Oxidative Phosphorylation

I. Introduction to Oxidative Phosphorylation

  • Oxidative phosphorylation is the final stage of cellular respiration where the energy from electrons transferred along the electron transport chain is used to form ATP.

  • It occurs in the inner mitochondrial membrane and involves two main processes: the electron transport chain and chemiosmosis.

  • During oxidative phosphorylation, oxygen acts as the final electron acceptor and is reduced to form water.

II. Electron Transport Chain

  • The electron transport chain is a series of large protein complexes located in the inner mitochondrial membrane.

  • Electrons derived from NADH and FADH2 are transferred along these complexes.

  • As the electrons are transferred, protons (H+ ions) are actively transported from the mitochondrial matrix to the intermembrane space, generating a proton gradient.

III. Chemiosmosis

  • In the process of chemiosmosis, the stored energy in the proton gradient drives the ATP synthase, a transport protein that synthesizes ATP.

  • The movement of protons back across the membrane into the matrix provides the energy for the phosphorylation of ADP to ATP.

  • This is known as oxidative phosphorylation as it involves the oxidation of NADH and FADH2 and the transfer of a phosphate group to ADP.

IV. Importance of Oxygen

  • Oxygen is essential for oxidative phosphorylation as it acts as the terminal electron acceptor in the electron transport chain.

  • The reduction of oxygen to water ensures that the electrons are safely disposed of at the end of the electron transport chain making sure the process can continue.

  • If oxygen was not present, the electron transport chain would halt, and ATP production would be severely reduced.

V. ATP Yield

  • The number of ATP molecules produced during oxidative phosphorylation varies, but it is thought to be around 28-34 ATP molecules per glucose molecule.

  • This means oxidative phosphorylation is responsible for the majority of the ATP produced during cellular respiration, which illustrates its importance in providing energy for biological processes.