Question

Last electron acceptor during ETS is-
A) $O_2$
B) Cyt a
C) Cyt $a_2$
D) Cyt $a_3$

Answer 1

Hint: A series of complexes that transfer electrons from electron donors to electron acceptors through redox reactions is called the electron transport chain.

Complete Answer:
- In this, electron transfer is coupled with the transfer of protons across a membrane. Various peptides, enzymes, and other molecules are involved in the electron transport system.
The process of electron transport is exergonic.
- The redox reactions create energy which generates an electrochemical proton gradient which is responsible for synthesis of adenosine triphosphate (ATP).
- The flow of electrons terminates when molecular oxygen accepts the final electron, this is called aerobic respiration. In anaerobic respiration, other electron acceptors are used.
- The Gibbs free energy state of the components drives the redox reactions in the electron transport chain.
- Gibbs free energy and redox potential are related quantities. The energy of the redox reactions produced on transfer of electrons from a low redox potential to a higher redox potential is harvested by the complexes of the electron transport chain, this creates an electrochemical gradient.
- The electrochemical gradient drives the synthesis of ATP by coupling oxidative phosphorylation with ATP synthase.

Thus, the correct answer is A $O_2$.

Note: Electron transport chain is different for animals, plants and bacteria. In aerobic respiration, oxygen is the last electron acceptor. The electron transport chain on completion results in formation of ATP.