the force that promotes the movement of protons across membranes ![[Pasted image 20250327161529.png]] A difference of solute concentration between two compartments separated by a biological membrane generates a tendency to equilibrium, which, in the case of protons, is called proton motive force (PMF). This is measured in terms of the potential energy resulting from the difference in concentration between the two compartments. With a charged solute, the potential has two components: the chemical (concentration) and the electrical potentials, thus, it is named electrochemical potential.