oxidative phosphorylation

• chemiosmosis

  • protons move down a proton gradient
  • from intermembrane space to matrix
  • from high conc to low conc
  • this supplies energy for ATP synthase
• • ATP synthase catalyses ADP + Pi to ATP
• electron transfer chain


  • molecule donates 2 electrons to protein (molecule is oxidised)
  • electrons get passed to 2nd, 3rd proteins
  • electrons move through electron transfer chain via a series of oxidation-reduction reactions
• the final electron acceptor

  • oxidation-reduction reactions release energy
  • if ECT grinds to a halt, protons cannot be actively transported into intermembrane space
  • protons still move down proton gradient through ATP synthase until there is no more proton gradient
  • no proton gradient, no ATP produced
• final electron acceptor


  • Oxygen reacts with electrons in final protein
  • electrons react with oxygen and hydrogen to form water
  • oxygen is the final electron acceptor
  • provides energy to maintain proton gradient
• reduced NAD


  • NADH travels to matrix and donates electrons to first protein
  • NADH is oxidised so produces H+ and NAD
• reduced FAD


  • FADH2 also travels to matrix and donates 2 electrons to a smaller protein
  • produces FAD and 2 hydrogens
  • generates energy to produce ATP through ATP synthase
• FAD and NAD can be recycled to collect more protons to donate more electrons
• oxidative phosphorylation


  • NADH and FADH2 are oxidised (donate electrons)
  • electrons move through oxidation-reduction reactions
  • electrons transfer energy to proteins (proton gradient is maintained)