Quiz 10 key - driven forward by loss of the product and the...

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Biochemistry 309, Winter 2010 20 points Quiz #10 NAME:_______________________________ TA:__________________ 1. For a reaction involving two substrates in which the enzyme forms a ternary complex with both substrates, draw a curve/line for the reaction at high [S2]. For the Lineweaver-Burk plot, label the intercepts with the Y axis and the X axis. (4 points) 2. Can K M be less than the K d for the enzyme-substrate interaction? (2 points) No. The Km is equal to or greater than Kd. 3. Assume the reaction above has a Keq of 9. For the left plot, if 10mM substrate is added to enzyme, draw the change of concentration of substrate as the reaction goes to equilibrium. For the right plot, if 10mM product is added to enzyme, draw the change of concentration of substrate as the reaction goes to equilibrium. (6 points) 4. If a reaction had a G ~ 0, but its product was consumed rapidly by an exergonic reaction, what would happen to the substrate concentration? (2 points) The substrate concentration would decrease because the reaction would be
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Unformatted text preview: driven forward by loss of the product and the drive toward equilibrium. 5. You carry out reactions with two different enzymes. You use 5nM enzyme and varying concentrations of two different substrates. Here are the data: Enzyme A Enzyme B Enzyme A Substrate #1 Substrate #2 Substrate #1 Substrate #2 V max 50 nM-1 s-1 300 nM-1 s-1 150 nM-1 s-1 150 nM-1 s-1 K M 50 nM 300 nM 30 nM 300 nM Which enzyme is more selective for one substrate vs the other? How specific is the more specific enzyme for one substrate vs the other? (6 points) We can determine the specificity for each reaction by comparing the Kcat/Km for each substrate. Because we have the same concentration of enzyme in all of the reactions, we can use Vmax/Km directly. Enzyme A is not specific; the Vmax/Km is the same for the two reactions. Enzyme B is specific for substrate #1; its Vmax/Km is 10x higher for substrate #1 than for substrate #2....
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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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