Explain ETS.
The mechanism of the Electron transport system is as follows: Glucose is completely oxidized towards the end of the citric acid cycle. Energy is not released unless NADH and FADH are oxidized through ETS. The ETS is operative in the inner mitochondria membrane. Electrons from NADH produced in the mitochondrial matrix are oxidized by an NADH dehydrogenase (complex I) and electrons are then transferred to ubiquinone located within the inner membrane also receives reducing equivalents via FADH which is generated during oxidation of succinate, through the activity of an enzyme named succinate dehydrogenase (complex II). Reduced ubiquinone is then oxidized with the transfer of electrons to cytochrome complex (complex III). Cytochrome is a small protein attached to the outer surface of the inner membrane and acts as a mobile carrier for the transfer of electrons between complex III and complex IV. (complex IV) is cytochromes ‘c’ oxidize complex having cytochromes ‘a’ and a3. When electrons pass from one carrier to another via complex I to IV in ETS, they are coupled to ATP synthase (complex V) for the production of ATP from ADP and inorganic phosphate. Oxidation of one molecule of NADH, gives rise to 3 molecules of ATP, while that of FADH, produces 2 molecules of ATP. Electrons are curried by cytochromes and recombine with their protons before the final stage when the hydrogen atom is accepted by oxygen to form water. O2 acts as the final hydrogen acceptor. The whole process by which oxygen allows the production of ATP by phosphorylation of ADP is called ‘oxidative phosphorylation’.
