3943657751 - Chemistry 3785 Fall Semester 2009 Second Hour...

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1 Chemistry 3785 Second Hour Exam Name KEY Fall Semester 2009 100 points Wed. Oct. 14, 2009 Exam A Points Score Points Score I 54 IV 10 II 12 V 12 III 12 Total 100 I. (54) Multiple Choice. Circle the letter corresponding to the best choice. Three points each. 1. Which of the following statements is not true about enzymes? a. Most enzymes catalyze reactions in both the forward and reverse direction. b. Enzymes alter the equilibrium constant thereby significantly increasing the rate of reaction. c. Enzymes typically act under much milder conditions of temperature and pH than chemical catalysts. d. Enzymes are very specific for their substrates. e. Enzymes lower the free energy for the transition state. 2. Cofactors which readily diffuse in and out of the active site are known as a. prosthetic groups b. coenzymes c. cosubstrates d. metal ion cofactors e. holoenzymes 3. Carboxypeptidase A catalyzes its reaction with a rate enhancement of 1.9 × 10 11 . How much does carboxypeptidase A decrease the free energy of activation of its reaction at 25 ° C? a. 64.3 kJ mol -1 b. 6.22 kJ mol -1 c. 2.79 × 10 4 kJ mol -1 d. 6.43 × 10 4 kJ mol -1 e. 2.53 kJ mol -1 4. Which of the following amino acid residues could not participate in general acid or base catalysis? a. His b. Arg c. Tyr d. Asp e. both b and c 5. In the proposed mechanism for chymotrypsin, His 57 a. acts as a general base catalyst by accepting a proton from the hydroxyl group of Ser 195. b. acts as a general acid catalyst by donating a proton to the scissile peptide bond. c. hydrogen bonds to the oxide anion of the tetrahedral intermediate. d. all the above e. only a and b
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2 6. What type of catalytic mechanism is not part of the action of serine proteases? a. stabilization of the transition state b. catalysis through proximity and orientation effects c. general base catalysis d. metal ion catalysis e. both b and d 7. The structure of L-glucose is a. b. c. d. e. 8. Which of the following is an anomeric pair? a. D-glucose and D-fructose b. D-glucose and L-fructose c. α -D-galactose and α -L-galactose d. β -D-fructose and α -D-fructose e. β -D-glucose and β -D-galactose 9. What is the correct Haworth structure for the α anomer of D-galactopyranose? a. b. c. d. e. 10. D-Fructose is one of ____ possible stereoisomers of a ketohexose? a. 2 b. 4 c. 8 d. 16 e. 32 11. Raffinose is a trisaccharide and a minor constituent in sugar beets. Its structure is shown to the right. What statement is not true? a. Raffinose consists of the three monosaccharides galactose, glucose, and fructose. b.
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This note was uploaded on 11/24/2011 for the course BIO 400 taught by Professor Raganbower during the Winter '10 term at Drexel.

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3943657751 - Chemistry 3785 Fall Semester 2009 Second Hour...

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