Question

level 3
q4
what is produced when oxygen is
reduced in the electron transport chain?
a. h₂o
b. nad⁺
c. atp
d. co₂

Explanation:

In the electron transport chain, oxygen acts as the final electron acceptor. When oxygen is reduced, it combines with electrons and protons ($H^+$) to form water ($H_2O$). NAD$^+$ is regenerated in other steps (like in the oxidation of NADH), ATP is produced by ATP synthase using the proton gradient, and CO$_2$ is produced in earlier stages like the citric acid cycle, not from oxygen reduction in the ETC. So the product of oxygen reduction in the ETC is $H_2O$.

Answer:

A. $\ce{H_2O}$