Answer to Question #168769 in Cell Biology for Peyton Alison

Question

Why is it important for NADH and FADH2 to donate their high energy electrons to NADH-Q reductase and Quinone, respectively?  Would it not be easier to donate the electrons directly to oxygen since that’s where they are going to end up anyway? 

Answer 1

FADH2 And NADHs accepted by protein complex NADH-Q reductose. It is the largest electron carrier constiting more than 22 protein chains. Ubiquinone has a higher reduction potential. Ubiquinone is an organic molecule that dissolves in hydrophic region of inner membrane of the mitochondria.NADH-Q reductose complex accepts electrons from NADH and passes the electron to ubiquinone.The free energy released by the spontaneous transfer of electrons from the NADH-Q reductase complex to ubiquinone is used for a very important purpose. The energy is used to pump electrons out of matrix through NADH-Q reductose and into intermembrane space building up significant proton-concentration gradient. This proton gradient provides the energy needed to generate ATP.NADH-Q reductase acts as both an electron carrier and a proton pump while ubiquinone is an electron carrier only.

It would not be easier to donate electrons directly to oxygen because ATP synthesis is not an energetically favorable reaction and energy is needed for it to occur. This energy is derived from the oxidation of NADH and FADH2 by the four protein complexes of the electron transport chain.