Respiration in Plants

Electron transport system (aerobic)

  • ETC (Electron Transport chain) comprises several proton and electron acceptors that are arranged in the inner mitochondrial membrane.
  • ETC contains 4 complexes and 2 mobile carriers
  • Complex I : NADH Q reductase (largest), has FMN as the prosthetic group and it spans inner mitochondrial membrane and is able to translocate protons across it from matrix side to outer cytoplasm
  • Complex II : Succinate Q – reductase, has FAD as the prosthetic group.
  • Complex III : QH2 – Cytochrome – C reductase contains cytochrome ‘b’ and ‘c’.
  • In between complex II and III, there exist a mobile carrier called co-enzyme Q (CoQ) (or) ubiquinone (UQ).
  • Complex IV : Cytochrome ‘c’ oxidase contains cytochorme a and a3 and bound copper
  • Electron flow through complexes I, III and IV is accompanied by proton flow from the matrix to the inter membrane space.
  • The NADH formed in the cytoplasm during Glycolysis is impermeable to inner mitochondrial membrane, that must reach so that ATP may be produced.
  • Hence, a special electron carrier system, called shuttle system located in the mitochondrial membrane does the job                                  .
  • Oxidative phosphorylation is the production of energy (ATP molecules) with the help of energy liberated during oxidation of NADH and FADH2 through the enzyme ATP synthase (or) mitochondrial ATPase.
  • The enzyme consists of there parts
    (i) The head piece (or) F1 particle,
    (ii) Fo complex and
    (iii) A stalk that connects F0 and F1
  • Transport of electrons from NADH over ETS help in pushing three pairs of protons to the outer chamber and 2 pairs of protons are sent outwardly during electron flow from FADH2
  • When 2 hydrogens from the inter membrane space, move through F0 - F1 particle, due to proton motive force, the energy is used in attaching a phosphate radical to ADP by high energy bond that produces ATP.
  • Oxidation of one molecule of NADH produces 3 ATP while FADH2 oxidation forms 2 ATP molecules.

Watch this video for the topic Electron transport system (aerobic) from 4:36 to 46:10

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