Aerobic Respiration: Oxidative Phosphorylation (Cambridge (CIE) A Level Biology): Revision Note

Oxidative phosphorylation

• Oxidative phosphorylation is the last stage of aerobic respiration

• It takes place at the inner membrane of the mitochondria

• Several steps occur:

  • Hydrogen atoms are donated by reduced NAD and FAD

  • Hydrogen atoms split into protons and electrons

  • The high-energy electrons release energy as they move through the electron transport chain

  • The released energy is used to transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space

  • A concentration gradient of protons is established between the intermembrane space and the matrix

  • The protons return to the matrix via facilitated diffusion through the channel protein ATP synthase

  • The movement of protons down their concentration gradient provides energy for ATP synthesis

  • Oxygen combines with protons and electrons at the end of the electron transport chain to form water

Electron transport chain

• The electron transport chain is made up of a series of membrane proteins/electron carriers

• They are positioned close together which allows the electrons to pass from carrier to carrier

• The inner membrane of the mitochondria is impermeable to hydrogen ions so these electron carriers are required to pump the protons across the membrane to establish the concentration gradient