Question

The half-reactions involved in the lactate dehydrogenase (ldh) reaction and their standard reduction potentials are

Answer 1

Enzyme lactate dehydrogenase catalyses the conversion of lactate to pyruvate. In this reaction lactate loses two electrons (becomes oxidized) and is converted to pyruvate. NAD+ gains two electrons (is reduced) and is converted to NADH. The half reactions involved are;

NAD+ + H+ + 2e- = NADH    -0.320
Pyruvate + 2H+ + 2e- = Lactate   -0.185
Giving an overall reaction of; 
Lactate + NAD+ = Pyruvate + NADH + H+