BIBC HW 2 Sol

BIBC HW 2 Sol - KEY Metabolic Biochemistry Summer 2010...

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Metabolic Biochemistry KEY Summer 2010 Homework 2 (40 pts.) 1) (8 pts.) The following data was collected from kinetic analysis performed on new enzyme: [S] ( mol/L) 1/[S] V 0 (( mol/L)min -1 ) 1/V 0 5 0.2 22 0.045 10 0.1 39 0.026 20 0.05 65 0.015 50 0.02 102 0.010 100 0.01 120 0.008 200 0.005 135 0.007 a. On graph paper, prepare a Lineweaver-Burke plot from the data and estimate V max and K M. 1/[S] 1/V max : Vmax = approx. 162 ( mol/L)min -1 -1/K M : K M = approx. 32 mol/L 1/V 0 b. If the total enzyme concentration is 1 nmol/L, and enough substrate has been added to achieve the maximum velocity for the reaction (V max ), how many molecules of substrate are converted to product by one molecule of enzyme in one second? (Show your work.) V max = k cat [E t ] turnover number = k cat = V max /[E t ] 162 x10 -6 M/min = 1.62 x10 5 molecules/ min. = 2700 molecules/ sec. 1 x10 -9 M
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2) (8 pts.) Sketch a Michaelis_Menten plot (V 0 vs. [S]—not a reciprocal plot) for an enzyme with and without an irreversible inhibitor. You can assume that the enzyme molecule is destroyed when it reacts with the inhibitor. Clearly label V max and K M with and without the inhibitor. V max Enzyme alone V 0 [S] V max ½ V max enzyme alone ½ V max enzyme + inhib. Enzyme + inhib. K M 3) (8 pts.) In glycolysis, glucose-6-phosphate is converted to fructose-6-phosphate. If the reactants and products have the following concentrations at equilibrium , calculate the standard free energy change ( G’°) for the reaction at 25°C. glucose-6-phosphate fructose-6-phosphate (9.6x10 -2 M) (4.8x10 -2 M) First calculate K’ eq ; K’ eq = [product] eq /[reactant] eq = .048 M/.096 M = 0.5 G’° can be calculated from K’ eq using the formula G’° = -RT ln K’ eq G’° = -(8.315 J/mol•K)(298 K)( ln 0.5) = -(2477.9 J/mol)(-0.693) = 1717.2 J/mol = 1.72 kJ/mol
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This note was uploaded on 09/20/2011 for the course BIBC 102 taught by Professor Price during the Summer '02 term at UCSD.

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BIBC HW 2 Sol - KEY Metabolic Biochemistry Summer 2010...

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