Electron Transport and Oxidative Phosphorylation

Lesson 31 : Biochemical energetics and biological oxidation

Electron Transport and Oxidative Phosphorylation

While the large quantity of NADH resulting from TCA cycle activity can be used for reductive biosynthesis, the reducing potential of mitochondrial NADH is most often used to supply the energy for ATP synthesis via oxidative phosphorylation. Oxidation of NADH with phosphorylation of ADP to form ATP are processes supported by the mitochondrial electron transport assembly and ATP synthase, which are integral protein complexes of the inner mitochondrial membrane. The electron transport assembly is comprised of a series of protein complexes that catalyze sequential oxidation reduction reactions; some of these reactions are thermodynamically competent to support ATP production via ATP synthase provided a coupling mechanism, such as a common intermediate, is available. Proton translocation and the development of a transmembrane proton gradient provides the required coupling mechanism.

  1. Oxidative phosphorylation - process in which NADH and QH2 are oxidized and ATP is produced.
  2. Enzymes are found in inner mitochondrial membrane in eukaryotes.
  3. In prokaryotes, enzymes are found in cell membrane.
  4. Process consists of 2 separate, but coupled processes:

    1. Respiratory electron-transport chain

      • Responsible for NADH and QH2 oxidation
      • Final e- acceptor is molecular oxygen
      • Energy generated from electron transfer is used to pump H+ into intermembrane space from matrix ---> matrix becomes more alkaline and negatively charged.

    2. ATP synthesis

      • Proton concentration gradients represents stored energy
      • When H+ are moved back across inner mitochondrial membrane through ATP synthase ---> ADP is phosphorylated to form ATP
  1. Components of Electron Transport System

  2. Transport of molecules across mitochondrial membrane

  3. Regulation of oxidative phosphorylation

  4. Superoxide Production

Last modified: Wednesday, 25 January 2012, 11:22 AM