Question

Which one of the following is the terminal electron acceptor?

• A. Molecular $C{O}_2$
• B. Molecular $O_2$
• C. Molecular $H_2$
• D. $NADP{H}_2$

Answer 1

The correct option is B Molecular $O_2$

Cofactors NADH and FADH2, generated during Glycolysis and Krebs cycle, donate their electrons to the electron transport system, which is located on the inner membrane of the mitochondria and help create a proton gradient for generation of ATP.
The electron transport system is composed of 4 complexes, namely complex I - IV. Electrons received by Complex I and complex II are transferred to Complex IV via Complex III.
As a final step of the ETS, molecular oxygen receives electrons from Complex IV and gets reduced to water.
Therefore, molecular oxygen is the terminal electron acceptor of ETS.