1. Electron Transport Chain

2. Introduction
ETC is a process in which NADH and FADH2 which are the byproducts of catabolic processes (such as glycolysis, b-oxidation, etc) and are present in their reduced form are oxidized and release energy in the form of ATP (Adinosine triphosphate).
Metabolic processes use NADH or FADH2 to transport electrons in the form of hydride ions(H-).
These electrons are passed from NADH or FADH2 to membrane bound electron carriers which are then passed on to other electron carriers until they are finally given to oxygen resulting in the production of water.

3. The transfer of electrons and protons creates an electrochemical proton gradient that derives ATP synthesis and generate chemcal energy in the form of ATP.
Complex I also known as the NADH-coenzyme Q reductase or NADH dehydrogenase.
Complex II also known as succinate-coenzyme Q reductase or succinate dehydrogenase.
Complex III also known as coenzyme Q reductase.
Complex IV also known as cytochrome c reductase.

4. Complex I (NADH-ubiquinone oxidioreductase)- It is an integral protein that receives electrons in the form of hydride ions from TCA electron carrier NADH and passes them to coenzyme Q which in ubiquinone.
It contains 42 different polypeptide chains. It has atleast 6 iron sulphur clusters.
NADH - 2e Q
NADH + 2e QH2
Ubiquinone is a small, lipid soluble molecule that carries both electrons and protons.

5. QH2 is reduced form and named as ubiquinol.
This complex is main site for the production of superoxides.

6. Complex II(succinate dehydrogenase) (Succinate-ubiquinone oxidioreductase)- It is a protein that receives electrons from succinate to yield fumarate and FADH2. From succinate the electrons are tranfered via FAD to FADH2 and then passed to ubiquinone.

7. Complex III (Ubiquinol-cytochrome c oxidioreductase)- It recieves electrons from ubiquinol and passes to cytochrome c (cyt c). Net Rxn- QH2 + 2 Cyt c(oxid) + 2Hn+ Q + 2 Cyt c(red) + 4Hp+
Crystal structure of mitochondrial cytochrome bc1 complex bound with ubiquinone

8. Complex IV (Cytochrome c oxidase)- It recieves electrons from cytochrome c and transfer them to oxygen to produce water within the mitochondria matrix. Net Rxn- 4 Cyt c(red) + 4 H+ +O2 -> 4 cyt c (red) + 2H20
The crystal structure of bovine cytochrome c oxidase in a phospholipid bilayer.

10. Net Rxn-
NADH + 11Hn+ + ½ o2 NAD+ + 10Hp+ + h2o