ExamIII_Fall2007_key

# ExamIII_Fall2007_key - 1 Fall 2007 EXAM III Name Dr...

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Unformatted text preview: 1 Fall 2007 EXAM III Name:__________________ Dr. Marcotte CH339K UT EID: ________________ ** SHOW WORK FOR COMPUTATIONAL PROBLEMS OR NO CREDIT!! ** (8) 1. For a reaction that can take place with or without catalysis by an enzyme, what would be the effect of the enzyme on: (answer with increase , decrease , or no change ) (a) standard free energy change of the reaction? ____ no change _________ (b) activation energy of the reaction? ____ decrease __________ (c) initial velocity of the reaction? ____ increase ___________ (d) equilibrium constant of the reaction? ____ no change _________ (12) 2. An enzyme catalyzes a reaction at a velocity of 20 μ mol/min when the concentration of substrate [S] is 0.01 M. The K m for this substrate is 1 × 10 –5 M. Assuming that Michaelis- Menten kinetics are followed, what will the reaction velocity be when the concentration of S is (a) 1 × 10 –5 M and (b) 1 × 10 –6 M? (Hint: you can make a simplifying assumption.) The velocity of 20 μ mol/min is essentially V max , because it is measured at [S] >> K m . (a) When [S] = 10 –5 M = K m , V = 1/2 V max , or 10 μ mol/min. (b) When [S] is 10 –6 M, velocity can be calculated from the Michaelis-Menten equation: V = V max [S]/( K m + [S]) = (20 μ mol/min)(10 –6 M)/(10 –5 + 10 –6 ) = 1.8 μ mol/min. 3. A hemoglobin purified from sea cucumber shows some unusual properties. For one thing, it has 8 subunits, rather than the usual 4. A plot of log ( θ / 1- θ29 versus log pO2 is shown below: (3) (a) What is the theoretical maximum number for the Hill coefficient? ______________ 8 (3) (b) What is the actual Hill coefficient? ___________4 (4) (c) What is the P 50 of this molecule (ignore units)? ___________log P50 = 1.75, so P50 = 10 1.75 = 56 2...
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## This note was uploaded on 11/30/2009 for the course CH 55655 taught by Professor Marcotte during the Spring '09 term at University of Texas.

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ExamIII_Fall2007_key - 1 Fall 2007 EXAM III Name Dr...

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