| Section2 = | Section3 = }} In biochemistry, flavin adenine dinucleotide (FAD) is a redox cofactor involved in several important reactions in metabolism. FAD can exist in two different redox states and its biochemical role usually involves changing between these two states. FAD can be reduced to the FADH2, whereby it accepts two hydrogen atoms: » FADH2 is an energy-carrying molecule, and the reduced coenzyme can be used as a substrate for oxidative phosphorylation in the mitochondria. FADH2 i… (More on Fad)