Electron transport chain?

Question

Can someone help explain or make it clear to me that a molecule in the ETC is reduced then oxidized OR oxidized then reduced. I know oxygen is the final electron acceptor. I just want to know if the molecule is oxidized or reduced first then reduced or oxidized second.

Also, is NADH oxidized or reduced to NAD+ & is NAD+ oxidized or reduced to NADH?

Thanx!

Answer 1

In the first step NADH is oxidized to NAD+ this also reduces the first member of the ETC. Then there is a chain reaction of reduction, each following member of the chain is reduced leaving the preceding one oxidized. This ends with O2 being reduced to H2O.

So to answer your question. Each member is first reduced, and in turn oxidized by the next member in the chain.