Electron Transport Chain

Electron transport chain

electron transport chain

Electron transport: pumps protons into intermembrane space

  • Complex I
    • Receives electrons from NADH.
    • Transfers electrons to CoQ.
    • Inhibited by rotenone, amytal.
  • Complex II
    • Receives electrons from FADH2.
    • Transfers electrons to CoQ
  • Coenzyme Q
    • Also called ubiquinone, or CoQ.
    • Transfers electrons to complex III.
  • Complex III
    • Transfers electrons to cytochrome c.
    • Inhibited by antimycin A.
  • Cytochrome c
    • Transfers electrons to complex IV.
  • Complex IV
    • transfers its electrons to oxygen, forms water.
    • Inhibited by CN-

Oxidative phosphorylation: uses proton gradient to make ATP

  • Complex V, also called ATP Synthase.
  • Oxidative phosphorylation occurs here, turning ADP to ATP.
  • Uses the proton gradient generated by electron transport.
  • Inhibited by oligomycin.
  • 2,4-DNP, aspirin, thermogenin increases membrane permeability. Causes proton gradient to leak through membrane rather than fuel ATP synthase.

Aerobic Cellular Respiraction: Glucose + 6O2 → 6CO2 + 6H2O

  • Glycolysis: Glucose → 2 Pyruvate (2ATP, 2NADH)
    • Net 2 ATP
    • 2 NADH
  • Krebs Cycle: 2 Pyruvate → 6 CO2 (8NADH, 2FADH2, 2GTP)
    • 3 CO2 per pyruvate.
    • 4 NADH per pyruvate.
    • 1 FADH2 per pyruvate.
    • 1 GTP per pyruvate.
    • At the end of the Krebs cycle, the C6 glucose has been fully oxidized to 6 molecules of CO2.
  • Electron transport chain: 6O2 → 6H2O (28ATP)
    • 3 ATP per NADH.
    • 2 ATP per FADH2.
  • Summary: 36 ATP + 2 GTP per glucose.
    • Glycolysis: 2 ATP.
    • Krebs Cycle: 2 GTP.
    • ETC: 34 ATP.
      • 2 NADH from glycolysis: 2 x 3 = 6 ATP.
      • 8 NADH from Krebs cycle: 8 x 3 = 24 ATP.
      • 2 FADH2 from Krebs cycle: 2 x 2 = 4 ATP.

Mitochondrial transport

  • Glycerol phosphate shuttle: NADH → mitochondria: 2ATP/NADH, found in most cells with mitochondria, regenerates cytosolic NAD+
  • Malate-aspartate shuttle: NADH → mitochondria: 3ATP/NADH, found in heart, regenerates cytosolic NAD+
  • Oxaloacetate out of mitochondria by conversion to either malate (malate DH) or aspartate (aspartate aminotransferase).
  • Tricarboxylate transport system: Acetyl CoA out of mitochondria. Mechanism: transport citrate (made from acetyl CoA and oxaloacetate) into the cytosol, where it's broken back down to acetyl-CoA and oxaloacetate.
  • ATP-ADP translocator: ATP out of mitochondria, ADP into mitochondria, driven by membrane potential.
    • Atractyloside and Carboxyatractyloside inhibit translocator on the external surface.
    • Bongkrekic acid inhibits translocator on the internal surface.
  • Phosphate carrier: returns inorganic phosphate back into the mitochondria.