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.

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

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.

83. Which of the polypeptide is most likely to form a collagen structure? (A) IQEVERDIQEVERDIQEVERD (B) SRAGNRKIVLETW (C) TEDNFPAGKSILF (D) GAPGSPGPSGAP (E) NKASVEMAIRNGS

84. Which of the following is false regrading 2,3-bisphosphoglycerate (BPG)? (A) It binds at a distance from the heme groups of hemoglobin. (B) It binds with lower affinity to fetal hemoglobin than to adult hemoglobin. (C) It increases the affinity of hemoglobin for oxygen. (D) It is an allosteric modulator of hemoglobin. (E) It is normally found associated with the hemoglobin extracted from red blood cells.

85. Proline residues are infrequently found in ________due to their ________. (A) helices; decreased ability to serve as hydrogen-bond donors (B) helices; large positive charge that disrupts the repeating structure (C) sheets; decreased ability to serve as hydrogen-bond donors (D) sheets; large positive charge that disrupts the repeating structure (E) turns; decreased flexibility as an amino acid

86. When oxygen is bound to myoglobin, the amino acid ________ is complexed to the iron ion of the heme group while ________ forms a hydrogen bond to the oxygen. (A) cysteine; serine (B) cysteine; histidine (C) serine; cysteine (D) histidine; histidine (E) histidine; cysteine

87. Which of the following is associated for determining the dihedral angle (phi) of the peptide bonds? (A) CO-NH-Cα-CO (B) NH-Cα-CO-NH (C) Cα-CO-NH-Cα (D) HN-Cα-CO-NH (E) Hα-CO-NH-Hα