Oxidative Phosphorylation and Chemiosmosis

Oxidative phosphorylation is the final stage of aerobic respiration and is responsible for producing the vast majority of ATP. It takes place on the inner mitochondrial membrane and involves the electron transport chain (ETC) and the process of chemiosmosis. This lesson covers the detailed mechanism for the Edexcel A-Level Biology (9BI0) specification.

---

Overview

Oxidative phosphorylation couples two processes:

1. Electron transport — electrons from reduced NAD and reduced FAD are passed along a chain of carrier proteins, releasing energy.
2. Chemiosmosis — the energy released is used to pump H⁺ ions across the inner membrane, creating a proton gradient that drives ATP synthesis.

The final electron acceptor is molecular oxygen (O₂), which combines with H⁺ and electrons to form water.

---

The Electron Transport Chain (ETC)

The ETC consists of a series of protein complexes and mobile carriers embedded in the inner mitochondrial membrane (cristae).

Components of the ETC