(proton-motive force - physical gradient, no enzyme)

Formation of proton-motive force: electrochemical H+ gradient across the inner membrane — The inner membrane is normally nearly impermeable to protons, allowing a membrane potential (Delta psi, matrix negative) and a pH gradient (Delta pH, matrix more alkaline) to develop. The proton-motive force is commonly expressed as \Delta p = \Delta \psi - (2.303RT/F)\Delta pH; in respiring mitochondria it is often on the order of 150–200 mV, with the electrical component usually dominant. No discrete enzyme catalyzes this state; it depends on the respiratory chain, membrane integrity, and controlled proton return.