SECTION 4: ETS & OXIDATIVE PHOSPHORYLATION

Electron Transport System (ETS) – Location

Inner mitochondrial membrane

How does the ETS work?

NADH and FADH₂ donate electrons to protein complexes. Electrons pass down the chain releasing energy. Final electron acceptor is O₂ → forms H₂O.

Chemiosmosis & ATP Synthase

H⁺ pumped into intermembrane space by ETS. Proton gradient builds. H⁺ flows back through F₀F₁-ATP synthase, driving synthesis of ATP from ADP + Pᵢ.

Why must oxidative phosphorylation occur?

Without O₂ as the final electron acceptor, the ETS halts, NADH/FADH₂ cannot be re-oxidized, and aerobic respiration cannot continue.

Brown Fat & Heat Production

Brown fat has uncoupling proteins that allow H⁺ to bypass ATP synthase and flow back across the membrane as heat instead of ATP. Important in newborns for thermogenesis. Reduces ATP synthesis.

Total ATP per Glucose (complete oxidation)

~32 ATP net. Glycolysis: 2 ATP + 2 NADH. Pyruvate→Acetyl CoA: 2 NADH. Krebs: 2 ATP + 6 NADH + 2 FADH₂. ETS converts NADH/FADH₂ into the remaining ATP.