Question

Which of these is the final electron acceptor in the electron transport chain?

• A. $FAD{H}_2$.
• B. $NADH$.
• C. Cytochrome C.
• D. Water.
• E. Oxygen.

Answer 1

The correct option is E Oxygen.

Electron transport chain or respiratory chain is present in the inner membrane of the mitochondrion. It is formed of different enzymes and co-enzymes which act as hydrogen and electron carriers. These electron carriers are arranged according to their increasing positive potential.

Hydrogen from NADH is first transferred to Co-Q via FMN (flavin mononucleotide). Co-Q liberates protons and electrons. Only electrons are transferred through ETS and protons (H⁺) are released into the surrounding medium. The electron than passes to cytochrome-b from Co-Q and further transferred to cytochrome-c1 and then to cytochrome-c. From cytochrome-c electrons are transferred to cytochrome-a and then to cytochrome-a3 which finally donates the electrons to free molecular oxygen. Thus oxygen acts as the last electron acceptor at the end of respiratory chain.

So, the correct answer is oxygen.