kemiosmoositeorians

Chemiosmosis is a biological mechanism by which energy, released by a proton gradient, is used to synthesize ATP. This process is central to cellular respiration and photosynthesis. In eukaryotes, chemiosmosis occurs across the inner mitochondrial membrane during cellular respiration and across the thylakoid membrane in chloroplasts during photosynthesis. In prokaryotes, it takes place across the plasma membrane.

The theory, often referred to as the chemiosmotic theory, was first proposed by Peter Mitchell in 1961. He hypothesized that the electron transport chain, embedded in a membrane, pumps protons across the membrane, creating an electrochemical gradient. This gradient represents stored potential energy, analogous to water behind a dam. The flow of protons back across the membrane through a specific enzyme, ATP synthase, drives the phosphorylation of ADP to ATP.

ATP synthase acts as a molecular motor. The energy from the proton motive force is harnessed by the rotation of subunits within ATP synthase, facilitating the chemical reaction that joins a phosphate group to ADP, forming ATP. This energy currency of the cell is then utilized for various cellular processes. The chemiosmotic theory revolutionized our understanding of energy metabolism in living organisms.