Chemiosmosis is the process by which chemical ions move from an area of high concentration to an area of low concentration across a selectively permeable membrane. Chemiosmosis is the process by which ATP, or adenosine triphosphate, is synthesized.
During this movement, hydrogen ions diffuse across a biological membrane using a transport protein, specifically ATP synthase. These protons begin travel because of a gradient that forms on the other side of the membrane. The accumulation of hydrogen ions in the area of higher concentration and the forced movement of ions across the membrane via carrier proteins triggers the formation of the electrochemical concentration gradient. While protons move to the other side of the membrane, electrons flow through the electron transport chain. This reoccurring flow of protons and electrons releases energy. This energy is used to convert ADP, or adenosine diphosphate, to ATP. This conversion is completed by a process called phosphorylation. Phosphorylation is simply the addition of a phosphate group to an organic molecule. Chemiosmosis generally occurs in chloroplasts, mitochondria, bacteria and archaea. The generation of ATP regularly occurs during cellular respiration. The chemiosmotic hypothesis was proposed by Peter D. Mitchell in 1961. In 1978 the chemist was awarded the Nobel Prize in Chemistry.