Question

What is the most significant feature of enzyme complex 3 of the electron transport chain?

Answer 1

Electron transport system:

1. ETS or electron transport system involves a series of complex reactions, by which the electron is transported to the last final electron acceptor which is oxygen. that takes place in the inner mitochondrial membrane.
2. ETS takes place in the inner mitochondrial membrane.
3. Electron transport takes place with help of reduced coenzymes like NADH₂ and FAD.
4. Oxygen after accepting the electron turns reactive and undergoes the reduction with the protons present in the matrix.
5. Later this combination forms metabolic water.

Importance of complex III:

1. Complex III is also called cytochrome bc1 complex.
2. It is a third complex in the electron transport chain.
3. It consists of cytochrome b, cytochrome c1 and Rieske Iron-Sulfur Protein.
4. The cytochrome bc1 complex is also called quinol-cytochrome c reductases.
5. Complex III is formed of 11 polypeptide subunits, only 1 of which (cytochrome b) is constructed by the mitochondrial genome.
6. The bc1 complexes are intrinsic membrane proteins.
7. Complex III carries out a multistep process called oxidative phosphorylation and plays an essential role in the biochemical generation of ATP.
8. It helps in the oxidation of ubihydroquinone and the reduction of cytochrome c in ETS and bacterial photosynthetic and respiratory chains.
9. It gets inhibited by antimycin A.
10. Antimycin A arrests the transfer of electrons from either complex I or FADH₂-containing flavoproteins to cytochrome c.
11. In this case, elements foregoing complex III become fully reduced, and those after it become oxidized.