Oxidative Phosphorylation (AQA A Level Biology): Revision Note

Aerobic respiration: oxidative phosphorylation

• Oxidative phosphorylation is the final stage of aerobic respiration

  • It takes place on the cristae of the inner mitochondrial membrane

  • It relies on proteins embedded in the membrane, e.g. ATP synthase enzymes

  • The large surface area of the folded cristae provides many locations for oxidative phosphorylation to occur

• During oxidative phosphorylation:

  1. hydrogen atoms are donated by reduced NAD and reduced FAD from the Krebs cycle

  2. hydrogen atoms split into protons (H⁺ ions) and electrons

  3. the electrons enter the electron transport chain; energy is released as they pass between electron carriers

     • The electron transport chain is made up of electron carrier proteins that are embedded in the inner mitochondrial membrane

  4. the released energy is used to actively transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space

  5. the protons move down their concentration gradient back to the matrix by facilitated diffusion; they move via proton channels that are associated with ATP synthase

     • This movement of protons is known as chemiosmosis

  6. ATP synthase catalyses the formation of ATP from ADP and Pi

• At the end of the electron transport chain the electrons pass to oxygen, which acts as the final electron acceptor

  • Oxygen combine with protons and electrons at the end of the electron transport chain to form water as a waste product