A process of biological oxidation in which electrons are transferred from a reduced substrate through a series of compounds to oxygen, the energy of the process being conserved by the formation of high-energy bonds in the form of adenosine triphosphate (an organic compound composed of adenine or base, the sugar ribose, and three phosphate groups) which serves as the major energy source within a cell to drive a number of biological processes; such as, photosynthesis, muscle contraction, and the synthesis of proteins.

1. A series of electron carriers which occurs within certain membranes; such as, the mitochondrial membrane, and produces energy for a cell.
2. The final common pathway of biological oxidation, the series of electron carriers in the inner mitochondrial membrane which pass electrons from reduced co-enzymes to molecular oxygen via sequential redox (oxidation-reduction) reactions coupled to proton transport, generating energy for biological processes.

The conversion of inorganic phosphate into pyrophosphate from a reaction powered by energy in a transmembrane gradient of ions generated by an electron transport chain.

It occurs in respiratory metabolism and in some types of fermentation.

1. A series of reduction-oxidation reactions, beginning with increased strength and ending in oxygen, which constitutes the final stage of aerobic respiration.

It is also involved in the light reaction of photosynthesis.

2. The components of the final sequence of reactions in biological oxidations.

They are composed of a series of oxidizing agents arranged in an order of increasing strength and terminating in oxygen.