Question

which substance is broken down during the electron transport chain? (with images: a - atp, b - h₂o, c - nadh; options: atp, water, nadh, both a and b)

Explanation:

In the electron transport chain (ETC) of cellular respiration, NADH (and FADH₂) are oxidized. NADH donates electrons, which is part of its breakdown to release energy for ATP synthesis. ATP is produced in ETC, not broken down. Water is a product, not broken down here. So NADH is the substance broken down.

Answer:

C. NADH