Chapter 3, Problem 18P

Consider the degradation of glucose to pyruvate by the glycolytic pathway:

Glucose + 2ADP + 2P_i + 2NAD+ $\to$ 2pyruvate + 2ATP + 2H₂O + 2NADH + 2H+
Calculate $\Delta$ G for this reaction at pH = 7.4 and 37^o C when reactants and products are at concentrations given in Problem 17.

17. For part (b) of this problem, use the following reduction potentials, free energies, and nonequilibrium concentrations of reactants and products:

Consider the last two steps in the alcoholic fermentation of glucose by brewer's yeast:

Pyruvate + NADH + 2H+ $\to$ ethanol + NAD+ + CO₂

a. Do you predict that $\Delta$ S for this reaction is > O or < O?
b. Calculate the nonequilibrium concentration of ethanol in yeast cells, if $\Delta$ G = -38.3 kJ /mol for this reaction at
pH = 7.4 and 37^o C when the reactants and products are at the concentrations given above.
c. How would a drop in pH affect $\Delta$ G for the reaction described in pan (b)?
d. How would an increase in intracellular CO₂ levels affect $\Delta$ G for the reaction in part (b)?
e. How would an increase in intracellular CO₂ levels affect $\Delta$ G^o' for the reaction in part (b)?