gen-define-oxidative-phosphorylation-and-give-one-short-worked-e-4522

Define oxidative phosphorylation and give one short worked example.

# Oxidative Phosphorylation **Definition:** Oxidative phosphorylation is the metabolic process in which cells use enzymes to oxidize nutrients (through the electron transport chain), thereby releasing energy that is used to synthesize ATP from ADP and inorganic phosphate. This occurs in the inner mitochondrial membrane and is the final stage of cellular respiration. ## Key Components: 1. **Electron Transport Chain (ETC)** - transfers electrons through protein complexes 2. **Chemiosmosis** - creates a proton gradient across the membrane 3. **ATP Synthase** - uses the gradient to phosphorylate ADP to ATP --- ## Worked Example: **Question:** If one NADH molecule enters the electron transport chain, approximately how many ATP molecules are produced? **Solution:** 1. **NADH donates electrons** to Complex I of the ETC 2. **Proton pumping occurs:** - Complex I pumps 4 H⁺ - Complex III pumps 4 H⁺ - Complex IV pumps 2 H⁺ - **Total: ~10 H⁺ pumped into intermembrane space** 3. **ATP synthesis:** - ATP synthase requires ~4 H⁺ to produce 1 ATP (3 for synthesis + 1 for transport) - 10 H⁺ ÷ 4 H⁺/ATP = **~2.5 ATP per NADH** **Answer:** One NADH produces approximately **2.5 ATP** through oxidative phosphorylation. *(Note: FADH₂ produces ~1.5 ATP as it enters at Complex II)*