Malate dehydrogenase mechanism.

The oxidation-reduction progression involving alcohols, aldehydes/ketones, carboxyl groups, and carbon dioxide is important both for biosynthesis and energy metabolism. Here are a few more examples which are good to contemplate for the MCAT.

The conversion of pyruvate to lactate involves reduction of a carbonyl group to a hydroxyl group.

The hydroxyl group of malate is oxidized to a carbonyl in oxaloacetate by malate dehydrogenase.

The corticosteroids cortisol and cortisone differ from each other by the reduction of a single carbonyl group.