Mitchell, Peter Dennis (1920-1992), was a British chemist who proposed a theory of how energy is transported and stored in the living cell. It took him many years of research in his own private research institute to get the evidence that convinced other chemists and earned him the Nobel Prize for chemistry in 1978.
Mitchell was born in Mitcham, Surrey, England. He obtained his Ph.D. at Cambridge University in 1950 for his work on penicillin. In 1955, he set up and directed the Chemical Biology Unit at Edinburgh University, until ill health forced him to resign in 1963. Mitchell then set up his own institute, the Glynn Research Institute, in Cornwall, England, to undertake a program of biochemical research. He directed the institute until 1986. Mitchell was interested in how plant cell structures called mitochondria store energy (see Cell (The cytoplasm) ). The energy originally comes from sunlight and is stored in a substance called adenosine triphosphate (ATP). Energy is released when a group of phosphorus and oxygen atoms splits off from the ATP, leaving a molecule of adenosine diphosphate (ADP) or adenosine monophosphate (AMP). The released energy produces chemical reactions in the organism, such as those involved in muscle contraction or in the production of chemical substances. Energy reserves in the cell are then refilled by regenerating (renewing) the ATP molecule. The plant does this by using energy from sunlight to rejoin one or more phosphorus group or groups to the ADP and AMP molecules.
This process was only partly understood. Mitchell contributed to a much clearer understanding of it. His explanation involved the movement of positive hydrogen ions (protons). By a process called chemiosmosis, protons are transported through the outer membrane of the mitochondria and accumulate outside them. This process creates an electric potential (voltage) that powers the energy storage process.
