The Electron Transport Chain

  • The final stage of respiration, forming ATP and H2O
    • The other steps of respiration create some ATP but not as much as this stage
  • It takes place across the inner mitochondrial membrane

  1. NADH and FADH from the Krebs Cycle break down into NAD and FAD, releasing hydrogen
  2. These hydrogen atoms are broken down into H+ ions and electrons
  3. The electrons move down the chain of electron carriers in the mitochondrial membrane (the electron transport chain) and release energy as they do so
  4. This energy is used to pump the H+ ions across the membrane against their concentration gradient
  5. The H+ ions diffuse back across the membrane through the ATP synthase enzyme channel
  6. This movement provides energy for the enzyme to combine ADP and Pi to form ATP
  7. The H+ ions and the electrons from the electron transport chain combine with O2 to form H2O
  • Glucose is not the only respiratory substrate – lipids and amino acids break down to form molecules that enter the Krebs Cycle and are used for respiration.

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