The proton motive force is the force generated by the movement and difference of the charge inside and outside the membrane. The proton motive force is generated due to the electron transport chain as the flow of electron causes the movement of hydrogen ions from the matrix to the inter-membrane space.
This leads to the increase of H⁺ ion concentration in inter-membrane space and lowering of the H⁺ ions in the matrix. This difference in the charges causes the generation of force called proton motive force which helps the synthesis of ATP.
