How do protons move back across the membrane out of the thylakoid lumen?

Step-by-step solution

The proton gradient is broken down due to the movement of protons across the membrane to the stroma through the transmembrane channel of the CF0 of the ATP synthase. The ATP synthase enzyme consists of two parts: one called the CF0 is embedded in the thylakoid membrane and forms a transmembrane channel that carries out facilitated diffusion of protons across the membrane. The other portion is called CF1 and protrudes on the outer surface of the thylakoid membrane on the side that faces the stroma. The break down of