In 1961, chemiosmotic theory was proposed by Peter D. Mitchell, a British biochemist, that suggested an electrochemical link between phosphorylation and cellular respiration. Later, in 1978, he was awarded a Nobel prize for chemistry for his work on the mechanism of synthesis of ATP across the inner mitochondrial membrane in cells.
The process of chemical ions moving across a semi-permeable membrane according to their electrochemical or proton gradient from a zone of higher to lower concentration is known as chemiosmosis. This process is comparable to the osmosis process of water molecules. A good illustration is the process by which hydrogen ions pass through a membrane to produce ATP during cellular respiration or photosynthesis that occur in specialized cell organelles such as chloroplasts and mitochondria.
During the electron transport chain (ETC) process, which produces ATP. Protons generate a gradient that occurs, particularly in the inner membrane of the mitochondria, and this gradient is the main factor in the creation of ATP molecules. This occurs as a result of molecules with high energy content, such glucose, breaking down. The enzyme known as ATP Synthase complex is responsible for moving the protons across the inner membrane.
The proton gradient which is generated by the efflux of hydrogen ions from the mitochondrial matrix to the mitochondrial intermembrane space (IMS). Eventually, proton motive force (PMF) allows the hydrogen ion from the IMS to the mitochondrial matrix from the ATP synthase complex that leads to the generation of ATP through oxidative phosphorylation.