Peter Mitchell was an English chemist, was the 1978 Nobel Laureate in Chemistry for his contribution to the understanding of biological energy transfer through the formulation of the chemiosmotic theory. According to the chemiosmotic model, the stepwise transfer of electrons through electron carriers to oxygen results in the release of energy. This energy is used to pump protons across the inner mitochondrial membrane into the space between the inner and outer mitochondrial membranes.

In the 1960s, ATP was known to be the energy currency of life, but the mechanism by which ATP was created in the mitochondria was assumed to be by substrate-level phosphorylation. Mitchell's chemiosmotic hypothesis was the basis for understanding the actual process of oxidative phosphorylation. At the time, the biochemical mechanism of ATP synthesis by oxidative phosphorylation was unknown.

Mitchell realized that the movement of ions across an electrochemical membrane potential could provide the energy needed to produce ATP. His hypothesis was derived from information that was well known in the 1960s. He knew that living cells had a membrane potential; interior negative to the environment. The movement of charged ions across a membrane is thus affected by the electrical forces (the attraction of plus to minus charges). Their movement is also affected by thermodynamic forces, the tendency of substances to diffuse from regions of higher concentration. He went on to prove that ATP synthesis was coupled to this electrochemical gradient.

His theory was confirmed by the discovery of ATP synthase, a membrane-bound protein that uses the potential energy of the electrochemical gradient to make ATP.

Sources

• Cleveland, Cutler (Lead Author); Peter Saundry (Topic Editor). 2007. "Mitchell, Peter." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [Published in the Encyclopedia of Earth March 19, 2007; Retrieved July 26, 2009]. 
• Wikipedia Contributors, Peter D. Mitchell, Wikipedia The Free Encyclopedia, Accessed 26 July 2009.