Water is one of the products of aerobic cellular respiration. What is the source of the oxygen atom utilized to create the water molecules?

• A. Carbon dioxide (CO₂).
• B. Glucose (C₆H₁₂O₆).
• C. Oxygen gas (O₂).
• D. Pyruvate (C₃H₃O₃^–).

Answer: (C)

Verified step by step guidance

1. Understand the process of aerobic cellular respiration, which involves glycolysis, the citric acid cycle, and the electron transport chain.
2. Recognize that during the electron transport chain, electrons are transferred through a series of proteins embedded in the inner mitochondrial membrane.
3. Identify that oxygen gas (O2) acts as the final electron acceptor in the electron transport chain.
4. Realize that when oxygen gas (O2) accepts electrons, it combines with protons (H+) to form water (H2O) molecules.
5. Conclude that the source of the oxygen atom in the water molecules produced during aerobic respiration is the oxygen gas (O2) that is inhaled and utilized in the electron transport chain.