Question

Choose the correct sequence of electron pathway in ETS:
A. Cyt oxidase → Cyt reductase → Succinate dehydrogenase → NAD dehydrogenase.
B. NADH dehydrogenase → Succinate dehydrogenase → Cyt c reductase → Cyt. C oxidase.
C. NADH dehydrogenase → Cyt c reductase → Cyt c oxidase →O2
D. Succinic dehydrogenase → Cyt oxidase → Cyt. Reductase →O2

Answer 1

Hint:- ETS means Electron Transport System. The electron transport system is defined as the progression of complexes that move electrons from electron givers to electron acceptors using redox reaction and couples this electron move with the exchange of protons over a layer. The electron transport chain is developed of peptides, catalysts, and different particles.

Complete step-by-step solution:- Components of electron transport system:
There are four complex systems involved in this transport chain in which the electron moves from complex I and at last reaches the electron acceptor i.e., the oxygen molecule. These are the 4 major protein complexes that involve in the catalysis of redox reaction in this sequence when electron flow down the energy gradient from NADH to O2:
First, the electron moves from complex I which is composed of NADH-Q dehydrogenase.
Next, it enters into complex II which is composed of succinate dehydrogenase.
Next, it moves to complex III which is composed of cytochrome C reductase.
Next, it enters into complex IV which is composed of Cytochrome C oxidase.
And finally, the electron reaches the Oxygen molecule which serves as an electron acceptor.
This transport system comprises numerous electron carriers in the progression of cytochrome b, c, a, and a₃. The progression of electrons through the electron transport chain is an exergonic reaction.
So, the correct answer is C i.e. NADH dehydrogenase → Cyt c reductase → Cyt c oxidase →O2 not B in that case Oxygen acceptor is absent.

Note:-
When electrons flow down the energy gradient from FADH2 to O2, these 4 major protein complexes are involved in the catalysts of prefix reaction.
1. Succinate dehydrogenase is present in complex II.
2. Cytochrome c reductase complex is present in complex III.
3. Cytochrome c present in Cyt C.
4. Cytochrome c oxidase complex is present in complex IV.