Explain oxidative phosphorylation with the chemiosmotic theory. Add a note on inhibitors and uncouplers.

1. 1 · Open in two lines. Oxidative phosphorylation is the making of ATP from ADP and Pi, using energy released as electrons flow through the ETC to oxygen. It takes place in the inner mitochondrial membrane.
2. 2 · Draw the chemiosmotic model. [Diagram: inner membrane with Complexes I, III, IV pumping H+ out; H+ returning through F0F1 ATP synthase; ADP + Pi → ATP in the matrix]
3. 3 · Explain the chemiosmotic theory.
   • Complexes I, III and IV pump H+ into the intermembrane space.
   • A proton gradient (proton-motive force) builds up.
   • The inner membrane does not let H+ leak back.
   • H+ returns through F0; F1 makes ATP.
4. 4 · ATP synthase and P/O ratio. F0 is the proton channel; F1 is the catalytic head. P/O: NADH 3 (older) or 2.5 (newer); FADH2 2 or 1.5.
5. 5 · Inhibitors and uncouplers.
   • Complex I: rotenone, amytal. Complex III: antimycin A. Complex IV: cyanide, CO.
   • ATP synthase: oligomycin.
   • Uncouplers: 2,4-DNP, thermogenin (brown fat).
6. 6 · Significance. Makes most of the ATP in aerobic cells. Controlled uncoupling in brown fat produces body heat.
7. 7 · Nutrition link. Magnesium for ATP; niacin and riboflavin for NADH and FADH2; DNP slimming pills were banned.
8. 8 · Close in one line. Oxidative phosphorylation couples the burning of food to the making of ATP through a proton gradient.

Scoring tip: Write both P/O values and say which is older. That shows the examiner you know the update.