In a respiring mitochondrion, what immediately powers ATP synthase as it manufactures ATP?

Core Concept

Electron transport complexes use energy from nutrient oxidation to pump protons from the matrix into the intermembrane space. The stored electrochemical gradient, called the proton-motive force, represents potential energy awaiting release. When protons diffuse back through ATP synthase channels, that flow turns the enzyme's rotor and drives phosphorylation of ADP. Remove the gradient and the enzyme stalls even with abundant fuel.