Answer: Nicotinamide Adenine Dinucleotide (NAD+) is reduced to NADH.
This oxidation-reduction takes place in the Step 6, of glycolysis pathway; when Phosphorylates Glyceraldehyde-3-Phospahte(GAP) was oxidized by NAD+( thus reduced to NADH) and phosphorylated by enzyme Glyceraldehyde-3-phophate dehydrogenase (GAPDH) to form 1-3- bisphosphoglycerate(an intermediate in pyruvate formation).
The mechanism involves oxidation of GAP(removal of hydrogen (dehydrogenation) and the pick up of the released hydrogen atom by co- enzyme NAD+( the oxidizing agent) which undergoes reduction to form NADH.
The next reaction is phosphorylation (addition of phosphate atom ) of the oxidized GAP so that it is released by enzyme GAPH to from 1-3- bisphosphoglycerate, NADH, and H .
Step-by-step explanation: