Electron Transport Chain

Cellular Metabolism - CH19 and 20
Cell Metabolism

Takes unsusable products form metabolism and creates into something usable: ATP

Electron Transport Chain/Respiratory Chain

• When taken together the ETC and F1F0 ATPase has both substrate level phosphorylations and oxidative phosphorylations respectively

Function/Purpose:

• Converts the NADH and FADH2 used in the anabolized from metabolic catabolism into ATP

Fundamentals:

• Oxidative Phosphorylation

LOC:

• Mitochondria - on the inner mitochondrial membrane
  • Affects the intermembrane space

Components:

• C1) NADH:Ubiquinone Oxidoreductase/NADH-Q reductase/Site 1
  • NADH Dehydrogenase
  • NADH+H
  • Reduced NADH+H passes 2 electrons to FMN (PROSTHETIC GROUP)
  • Reduced FMNH2 passes electrons to iron-sulfur clusters (Fe-S) = Ferrous (Fe2) to Ferric (Fe3)
  • Electrons passed to Coenzyme Q -- CoQH2
• C2) Succinate:Ubiquinone Oxodoreductase/Succinate-Q reductase/Complex 2
  • Succinate Dehydrogenase - TCA enzyme!
  • FADH2
  • Reduced HADH2 passes 2 electrons to iron-sulfur clusters (Fe-S)
  • Electrons passed to Coenzyme Q --> CoQH2
  • C1 and C2 transfer electrons to Ubiquinone (Q)--> Ubiquinol
  • Reduced Ubiquinol transfers electrons to C3
• C3) Ubiquinol Cytochrome C Oxidoreductase/Cytochrome reductase/Site 2
  • Cytochrome bc1 Oxidoreductase complex
  • Cytochrome
    • Reduced C3 transfers electrons to Cytochrome c
    • Cytochrome c transfers electrons to C4
• C4) Cytochrome C Oxidase/Cytochrome oxidase/Site 3
  • Cytochrome
  • Cytochrome aa3 Oxidoreductase complex
• C5) F1F0 ATP Synthase
  • Converts the proton gradient established in the intermembrane space of the mitochondria to be converted into ATP

Summary:

• 36-38 ATP Generated
  • 8 NADH+H -> 24 ATP (P/O Ratio)
    • Pyruvate DH X2 (because of GAP and DHAP)
    • Isocitrate DH X2 (because of GAP and DHAP)
    • a-keto DH X2 (because of GAP and DHAP)
    • Malate DH X2 (because of GAP and DHAP)
  • 2 FADH2 -> 4 ATP (P/O Ratio)
    • Sucinate DH X2 (because of GAP and DHAP)
  • 2 NET ATP from Glycolysis
    • Pyruvate Kinase X2 = +1ATP
    • Phosphoglycerate Kinase X2 = +1ATP
    • Hexokinase = -1ATP
    • Phosphofructokinase = -1ATP
  • 2 GTP from TCA Cycle -> 2 ATP
    • Succinate CoA Sythetase = GTP -> ATP

Concepts:

• Redox Chemistry - Oxidation Reduction
• Q = Ubiquinone
  • Oxidized quinone is ubiquinone while Reduced quinone is dihydroxyquinone/ubiquinol
  • Semiquinone is free radical intermediate
• P/O Ratio - Mitochondria
• Phosphorylation

Terminology:

• Cytochrome: electron carriers between CoQ and Oxygen
  • Electron transporting proteins that contain heme prosthetic groups with an iron with alternating Ferrous and Ferric conditions

Additional Information

• Wikipedia