<P> An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane . The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and the electrical gradient, or difference in charge across a membrane . When there are unequal concentrations of an ion across a permeable membrane, the ion will move across the membrane from the area of higher concentration to the area of lower concentration through simple diffusion . Ions also carry an electric charge that forms an electric potential across a membrane . If there is an unequal distribution of charges across the membrane, then the difference in electric potential generates a force that drives ion diffusion until the charges are balanced on both sides of the membrane . </P> <P> Electrochemical potential is important in electroanalytical chemistry and industrial applications such as batteries and fuel cells . It represents one of the many interchangeable forms of potential energy through which energy may be conserved . </P> <P> In biological processes, the direction an ion moves by diffusion or active transport across a membrane is determined by the electrochemical gradient . In mitochondria and chloroplasts, proton gradients are used to generate a chemiosmotic potential that is also known as a proton motive force . This potential energy is used for the synthesis of ATP by oxidative phosphorylation or photophosphorylation, respectively . </P> <P> An electrochemical gradient has two components . First, the electrical component is caused by a charge difference across the lipid membrane . Second, a chemical component is caused by a differential concentration of ions across the membrane . The combination of these two factors determines the thermodynamically favourable direction for an ion's movement across a membrane . </P>

What uses the energy found within a proton gradient to drive the synthesis of atp