Here's why:
* NAD+ is the oxidized form of the molecule. It has a positive charge and is ready to accept electrons.
* NADH is the reduced form. It gains a hydrogen atom, which consists of a proton (H+) and an electron (e-). The electron is added to the nicotinamide ring of NAD+, reducing it.
This reduction reaction is a key step in many metabolic processes, particularly in cellular respiration, where NADH carries electrons to the electron transport chain, ultimately leading to ATP production.
