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

  

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