3987885451

3987885451 - Chemistry 3785 Fall Semester 2009 Third Hour...

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1 Chemistry 3785 Third Hour Exam Name KEY Fall Semester 2009 100 points Friday, Nov. 13, 2009 Exam A (Lucky Friday the 13 th ) Points Score Points Score I 45 IV 14 II 12 V 14 III 15 Total 100 I. (45) Multiple Choice. Circle the letter corresponding to the best choice. Three points each. 1. The reaction of X + Y Z has a Δ G °′ of -21.2 kJ mol -1 . One can predict that a. when X and Y are mixed the reaction will proceed rapidly toward the formation of Z. b. Z will rapidly break down to X and Y. c. at equilibrium the concentration of X will exceed the concentration of Y. d. at equilibrium the concentration of Z will be greater than the product [X][Y]. e. at equilibrium the product [X][Y] will be greater than 1. 2. The enthalpy change for the conversion A → B is 7 kJ mol -1 and the change in entropy is 20 J K -1 . We can say that a. the reaction is spontaneous at temperatures above 0 K. b. the reaction is nonspontaneous at all temperatures. c. the reaction is spontaneous at temperatures above 350 K. d. the reaction is spontaneous at all temperatures. e. both c and d are true. 3. The Δ G °′ of hydrolysis for the 1,3-bisphosphoglycerate reaction is -49.3 kJ mol -1 while the Δ G °′ of hydrolysis for ATP is -30.5 kJ mol -1 . For the reaction: 1,3-Bisphosphogylcerate + ADP → ATP + 3-phosphoglycerate the Δ G °′ of the reaction is ______ and indicates ______. a. -18.8 kJ mol -1 ; the reaction is spontaneous as written. b. -79.8 kJ mol -1 ; the reaction is spontaneous as written. c. -18.8 kJ mol -1 ; the reaction is not spontaneous as written. d. +79.8 kJ mol -1 ; the reaction is not spontaneous as written. e. +18.8 kJ mol -1 ; the reaction is spontaneous as written. 4. Gentle heating of ATCase at 60 ° C for 4 minutes denatures the regulatory subunits but does not affect the enzyme’s ability to synthesize carbamoyl aspartate. Under these conditions what statement is true ? a. ATCase no longer binds Asp cooperatively. b. Addition of CTP causes the rate vs. [S] curve to shift to the left. c. The enzyme is no longer sensitive to the levels of ATP. d. The rate of the reaction for the heat treated enzyme is about 50% that of the normal enzyme. e. both a and b are true.
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2 5. The K M for the reaction of chymotrypsin with N-acetylvaline ethyl ester is 8.8 × 10 -2 M, and the K M for the reaction of chymotrypsin with N-acetyltyrosine ethyl ester is 6.6 × 10 -4 M. We can say with certainty that a. chymotrypsin has a higher affinity for the ethyl ester of N-acetylvaline than for N-acetyltyrosine. b. chymotrypsin has a higher affinity for the ethyl ester of N-acetyltyrosine than for N-acetylvaline. c. N-acetyltyrosine ethyl ester gives a higher V max for chymotrypsin than does N-acetylvaline ethyl ester. d.
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3987885451 - Chemistry 3785 Fall Semester 2009 Third Hour...

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