1.4.6 Oxidative phosphorylation and chemiosmosis

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  • Created by: JTY3
  • Created on: 21-04-16 14:56
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  • Oxidative phosphorylation an chemiosmosis
    • The final stage of aerobic respiration.
      • Involves electron carriers embedded in the inner mitochondrial matrix which are folded into cristae.
      • Reduced NAD and FAD are reoxidised when they donate hydrogen atoms to the electron carriers.
        • The hydrogen atoms are split into protons and electrons.
      • The first electron carrier to accept electrons from reduced NAD is a protein complex (complex I) called NADH
        • The protons into solution in the matrix.
    • Electron transport chain
      • Electrons are passed along a chain of electron carriers then donated to molecular oxygen, the final electron acceptor.
    • Chemiosmosis
      • As electrons flow along the chain, energy is released.
        • It is used by coenzymes associated with complexes I, III and IV to pump protons across to the intermembrane space.
          • This builds up a proton gradient which is also a pH gradient and an electrochemical gradient.
            • Potential energy builds up in the intermembrane space.
              • The hydrogen ions can diffuse through  ion channels in the membrane
                • The flow of hydrogen ions is chemiosmosis
    • Oxidative phosphorylation
      • The formation of ATP by the addition of inorganic phosphate to ADP in the presence of oxygen
        • As protons flow through an ATP synthase enzyme, they drive the rotation of part of the enzyme.
          • This joins ADP and P to make ATP.
            • The electrons are passed on to molecular oxygen- the final electron acceptor.
              • Hydrogen ions also join so that the oxygen is reduced to water.
      • How much ATP is made?
        • 10 NAD can produce 26 ATP during oxidative phosphorylation
          • With ATP made during glycolysis and the Krebs cycle the total yeild of ATP per molecule of glucose respired should be 30 molecules.
            • This is rarely achieved due several reasons.
              • Proton leak across the mitochondrial membrane.
              • Some ATP produced is used to actively transport pyruvate over the membrane
              • Some ATP is used for the shuttle to bring hydrogen from reduced NAD from glycolysis into the mitochondria.


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