76. Which of the following enzymes are aspartate protease ? ① Subtilisin； ② Cathepsin D； ③ HIV-protease； ④ Thrombin； ⑤ Pepsin
(A) ①,②,③
(B) ①,②,④
(C) ①,②,⑤
(D) ②,③,④
(E) ②,③,⑤

72. Which of the following statements about lac operon is CORRECT? ① The repressor is the protein product of lac Z gene. ② The lac operon can be turned on by β-galactoside. ③ Repressor binds to the operator and blocks the binding of RNA polymerase to promoter. ④ Isopropyl-β-D-thiogalactoside can bind to Lac repressor to turn on protein expression. ⑤ In the lac operon model, the genes within the operon will be expressed if lactose is present in E. coli. (A) ①,②,③ (B) ①,②,④ (C) ②,③,④ (D) ③,④,⑤ (E) ②,③,④,⑤

73. Which of the following statements about glutathione are CORRECT? ① Glutathione is an antioxidant. ② Glutathione is a tetrapeptide. ③ Glutathione is not involved in detoxification of xenobiotics. ④ The biosynthsis of glutathione synthesis occurs as a part of γ-glutamyl cycle. ⑤ Oxidized glutathione is reduced by glutathione reductase. (A) ①,②,③ (B) ①,③,④ (C) ①,④,⑤ (D) ②,③,④ (E) ①,②,⑤

74. Which of the following statements about citric acid cycle is FALSE? (A) The first reaction is to synthesize citric acid. (B) In addition to CTP, NADH and QH2 are also produced in citric acid cycle. (C) The acetyl group of acetyl-CoA is released in the form of CO2 when it enters citric acid cycle. (D) The product of the last step, oxaloacetate, is also the reactant of the first step. (E) It occurs in mitochondrial matrix.

75. Which of the following statements about amino acids is CORRECT? ① Methionine is sulfurcontaining amino acids. ② The UV absorbance of phenylalanine at 280 nm is lower than that of tyrosine. ③ Disulfide bond can be reduced by performic acid. ④ The side chain of histidine is an imidazole ring. ⑤ The pI value of arginine is lower than that of lysine. (A) ①,②,③ (B) ①,③,④ (C) ②,③,④ (D) ①,②,④ (E) ②,③,⑤

77. Which of the following statements for the structure of proteins are CORRECT? ① A bond between amino acids is peptide bond. ② Disulfide bonds in proteins are formed by serine. ③ The amino acid sequence is the primary structure of proteins. ④ The coil-coiled motif is the tertiary structure of proteins. ⑤ The quaternary structure of proteins contains two or more polypeptide chains. (A) ①,③,⑤ (B) ②,③,④ (C) ②,③,⑤ (D) ①,③,④ (E) ①,②,③

78. In order to infect cells, the hemagglutinin of the influenza virus binds with ______ in the cell surface glycoproteins or glycolipids. (A) sialic acid (B) gluconic acid (C) N-acetylmuramic acid (D) uronic acid (E) muramic acid

79. In electron-transport chain, the transferring sequence of the electrons passing from NADH to oxygen is: (A) Complex I→Complex III→Complex IV→Complex V (B) Complex I→Complex II→Complex III→cytochrome c→Complex IV (C) Complex I→Q→Complex II→Complex III→cytochrome c→Complex IV (D) Complex I→Complex II →Complex III →Complex IV (E) Complex I→Q→Complex III→cytochrome c→Complex IV

80. Which of the following BEST explains the "wobble" hypothesis proposed by Francis Crick? (A) The genetic code is degenerate in that most amino acids have more than one codon. (B) The genetic code is ambiguous in that each codon can specify more than one amino acid. (C) The anticodon can pair with any part of the corresponding codon. (D) The 5'-base of the anticodon can make non Watson-Crick hydrogen bonds with several different bases at the 3'-position of the codon. (E) Inosine can pair up with C, G, or U.

81. Phospholipids show asymmetric distribution on membrane of erythrocytes. Which of the following phospholipids prefer to distribute on the outer leaflet of erythrocyte membrane? ① phosphatidylcholine； ② phosphatidylserine； ③ phosphatidylinositol； ④ sphingomyelin； ⑤ phosphatidylethanolamine (A) ①,② (B) ①,③ (C) ①,④ (D) ②,③ (E) ②,⑤

82. Mammalian phosphofructokinase, the major flux-controlling enzyme of glycolysis, is regulated by ① allosteric activator, fructose 2, 6-bisphosphate； ② allosteric inhibitor, ATP； ③ allosteric activator, AMP； ④ allosteric inhibitor, ADP； ⑤ allosteric activator, Citrate (A) ①,②,③ (B) ①,③,④ (C) ①,②,⑤ (D) ①,③,⑤ (E) ①,④,⑤