Which of the following molecules provides electrons to the electron transport chain in cellular respiration?

• A. Oxygen
• B. ATP
• C. Carbon dioxide
• D. NADH

Answer: (D)

Verified step by step guidance

1. Understand the role of the electron transport chain in cellular respiration: It is a series of protein complexes located in the inner mitochondrial membrane that transfers electrons from electron donors to electron acceptors via redox reactions.
2. Identify the molecules involved in donating electrons to the electron transport chain: The primary electron donors are NADH and FADH2, which are generated during earlier stages of cellular respiration such as glycolysis, the citric acid cycle, and the oxidation of fatty acids.
3. Recognize the function of NADH: NADH is a coenzyme that carries electrons from metabolic reactions to the electron transport chain. It is oxidized to NAD+ while transferring electrons to Complex I of the chain.
4. Differentiate between the roles of the given molecules: Oxygen acts as the final electron acceptor in the electron transport chain, forming water. ATP is the energy currency of the cell, produced as a result of the electron transport chain, not a donor. Carbon dioxide is a byproduct of the citric acid cycle, not involved in electron donation.
5. Conclude that NADH is the correct molecule that donates electrons to the electron transport chain, facilitating the production of ATP through oxidative phosphorylation.