What is Electron transport chain?

Although the glucose molecule, after glycolysis and the Krebs cycle, has been completely oxidized and produced energy in the form of ATP, most of the energy is in the electrons that accepted NAD + and FAD, which were reduced to NADH and FADH 2.

The NADH and FADH 2 have great reducing power and transfer their electrons to molecular oxygen (O2) through an electron transport chain or respiratory chain. In the transport of these electrons, a large amount of energy is released that is used to form ATP ( oxidative phosphorylation ). 


Electronic transport

The electrons of the NADH and FADH 2 molecules, with a high energy level, pass through different transporter molecules down a gradient of redox potentials until they reach O 2, which is the final electron acceptor.    

These transporter molecules, in the inner mitochondrial membrane, are reduced and oxidized, accepting electrons and giving them to the next molecule, lowering the electrons from high energy levels to lower ones. When lowering to other levels, energy is released that will be used in the synthesis of ATP by oxidative phosphorylation.

The electron transporting molecules of the respiratory chain are grouped into four large supramolecular complexes located in the inner mitochondrial membrane :  

  • Complex I or NADH- dehydrogenase Complex.
  • Complex II or Ubiquinone or Coenzyme Q reductase.
  • Complex III or Cytochrome b-c1 complex.
  • Complex IV or Cytochrome oxidase complex.

What is Electron transport chain? Electron transport chain 1