FAD

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For other uses, see FAD (disambiguation).

In biochemistry, flavin adenine dinucleotide (FAD) is the precursor molecule to FADH₂. Upon bonding to two hydrogen atoms, FAD is reduced to FADH₂ and is turned into an energy-carrying molecule. FAD accommodates two equivalents of Hydrogen; both the hydride and the proton ions. This is used by organisms to carry out energy requiring processes. FAD, and the more common NAD, are reduced in the citric acid cycle during aerobic respiration.

FAD is a coenzyme derived from riboflavin, or vitamin B₂. Many oxidoreductases, called flavoenzymes or flavoproteins, require FAD as a prosthetic group which functions in electron transfers. FADH₂ may donate electrons either one or two at a time.