chemiosmosis: a standalone construct

Peter Mitchell proposed chemiosmosis in 1961 (Nature), arguing that the energy cells extract from food or light is stored not as a chemical intermediate but as a proton gradient, a difference in hydrogen-ion concentration and electrical charge held across a membrane. In his 1966 monograph he set out the full chemiosmotic theory: enzymes embedded in the membrane pump protons to one side, and the protons then flow back down this gradient through the enzyme ATP synthase, whose movement drives the synthesis of ATP, the cell's main energy currency. The stored energy of the gradient, called the proton-motive force, couples two processes that had long been studied separately, electron transport and phosphorylation, without any high-energy chemical intermediate linking them. Mitchell received the 1978 Nobel Prize in Chemistry for the theory, and the 1966 acid-bath experiment of Jagendorf and Uribe, in which an imposed pH jump alone made chloroplasts produce ATP, showed that a gradient by itself can drive synthesis. What makes chemiosmosis a landmark is its reach: it explains how the mitochondria of animals, the chloroplasts of plants, and the membranes of bacteria all conserve energy by the same mechanism.[1][2][3]

Unit

The proton-motive force stored across a membrane, an electrochemical potential difference for protons expressed in millivolts

Recovery means

Not applicable

Measured by

Quantified from the transmembrane pH difference and electrical potential (for example with pH-sensitive and voltage-sensitive probes) together with rates of ATP synthesis under measured or imposed gradients