In chemiosmosis, what is the most direct source of energy that is used to convert adp + ℗i to atp?

In the electron transport chain, there are multiple reduction-oxidation reactions that generate a proton gradient between the inner membrane space and the mitrocondrial matrix. The most direct source of energy is the last complex of the electron transport chain wherein the proton gradient goes to the complex called the ATP synthase and produce ATP from ADP and inorganic phosphate.

Orbit is represented by the blank space