Explain photophosphorylation in terms of chemiosmosis

As the electrons cycle through the electron transport chains located on the thylakoid membrane, they lose energy
This free energy is used to pump H+ ions from the stroma into the thylakoid
The build up of protons inside the thylakoid creates an electrochemical gradient
The H+ ions return to the stroma via the transmembrane enzyme ATP synthase, which uses the potential energy from the proton motive force to convert ADP and an inorganic phosphate (Pi) into ATP