Question

Use the table below as the basis for the calculations needed to answer the following questions, Standard Reduction Potentials for Redox Pairs of Biological Relevance Redox Pair (oxidized form Number of Standard Reduction reduced form) electrons Potential, Volts Acetate → pyruvate 2 -0.70 Succinate-ketoglutarate 2 -0.67 Acetate acetaldehyde 2 -0.60 3-phosphoglycerate → 2 -0.55 glyceraldehyde-3-P a-ketoglutarate isocitrate 2 -0.38 2 -0.32 2 -0.30 N -0.29 NAD+ NADH FMNFMNH2 1,3-bisphosphoglycerate → glyceraldehyde-3-P Acetaldehyde ethanol Pyruvate lactate FAD FADH2 Oxaloacetatemalate 2 -0.20 2 -0.19 2 -0.18 2 -0.17 Fumarate succinate 2 -0.03 2 0.00 2 +0.04 2H+ + H2 CoQ COQH2 Fe3+ + Fe2+ (inorganic ion) 02 + H20 1 +0.77 2 +0.816 Each Standard Reduction Potential is for the following half-reaction, where n is the number of electrons transferred: oxidized + nH+ + ne → reduced form.

Answer 1

Chemical equation for reduction of lactate to pyruvate by NAD+

Lactate + NAD+ --> Pyruvate + NADH + H+

Half-reactions of the above reaction:

Pyruvate + 2H+ + 2e- => lactate ; ∆E°' = -0.19V

NAD+ + H+ + 2e- => NADH ; ∆E°' = -0.32V

Now,

∆E°' = -0.32 V - ( - 0.19 V) = -0.13 V

As we know, ∆G°' = -nF∆E°'

=> ∆G°' = -2 X 23.06 kcal/mol X (-0.13V)

=> ∆G°' = 5.9956 kcal/mol = 6 kcal/mol (approximately)

Thus, the required answer is ∆G°' = 6 kcal/mol.