During aerobic respiration, electrons travel downhill in which sequence?

A) food - -> Krebs cycle - -> ATP - ->NAD+

B) food - -> NADH - -> electron transport chain - -> oxygen

C) glucose - -> ATP - -> oxygen

D) glucose - -> ATP - -> electron transport chain - -> NADH

E) food - -> glycolysis - -> Krebs cycle - -> NADH - -> ATP

The correct answer will be option-B.

Explanation:

Cellular respiration is a slow process which produces energy from the oxidation of food components which could be glucose, fatty acids and proteins.

The process proceeds in four steps: glycolysis, link reaction, Krebs cycle and electron transport chain.

The energy molecules are produced when a high energy electron gets reduced and the released energy is stored in the form of energy molecules which could be ATP or energy equivalents like NADH and FADH₂.

These reducing equivalents donate its electrons during electron transport chain where the electrons flow to the last electron acceptor called oxygen.

Thus, Option-B is the correct answer.