2 and 3 (C) 1 and 3 (E) All of above are correct. (A) 1 and 2 (D)2 only