How ATP Synthase Really Makes ATP

Lesson notes

Key points

• The electron transport chain uses energy from NADH and FADH₂ to pump protons into the intermembrane space.
• This creates the proton-motive force, a combined gradient of proton concentration and electrical charge across the inner membrane.
• Protons flow back through ATP synthase, spinning its rotor and driving conformational changes that join ADP and phosphate.
• Uncouplers let protons leak across the membrane, so energy escapes as heat instead of ATP, as in brown fat.

Definitions

Proton-motive force

Stored energy from the H⁺ concentration gradient (ΔpH) plus membrane potential (Δψ) across a membrane

Takeaway: Electron transport builds a proton gradient; ATP synthase spends it.

Proton pumpingProton-motive forceATP synthaseUncoupling