- Synthesis of ATP is associated with the electron transport chain on the membranes of mitochondria and chloroplasts
- 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
Examiners often ask why oxygen is so important for aerobic respiration. Oxygen acts as the final electron acceptor. Without oxygen, the electron transport chain cannot continue as the electrons have nowhere to go. Without oxygen accepting the electrons (and hydrogens), the reduced coenzymes NADH and FADH2 cannot be oxidised to regenerate NAD and FAD, so they can’t be used in further hydrogen transport.