Proton-motive force is generated by actively pumping protons across a biological membrane, creating a concentration gradient. This process occurs in the inner mitochondrial membrane during cellular respiration. 

The generation of the proton-motive force starts when high-energy electrons move through the electron transport chain in the inner mitochondrial membrane, creating a flow of protons across the membrane. As electrons move through the protein complexes in the electron transport chain, protons are actively pumped across the membrane from one side to the other. The proton concentration gradient created by the pumping creates potential energy is also known as the proton-motive force.