Explain ETS.
Solution and Explanation
ETS or electron transport system is located in the inner mitochondrial membrane. It helps in releasing and utilizing the energy stored in NADH+H+ and FADH2. NADH + H+ , which is formed during glycolysis and citric acid cycle, gets oxidized by NADH dehydrogenase (complex I). The electrons so generated get transferred to ubiquinone through FMN. In a similar manner, FADH2 (complex II) generated during citric acid cycle gets transferred to ubiquinone. The electrons from ubiquinone are received by cytochrome bc1 (complex III) and further get transferred to cytochrome c. The cytochrome c acts as a mobile carrier between complex III and cytochrome c oxidase complex, containing cytochrome a and a3, along with copper centres (complex IV).
During the transfer of electrons from each complex, the process is accompanied by the production of ATP from ADP and inorganic phosphate by the action ATP synthase (complex V). The amount of ATP produced depends on the molecule, which has been oxidized. 2 ATP molecules are produced by the oxidation of one molecule of NADH. One molecule of FADH2, on oxidation, gives 3 ATP molecules.
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Concepts Used:
Electron Transport System
The electron transport chain or system is the sequence of electron carriers, enzymes, and cytochrome that passes electrons from one to another through the redox reaction. It is electron transport-linked phosphorylation.
It contains flavin nucleotides (FAD), nicotinamide adenine dinucleotide (NAD), coenzyme Q, and cytochromes localized in F1 particles of mitochondria. It occurs in the inner mitochondrial membrane along with cristae.
In this process five (5) complexes are involved namely, I- NADH-UQ reductase, II- Succinate-UQ reductase, III- UQH2 -cytochrome C reductase, IV- Cytochrome C oxidase, and V is connected with F0−F1 particles.
In this process, NAD and FAD are minimized.
Steps:
- Redox at complex I: Four (4) protons are pumped from the matrix to intermembrane space.
- Redox at complex II: Coenzyme Q collects the electrons from complex I and II, and goes to complex III.
- Redox of complex III: Four (4) protons are again pumped from matrix to intermembrane space and cytochrome C transports electrons to the complex IV.
- Redox of complex IV: Two (2) protons are pumped from the matrix to intermembrane space and the formation of water occurs in the matrix.
- ATP synthase action: It pumps protons from intermembrane space to matrix and generates ATP. It is associated with oxidative phosphorylation.