Question

What are NAD+, NADH, and NADPH?

Answer 1

NAD + (nicotinamide adenine dinucleotide) is an electron carrier molecule. NADH shows the hydrogen ion. NADPH is similar but it has a phosphate group.

Explanation:

NAD
Used as a coenzyme to transfer energy-carrying molecules from one chemical pathway to another,

Energized electrons are carried by NADH and FADH2 from glycolysis and the citric acid cycle to electron acceptors embedded in the cristae of the mitochondrion.

As electrons are shuttled along a chain of electron-accepting molecules in the cristae, their energy is used to pump accompanying protons (H+) into the space between mitochondrial membranes.

The extra phosphate group on NADPH is far from the region involved in electron transfer and is of no importance to the transfer reaction. It does, however, give a molecule of NADPH a slightly different shape from that of NADH, and so NADPH and NADH bind as substrates to different sets of enzymes. The two types of carriers are used to transfer electrons (or hydride ions) between different sets of molecules.

You'll find some more information about this in chapter 2 of "Molecular Biology of the Cell" by Alberts et al.