GSSG + NADPH + H+ 2GSH + NADP+ (a) Calculate G for the glutathione reductase reaction

Question:

GSSG + NADPH + H+ †’ 2GSH + NADP+
(a) Calculate ˆ†G°€² for the glutathione reductase reaction in the direction shown, using E°€² values from Table 14.1.
(b) Suppose that a cell contained an isoform of glutathione reductase that used NADH instead of NADPH as the reductive coenzyme. Would you expect ˆ†G°€² for this enzyme to be higher, lower, or the same as the corresponding value for the real glutathione reductase? Briefly explain your answer.
(c) Given what you know about the metabolic roles and/or intracellular concentration ratios of NAD+ /NADH and NADP+ /NADPH, would you expect ˆ†G (not ˆ†G°€²) for this enzyme to be higher, lower, or the same as ˆ†G for the real enzyme under intracellular conditions? Briefly explain your answer.