Which of the following molecules is a source of electrons donated to the electron transport chain in cellular respiration?

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

Answer: (A)

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 the electron transport chain: The main electron donors are NADH and FADH2, which are generated during earlier stages of cellular respiration such as glycolysis and the citric acid cycle.
3. Recognize the function of NADH: NADH is a key electron carrier that donates electrons to the electron transport chain, specifically to Complex I, initiating the process of electron transfer.
4. Differentiate between the given options: Carbon dioxide is a waste product of cellular respiration, ATP is the energy currency produced, and oxygen is the final electron acceptor in the chain, not a donor.
5. Conclude that NADH is the correct answer as it donates electrons to the electron transport chain, facilitating the production of ATP through oxidative phosphorylation.