Question

question 18 of 50
which of the following describes the main role of the electron transport chain in cellular respiration?
a. it breaks down glucose molecules.
b. it pumps hydrogen ions inside the cell.
c. it produces the energy carriers.
d. it produces molecules of atp.

Explanation:

The electron transport chain (ETC) is the final stage of cellular respiration. In the ETC, electrons are passed through a series of protein complexes. As electrons move, hydrogen ions (\(H^+\)) are pumped across the inner mitochondrial membrane, creating a proton gradient. This gradient is used by ATP synthase to produce ATP (adenosine triphosphate), which is the energy currency of the cell.

• Option A: Glycolysis (the first stage of cellular respiration) breaks down glucose molecules, not the ETC.
• Option B: While the ETC does pump hydrogen ions (\(H^+\)) across the membrane (to form a gradient), the main role is ATP production, not just pumping ions.
• Option C: Energy carriers (like NADH and FADH₂) are produced in earlier stages (glycolysis, the citric acid cycle), not by the ETC. The ETC uses these energy carriers to produce ATP.

Answer:

D. It produces molecules of ATP.