Final answer:
NAD+ is reduced to form NADH by accepting two hydrogen ions and two electrons, becoming a key energy carrier in cellular respiration.
Step-by-step explanation:
Nicotinamide adenine dinucleotide (NAD) is reduced to form NADH. NAD+ is the oxidized form of NAD and is composed of two nucleotides, one being adenosine diphosphate (ADP) and the other with nicotinamide, a nitrogen base derived from vitamin B3 or niacin. The process of reduction involves the molecule accepting two electrons and a hydrogen ion (proton), which effectively adds one more hydrogen ion and two electrons to the structure compared to its oxidized state.The general equation for NAD+ reduction can be written as: NAD+ + 2H+ + 2e‑ → NADH + H+. Here, NAD+ gains electrons (e‑) and a hydrogen ion, resulting in its conversion to NADH. This reaction is essential for various biochemical processes, including those in cellular respiration where NADH is used to generate ATP, the energy currency of the cell.In conclusion, the biochemical transformation of NAD+ to NADH is a key step in the metabolic pathways that energize living cells.