Question

To develop proton gradient in respiration the required energy come from the oxidation of

• A. NADH
• B. NADH and $H_{2}O$
• C. $O_2$ and NADH
• D. $O_2$

Answer 1

The correct option is A NADH

The electron transport chain is a series of proteins and organic molecules found in the inner membrane of the mitochondria. Electrons are passed from one member of the transport chain to another in a series of redox reactions. Energy released in these reactions is captured as a proton gradient, which is then used to make ATP in a process called chemiosmosis. Together, the electron transport chain and chemiosmosis make up oxidative phosphorylation.

All of the electrons that enter the transport chain come from NADH and FADH_2 molecules produced during earlier stages of cellular respiration.

NADH is very good at donating electrons in redox reactions so it can transfer its electrons directly to complex I, turning back into $NA{D}^{+}$.

FADH_2 is not as good at donating electrons as NADH so it cannot transfer its electrons to complex I. It feeds them into the transport chain through complex II, which does not pump protons across the membrane.

So the answer is 'NADH'.