. . "|FRAME: NAD NAD⁺| and |FRAME: NADP NADP⁺| are two forms of |FRAME: NIACINE nicotinate|. These molecules are the biological carriers of reductive equivalents (i.e. high potential electrons). They are often referred to as coenzymes, although in most of their reactions they function as cosubstrates rather than true coenzymes. The most common function of NAD+ is to accept two electrons and a proton (a hydride ion) from a substrate that is being oxidized. This reduction converts NAD+ to |FRAME: NADH NADH|, the reduced form. NADH then diffuses or is being transported to a terminal oxidase, where the electrons are passed on, regenerating the oxidized form. |FRAME: NADPH NADPH|, on the other hand, is mostly involved in biosynthetic reactions, where it serves as an electron donor. NADPH is formed by reduction of NADP+, which occurs by different mechanisms in different types of organisms. In photosynthetic organisms NADP+ is reduced by |FRAME: CPLX-84 photosystem I|. In heterotrophic organisms NADP+ is reduced by central metabolism processes such as the pentose phosphate pathway (see |FRAME: OXIDATIVEPENT-PWY pentose phosphate pathway (oxidative branch)|)."^^ . . . "NADH"^^ . "NADH₂"^^ . "nicotinamide adenine dinucleotide reduced"^^ . "NADH2"^^ . "diphosphopyridine nucleotide reduced"^^ . "NAD-reduced"^^ . "dihydronicotinamide adenine dinucleotide"^^ . "NADH+H+"^^ . "DPNH"^^ . "dihydrodiphosphopyridine nucleotide"^^ . . "NADH"^^ .