Final Questions

Final Questions - BIS 102 Prof C Gasser 105 1 For the...

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BIS 102, Prof. C. Gasser 105 1. For the following questions mark an "X" in the blank next to the most correct answer to the question (one answer for each question). a). (4) An important class of enzyme inhibitors are transition state analogs. These inhibitors resemble the high-energy transition state that is stabilized by an enzyme. What class of inhibitor would a transition state analog most likely fall into? Tetrahedral. Uncompetitive. Allosteric. Non-competitive. X Competitive. (it would bind to the active site and prevent S binding) b) (4) A benefit of measuring the initial rate of an enzyme catalyzed reaction, V i , is that at the beginning of a reaction: X Changes in [S] are negligible, so [S] can be treated as a constant. [ES] can be measured accurately. V i = V max Changes in K m are negligible, so K m can be treated as a constant. Varying [S] has no effect on V i . c) (4) A homotetrameric enzyme, E, has four identical binding sites for substrate S, and exhibits positive cooperative binding of substrate S. Which of the following is least likely to be true of E? There are disulfide bonds between the subunits of E. The reaction catalyzed by E exhibits a sigmoidal dependence on [S]. X The K m of E for S is increased by S binding. Other factors bind to and regulate the activity of E. V max = k cat [E t ].
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BIS 102, Prof. C. Gasser 106 d) (4) For the enzyme catalyzed reaction: E + S ES E + P k 1 k -1 k -2 k cat The expression that best defines the Michaelis-Menten constant (K m ) for this reaction using the initial rates and steady-state assumptions (as used in class) is: K m = [E]·[S] [ES] K m = k -1 k 1 K m = d[P] dt K m = k -1 + k 1 k cat X K m = k -1 + k cat k 1 2. An enzyme, E, catalyzes the reaction A B leading to a 10 9 -fold increase in the reaction rate. Relative to the uncatalyzed reaction, what effect does the enzyme have on each of the following? Use "U" for unchanged, "I" for increased, "D" for decreased, and "N" for need more information. (3 pts. each). [B] at equilibrium U G (activation energy) for the reaction A B D H for the reaction A B U G°' for the reaction B A U G for the reaction A B if [A] < [B] U
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BIS 102, Prof. C. Gasser 107 3. The active ingredients of some chemical weapons are inhibitors of the enzyme acetylcholinesterase (ACHE). A U. C. researcher was provided with blood samples (identified with codes, “UPI, and “AP”) from two groups of individuals and was asked to determine if either group had been exposed to ACHE inhibitors. The researcher was also provided with blood from people known not to have been exposed (“Control”). Protein gels showed that the amount of ACHE protein did not differ between the three blood samples. Because the groups were fairly large, there was little possibility that any sample would contain a significant level of any mutant form of ACHE. Measurement of the activity of ACHE in the blood samples at various substrate concentrations produced linear Lineweaver- Burk plots that were used to determine the values in the table below.
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Final Questions - BIS 102 Prof C Gasser 105 1 For the...

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