複選題
76. Which of the following is related to the function of proofreading step?
(A) Riboswitch
(B) EF-G in protein synthesis
(C) Synthesis of aminoacyl-tRNA
(D) RNA polymerase
(E) None of the above

72. In the erythrocyte, glycolysis produces ________that is further metabolized to ________. (A) lactate; acetyl-CoA (B) lactate; pyruvate (C) pyruvate; acetyl-CoA (D) pyruvate; lactate (E) pyruvate; oxaloacetate

73. What role does AP endonuclease have in the base-excision repair system? (A) It removes the damaged base from the nucleic acid. (B) It cleaves the phosphodiester backbone after base removal. (C) It removes nucleotides from the broken strand of the nucleic acid. (D) It adds new nucleotides to replace the excised ones. (E) It creates a new phosphodiester bond to repair the backbone.

74. Restriction-modification systems: (A) exist in all organisms as a protection against foreign DNA invasion. (B) include a site-specific exonuclease to degrade foreign DNA. (C) modify DNA by acetylation. (D) include a DNA methylase and an endonuclease. (E) include three types of endonuclease all of which cleave within a specific DNA target sequence.

75. DNA polymerase I synthesizes new DNA with very high fidelity, due to its ________. (A) high processivity (B) 3'→5' exonuclease activity (C) helicase association with the primase (D) 5'→3' exonuclease activity (E) all of the above

77. Which of the following is least related with RNA interference? (A) RISC (B) Drosha (C) Dicer (D) miRNA (E) snRNA

78. What acts as the nucleophile in the mechanism of nucleotide addition by RNA polymerase? (A) The 5' phosphate of an incoming nucleotide (B) A water molecule (C) A 5' hydroxyl of the template DNA (D) A 3' hydroxyl from the RNA being extended (E) An aspartate in the active site

79. What type of mutation causes conditions such as Huntington’s disease and Fragile X syndrome? (A) An excess of trinucleotide repeats in a protein-coding gene (B) A mutation in the p53 tumor suppressor (C) A mutation in a cyclin-dependent protein kinase (D) A mutation in the retinoblastoma gene (E) A mutation in caspase-activated DNase

80. The photosynthetic electron transport system includes the transmembrane complexes PSI, PSII and ________. (A) PSIII (B) cytochrome a3 (C) cytochrome (D) cytochrome c(E) proton translocating ATP synthase

81. The analysis of enzyme kinetics using steady-state methods: (A) assumes d[ES]/dt = 0. (B) provides an accurate description of the reactions at all times. (C) can only be used if the product does not inhibit the enzyme. (D) cannot be applied when inhibitors are present. (E) can only be used if the substrate does not inhibit the enzyme.

82. Which of these statements about enzyme-catalyzed reactions is false? (A) The Vmax of a reaction can be attained at saturated concentration of substrate, even in the presence of a competitive inhibitor. (B) At saturating levels of substrate, the rate of an enzyme-catalyzed reaction is proportional to the enzyme concentration. (C) The rate of a reaction decreases steadily with time as substrate is depleted. (D) The Michaelis-Menten constant Km equals the [S] at which v = 1/2 Vmax. (E) 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.