1. Please choose the correct answer from the following descriptions:

1. Protein sectors are evolutionary units of three-dimensional structure.

2. The α-D-glucose and β-D-glucose interconvert in aqueous solution. 

3. Lectin is the exoskeleton of insects.

4. β-Keratin is Gly and Pro rich.

5. The pl of histidine is around 6.
(A) 1 and 2 are correct.
(B) 1, 3 and 4 are correct.
(C) 1 and 5 are correct.
(D) 2, 3 and 4 are correct.
(E) Only 4 and 5 are incorrect.

37. Post-translational modifications modulate a protein activity. To study the functional effect of a protein phosphoprylated at Ser/Thr, we generate a non-phosphorylatable mutant by changing to AlA What amino acids are used for creating a phosphomimetic mutant? (A) Asp and Glu (B) Lys and Arg (C) Leu and Ile (D) Gln and Arg (E) Tyr and Phe

38. Which description is incorrect for chromatin-immunoprecipitation (ChIP) experiment? (A) It is for DNA-protein interaction. (B) Formaldehyde is used to crosslink DNA-protein only. (C) The genomic DNA has to shear into smaller fragments by sonication or nuclease digestion. (D) The specific antibody against the interested protein is to immunoprecipitate cross-linked DNA fragments. (E) The precipitated DNA regions are examined by quantitative PCR.

39. Induced pluripotent stem (iPS) cells are a type of pluripotent stem cell that are obtained by reprogramming somatic cells through artificial expression of key transcription factors including OCT4, KLF-4, SOX2, and c-MYC. What is incorrect? (A) These transcription factors promote self-renew. (B) They suppress differentiation-related gene expression. (C) They alter DNA sequences to regulate gene expression. (D)DNA methylation inhibitor could facilitate iPS cell formation. (E) Histone deacetylase inhibitor could induce iPS cell formation.

40. We are studying a transcription factor. What is incorrect? (A) Its mRNA expression is determined by northern blot. (B) Its protein expression is monitored by western blot. (C) Its target gene promoter is cloned from a cDNA library. (D) The promoter is ligated with luciferase gene for reporter assay. (E) The electrophoretic mobility shift assay is performed to display DNA-protein interaction.

2. Which description is correct? (A) Lipopolysaccharide is a dominant feature of the outer membrane of the cell wall of gram-negative bacteria. (B) Trypsin could hydrolyze the "X-K" peptide bond. (C) Orthologous genes are presumed to have been derived by gene duplication followed by gradual changes in the sequences of both copies. (D) Collagen is full of α-helix structure and has Gly-X-Pro repeating sequence. (E) For naming the RS system, -CH2OH group has higher priority than -CHO group.

3. Please choose the correct answer from the following descriptions: (1) Comparing amino acids "C" and "S", there is only one atom difference. (2) For two-dimensional gel electrophoresis, proteins were separated according to their molecular weights, then further separated according to their pl values. (3) Using solid state peptide synthesis to synthesize the peptide "SMART", the synthesis sequence is T-R-A-M-S.  (4) Phenylisothiocyanate is used to do chemical fragmentation on methionine residues.  (5) Evolutionary relatedness can be inferred from sequence homology. Lysozyme and α-lactoalbumin are identical at 48 positions but their functions are not related. It is called "convergent evolution". (A) Only 1 and 3 are incorrect. (B) Only 2 and 4 are incorrect. (C) Only 2, 4 and 5 are incorrect. (D) Only 3 is correct. (E) Only 1 and 5 are correct.

4. Both water and glucose share an -OH that can serve as a substrate for a reaction with the terminal phosphate of ATP catalyzed by hexokinase. Glucose, however, is about a million times more reactive as a substrate than water. The best explanation is that: (A) glucose has more -OH groups per molecule than does water. (B) the larger glucose binds better to the enzyme； it induces a conformational change in hexokinase that brings active-site amino acids into position for catalysis. (C) the -OH group of water is attached to an inhibitory H atom, while the glucose -OH group is attached to C. (D) water and the second substrate, ATP, compete for the active site resulting in a competitive inhibition of the enzyme. (E) water normally will not reach the active site because it is hydrophobic.

5. When O2 binds to heme in hemoglobin, the ____ ion is drawn into the plane of the ____ causing a conformational change that is transmitted to adjacent subunits enhancing the ________ for additional O2 binding. (A) ； globin； planarity. (B) ； heme； folding. (C) ； globin； attraction. (D) ； porphyrin； affinity. (E) ； porphyrin； affinity.

6. BPG shifts the oxygen saturation curve of Hb to the ____ because BPG binds to ____ making Hb an O2 delivery system eminently suited for human. (A) right； deoxyHb. (B) right； oxyHb. (C) left； oxyHb. (D) left； deoxyHb. (E) none of the above.

7. In E. coli, rotation of the flagella is powered by: (A) phosphorylation of the motB protein by phosphoenolpyruvate. (B) a proton gradient across the plasma membrane of the bacterium. (C) the hydrolysis of ATP by the motB protein. (D) the hydrolysis of GTP by the flagella. (E) None of the above.