Quiz 9key (1) - Explain. (2 points) The Km is a constant...

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Biochemistry 309, Winter 2010 20 points Quiz #9 NAME:_______________________________ TA:__________________ 1. For the following reaction scheme, indicate which species interacts with a competitive inhibitor (label C) or an uncompetitive inhibitor (label U). (3 points) E + S ES E + P C U 2. When the rate of a reaction is less than Vmax, is the Kcat slower? Explain. (3 points) No. The Kcat is a constant. When the reaction is proceeding at less than Vmax, it is because not all the enzyme is in the ES complex. 5. If a reaction rate is at Vmax, how would the V o be changed by adding more substrate? Explain. (2 points) The concentration is ES is limited by enzyme concentration and would not be changed by adding more substrate. How would the V o be changed by adding more enzyme? Explain. (2 points) The [ES] would increase and the reaction rate would increase. How would the Km of the reaction be affected by adding more substrate?
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Unformatted text preview: Explain. (2 points) The Km is a constant and would not be affected by the concentration of substrate. How would the Km of the reaction be affected by adding more enzyme? Explain. (2 points) The Km is a constant and would not be affected by the concentration of enzyme. 3. An enzyme has a K cat /K M of 10 6 M-1 s-1 . In a reaction with 1nM enzyme and 10 M substrate if the enzymes K M for substrate is 100 M, What is Vmax? (2 points) Vmax = [E] Kcat Kcat = 10 6 x 10-4 = 100 s-1 Vmax = 10-9 M x 100s-1 = 10-7 Ms-1 What is the reaction rate at this concentration of substrate? (2 points) V = Vmax [S]/Km + [S] = (10-7 Ms-1 x 10-5 M)/(10-4 M + 10-5 M) = 10-12 M 2 s-1 /1.1 x 10-4 M = 9 x 10-9 Ms-1 What fraction of the substrate is bound to enzyme under these conditions? (2 points) Concentration of ES = [E] x (Vo/Vmax) = 10-9 M x (9 x 10-9 Ms-1 /10-7 Ms-1 ) = 9 x 10-11 M Fraction of substrate = 0.9 x 10-11 M/10-5 M = 9 x 10-6...
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This note was uploaded on 02/16/2012 for the course BIOL_SCI 309 taught by Professor Somebody during the Winter '10 term at Northwestern.

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