75. Which of the following is not correct concerning cooperative binding of a ligand to a protein?
(A) It is usually a form of allosteric interaction.
(B) It is usually associated with proteins with multiple subunits.
(C) It rarely occurs in enzymes.
(D) It results in a nonlinear Hill Plot.
(E) It results in a sigmoidal binding curve.

71.When the amino group has been removed from an amino acid, the carbon skeleton or a-keto acid may be used in many different ways. Which of the following is NOT a possible fate for the carbon skeleton? (A) conversion to glucose (B) oxidation for energy (C) synthesis of fat (D) synthesis of creatine (E) synthesis of ketones

72. Which process is NOT a source of ammonia in the body? (A) urea formation in the liver (B) deamination of amide groups from glutamine (C) degradation of pyrimidines (D) bacterial lysis of urea and amino acids in the GI tract (E) complete oxidation of amino acids

73 Reduction of the carbonyI group on a sugar rise to the class of polyhydroxy compounds called alditols. Important naturally occurring ones are erythritol, D-mannitol, and D-glucitol, often called sorbitol. When sorbitol accumulates in the lens of the eye of a person with diabetes, it can lead to the formation  of________.(A) Glaucoma(B) Amblyopia (C) Cataract (D) Strabismus (E) None of the above

74. Enzyme kinetics provide the values of the Michaelis constant KM and the turnover number Kcat. Which of the following statements is true? (A) KM indicates the substrate concentration at which the reaction rate is Vmax (B) KM measures the rate of the catalytic process (C) KM indicates the substrate binding affinity； the smaller KM indicates the higher substrate binding affinity (D) In enzyme inhibition study, a competitive inhibitor decreases the apparent KM (E) All of the above 

76. Which of the following is not involved in the specificity of signal transduction? (A) Interactions between receptor and signal molecules (B) Location of receptor molecules (C) Structure of receptor molecules (D) Structure of signal molecules (E) Transmembrane transport of signal molecules by receptor molecules

77. The technique known as yeast two hybrid analysis for detecting interacting gene products depend on: (A) activation of DNA polymerase by the nearby binding of hybridizing protein complexes. (B) direct binding of a Gal4p activation domain to a DNA sequence in the promoter region. (C) having a promoter that responds directly to one of the two proteins whose interactions is being measured. (D) hybridization of DNA segments corresponding to the two genes being examined. (E) stimulation of transcription by interaction of two Gal4p domains via fused protein sequences.

78. In DNA sequencing by the Sanger (dideoxy) method: (A) radioactive dideoxy ATP is included in each of four reaction mixtures before enzymatic synthesis of complementary strands. (B) specific enzymes are used to cut the newly synthesized DNA into small pieces, which are then separated by electrophoresis. (C) the dideoxynucleotides must be present at high levels to obtain long stretches of DNA sequence. (D) the role of the dideoxy CTP is to occasionally terminate enzymatic synthesis of DNA where Gs occur in the template strands. (E) the template DNA strand is radioactive.

79. Which of the following compounds would be most closely associated with the intermediate common to glycogenesis and glycogenolysis? (A) 6-phosphogluconate (B) Glucose-1-phosphate (C) Glucose-6-phosphate (D) Fructosc-6-phosphate (E) Dihydroxyacetone phosphate

80. Which of the following enzymes and pathways are correctly matched? (A) Phospholipase D and prostaglandin synthesis (B) HMG-CoA reductase and ketone body synthesis (C) Cyclooxygenase and thromboxane synthesis (D) Ethanolamine kinase and phosphatidylcholine synthesis (E) Phospholipase A2 and ceramide synthesis.

81. Which of the following is the major site of expression for the monosaccharide transporter GLUT1? (A) erythrocytes, CNS, blood brain barrier (B) liver, pancreaticβ-cells, small intestine (C) neurons, testis, placenta (D) skeletal muscle, adipose tissue (E) small intestine, kidney, skeletal muscle, adipose tissue