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 the breakdown of glucose (C6H12O6) in the presence of oxygen (O2) to produce carbon dioxide (CO2), water (H2O), and energy in the form of ATP.
2. Identify the stages of aerobic respiration: glycolysis, the citric acid cycle (Krebs cycle), and the electron transport chain (ETC).
3. Focus on the electron transport chain, where oxygen plays a crucial role as the final electron acceptor.
4. Recognize that during the electron transport chain, electrons are transferred through a series of proteins, and oxygen (O2) accepts these electrons at the end of the chain.
5. Understand that when oxygen accepts electrons, it combines with protons (H+) to form water (H2O), making oxygen gas (O2) the source of the oxygen atom in water molecules produced during aerobic respiration.