Here's why:
* Electron Transport Chain: This is the final stage of cellular respiration where electrons are passed from molecule to molecule, releasing energy that is used to generate ATP (adenosine triphosphate), the cell's primary energy currency.
* NADH and FADH2: These are electron carriers produced during earlier stages of cellular respiration (glycolysis and the citric acid cycle). They carry high-energy electrons, which they donate to the electron transport chain.
Here's a simplified breakdown:
1. Glycolysis and Citric Acid Cycle: These processes generate NADH and FADH2 by removing electrons from glucose molecules.
2. Electron Transport Chain: NADH and FADH2 deliver their high-energy electrons to the electron transport chain, embedded in the inner mitochondrial membrane.
3. Energy Release: As electrons move down the chain, energy is released. This energy is used to pump protons (H+) across the membrane, creating a proton gradient.
4. ATP Production: The protons flow back across the membrane through a protein called ATP synthase, which uses the energy to synthesize ATP.
Therefore, NADH and FADH2 are the key molecules that enter the electron transport chain, delivering the electrons needed to power ATP production.
