Topic overview

Start with the big picture

Electron flow is energetically favorable from carriers with more negative standard reduction potentials to those with more positive potentials. Its free-energy change is related to the potential difference by ΔG°′ = –nFΔE°′, while the Nernst equation helps describe actual potentials under cellular conditions. In electron transport chains, sequential carriers enable stepwise energy conversion. Exergonic transfer can power proton pumps, building the proton-motive force from membrane potential (Δψ) and a pH gradient (ΔpH). ATP synthesis uses this stored electrochemical energy. The lesson also distinguishes proton-pumping complexes from electron-transfer routes that do not pump, and introduces specialized coupling mechanisms, photosynthetic electron flow, and the consequences of electron leakage.