Energy Production in Cells – ETC

Summary: A series of protein complexes embedded in the inner mitochondrial membrane. Electrons captured from donor molecules are transferred through these complexes. Coupled with this transfer is the pumping of hydrogen ions (protons) across the inner mitochondrial membrane. This proton gradient is used by ATP synthase to make ATP.









  1. NADH Dehydrogenase
    • Takes 2 electrons from NADH (donor molecule)
    • Pumps 2 protons across membrane
  2. Ubiquinone
    • Transfers 2 electrons from NADH Dehydrogenase to Cytochrome b-c.
  3. Cytochrome b-c
    • pump a proton across the membrane for each electron given to cytochrome c
  4. Cytochrome c
    • Transfer electrons individually from cytochrome b-c, to cytochrome oxidase
  5. Cytochrome Oxidase
    • react 4 electrons, 1 oxygen molecule and 8 protons to form 2 water molecules
    • pumps remaining 4 protons across membrane
  6. ATP Synthase
    • uses the protein gradient to spin the molecule like a turbine
    • this alters the molecules shape. This change facilitates the bonding of ADP and inorganic phosphate to form ATP
    • The transfer of 3 protons across the membrane, down its gradient, produces 1 ATP molecule.

The majority of ATP in cellular respiration is made through the Electron transport chain.