(a) Consider the malate dehydrogenase reaction, which is part of the citric acid cycle: malate + NAD+ → oxaloacetate + NADH + H* In yeast mitochondria, where the pH = 8.1, this reaction is exergonic only at low oxaloacetate concentrations. Assuming a pH = 8.1, a tem- perature of 37 °C, and the steady-state concentrations given below, cal- culate the maximum concentration of oxaloacetate at which the reaction will still be exergonic. malate = 410 µM pyruvate = 3.22 mM lactate = 1.10 mM NAD+ = 20.0 mM ΝADH -290 μΜ CO, = 15.5 torr E°' (V) half reaction Pyruvate + CO, + H* + 2e Pyruvate + 2H+ + 2e malate -0.330 lactate -0.190 oxaloacetate + H* - pyruvate + CO2 AG" = -30.9 kJ/mol lactate + NAD* pyruvate + NADH + H* AG" = +25.1 kJ/mol (b) How would a drop in pH affect AG for the reaction described in part (a)? (c) How would an increase in intracellular malate levels affect AG for the reaction in part (a)? (d) How would an increase in intracellular pyruvate levels affect AG for the reaction in part (a)?

(a) Consider the malate dehydrogenase reaction, which is part of the citric acid cycle: malate + NAD+ → oxaloacetate + NADH + H* In yeast mitochondria, where the pH = 8.1, this reaction is exergonic only at low oxaloacetate concentrations. Assuming a pH = 8.1, a tem- perature of 37 °C, and the steady-state concentrations given below, cal- culate the maximum concentration of oxaloacetate at which the reaction will still be exergonic. malate = 410 µM pyruvate = 3.22 mM lactate = 1.10 mM NAD+ = 20.0 mM ΝADH -290 μΜ CO, = 15.5 torr E°' (V) half reaction Pyruvate + CO, + H* + 2e Pyruvate + 2H+ + 2e malate -0.330 lactate -0.190 oxaloacetate + H* - pyruvate + CO2 AG" = -30.9 kJ/mol lactate + NAD* pyruvate + NADH + H* AG" = +25.1 kJ/mol (b) How would a drop in pH affect AG for the reaction described in part (a)? (c) How would an increase in intracellular malate levels affect AG for the reaction in part (a)? (d) How would an increase in intracellular pyruvate levels affect AG for the reaction in part (a)?

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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