CIE A Level Biology (9700) 2019-2021

Revision Notes

12.1.4 The Electron Transport Chain

The Electron Transport Chain

  • 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

Exam Tip

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.

Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.
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