AP BIOLOGY

Detailed explanation-1: -During the link reaction, a carbon atom is removed from pyruvate, forming carbon dioxide. This converts pyruvate into a two-carbon molecule called acetate. Hydrogen is also removed from pyruvate in the conversion into acetate, which is picked up by the coenzyme NAD to form reduced NAD.

Detailed explanation-2: -A carboxyl group is removed from pyruvate and released as carbon dioxide. The two-carbon molecule from the first step is oxidized, and NAD+ accepts the electrons to form NADH. The oxidized two-carbon molecule, an acetyl group, is attached to Coenzyme A to form acetyl CoA.

Detailed explanation-3: -NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the Krebs cycle. NAD+ has more chemical energy than NADH. NAD+ donates high energy electrons to the electron transport chain. In the absence of NAD+, glycolysis can still function.