In the reaction where glyceraldehyde-3-phosphate + NAD+ yields 1,3-biphosphoglycerate + NADH, what happens to NAD+?

In the reaction where glyceraldehyde-3-phosphate combines with NAD+ to produce 1,3-biphosphoglycerate and NADH, NAD+ acts as an electron acceptor. During this process, NAD+ undergoes a reduction, which means it gains electrons and is converted into NADH.

In biochemical terms, reduction refers to the gain of electrons or hydrogen ions, while oxidation refers to the loss of electrons or hydrogen. Here, the glyceraldehyde-3-phosphate is oxidized; as it loses electrons, these electrons are captured by NAD+, resulting in the formation of NADH. Thus, the reduction of NAD+ is a key aspect of this reaction, as it allows the transfer of energy within the cell and the regeneration of NADH, which can be utilized in various metabolic pathways, including cellular respiration.

Consequently, the correct answer is that NAD+ is reduced in this reaction, as it is transformed from an oxidized state to a reduced state (NADH). This highlights the important role NAD+ plays in facilitating cellular energy metabolism and the interconnectedness of oxidation-reduction reactions in biochemistry.