4.2 Electron Transport Chain

  • Electrons (with their hydrogens) are passed from one molecule to the next in order of increasing electronegativity

  • Energy is released with each transfer

  • O2 is the final electron acceptor

  • This energy is used to pump H+ across from matrix to intermembrane space, setting up an electrochemical gradient of protons

    • Proton gradient
    • Proton-motive force (back down to low electronegativity through ATP synthase)
    • Will be used to form ATP through OP

    Electron Transport Chain

IN DETAIL

  • 1st Oxidation
    • NADH dehydrogenase oxdized NADH to NAD+
    • Energy released drives H+ from matrix into intermembrane space
  • 2nd & 3rd Oxidation
    • Succinate dehydrogenase oxdizes FADH2
    • Ubiquinone oxidizes NADH dehydrogenase ans Succinate dehydrogenase
    • UQ is hydrophobic, shuttles within bilayer
    • uses electrons to move H+ across membrane
  • 4th & 5th Oxidation
    • Cytochrome complex oxidizes UQ
    • Cyt C oxidizes Cytochrome complex
    • cyt c is hydrohphillic, shuttles in the intermembrane space
  • 6th & 7th Oxidation
    • Cytochrome oxidase oxidizes Cyt C
    • Oxygen oxidizes cytochrome oxidase
    • energy released pumps H+ across the membrane
  • 8th Reaction
    • Proton gradient sets up proton-motive force
    • only way back is with ATP synthase
    • Flow of protons allows the energy to synthesize ATP
    • Chemiosmosis
    • OP