26. Immobilized metal affinity chromatography (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

22 The standard reduction potentials (E'°) for the following half reactions are given. If you mixed succinate, fumarate, FAD, and FADH2 together, all at I M concentrations and in the presence of succinate dehydrogenase, which of the following would happen initially?(A) Fumarate and succinate would become oxidized; FAD and FADH2 would become reduced.(B) Fumarate would become reduced; FADH2 would become oxidized.(C) No reaction would occur because all reactants and products are already at their standard concentrations.(D) Succinate would become oxidized; FAD would become reduced.(E) Succinate would become oxidized; FADH2 would be unchanged because it is a cofactor.

23. Which of the following pairs is interconverted in the process of mutarotation?(A) D-glucose and D -fructose (B) D-glucose and D-galactose(C) D-glucose and D-glucosamine(D) D-glucose and L-glucose (E) a-D-glucose and β-D-glucose

24. The biochemical property of lectins that is the basis for most of their biological effects is their ability to bind to:(A) amphipathic molecules. (B) hydrophobic molecules. (C) specific lipids.(D) specific oligosaccharides. (E) specific peptides.

25. The citric acid cycle is considered part of acrobic metabolism even though oxygen does not appear explicitly in any reaction because:(A) it contains oxidative decarboxylation of isocitrate to succinyl-CoA.(B) it takes place in the mitochondrion.(C) the reoxidation of NADH and FADH2 leads to the production of considerable quantities of ATP.(D) it consumes H2O molecule.(E) the NADH and FADH2 produced are reoxidized in the electron transport chain linked to oxygen.

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) PLIVSQN (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.(E) When oxygen concentration is low, hemoglobin releases oxygen and binds H+.

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.

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 reaction Km becomes equivalent to:(A) kcat. (B) the [S] where Vo =  Vmax (C) the dissociation constant, Kd, for the ES complex.(D) the maximal velocity. (E) the turnover number.