Chemiosmotic theory postulated by the British biochemist, Peter Mitchell (1920-22) to explain the formation of ATP in the mitochondrial electron transport chain. As
electrons are transferred along the electron carrier system in the inner mitochondrial membrane, hydrogen ions (protons) are actively transported into the space between the inner and outer mitochondrial membranes, which thus contains a higher concentration of protons than the matrix. This creates an electrochemical gradient across the inner membrane, through which protons move back into the matrix.