Max Animations

Energy-rich molecules, such as glucose or fatty acids, are metabolized by series of oxidation reactions ultimately yielding Co2 and water. The metabolic intermediates of these reactions donate electrons to specialized coenzymes, nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD), to form the energy-rich reduced conenzymes, NADH and FADH2. These reduced coenzymes can, in turn, each donate a pair of electrons to a specialized set of electron carriers,  collectively called the electron transport chain.

As electrons are passed down the electron transport chain, they lose much of their free energy. Port of this energy can be captured and stored by the reduction of ATP from ADP and inorganic phosphate (P). This process is called oxidative phosphorylation.