Mitchell, Peter Dennis (1920–1992)

English chemist. He was awarded the Nobel Prize for Chemistry in 1978 for work on the conservation of energy by plants during respiration and photosynthesis. He showed that the transfer of energy during life processes is not random but directed.

Mitchell was born in Mitcham, Surrey, and studied at Cambridge. He worked at the Chemical Biology Unit in the Department of Zoology at Edinburgh 1955–63, and then established the privately run Glynn Research Institute at Bodmin, Cornwall.

It had been believed that the energy absorbed by animals from food and by plants from sunlight was utilized in cells by purely chemical means. The cell was seen as a bag of enzymes in which random and directionless processes took place. Mitchell proved that currents of protons pass through cell walls, which, instead of being simple partitions between cells, are, in fact, full of directional pathways. This discovery demonstrated the existence of a reverse kind of electricity (Mitchell called it ‘proticity’), which he successfully used to run an engine.