In an experiment, mice were fed glucose (C₆H₁₂O₆) containing a small amount of radioactive oxygen. The mice were closely monitored, and after a few minutes, radioactive oxygen atoms showed up in __________.

• A. NADH
• B. water
• C. ATP
• D. oxygen gas
• E. carbon dioxide

Answer: (E)

Verified step by step guidance

1. Begin by understanding the process of cellular respiration, where glucose (C6H12O6) is broken down to produce energy in the form of ATP, and involves the consumption of oxygen and production of carbon dioxide and water.
2. Recall that during cellular respiration, glucose undergoes glycolysis, the Krebs cycle, and oxidative phosphorylation. Oxygen is used in the electron transport chain, where it acts as the final electron acceptor to form water.
3. Consider the fate of oxygen atoms in the glucose molecule. In the Krebs cycle, carbon atoms from glucose are released as carbon dioxide (CO2). If the oxygen in glucose is radioactive, it will be incorporated into the carbon dioxide produced.
4. Understand that NADH and ATP are products of cellular respiration but do not directly incorporate oxygen atoms from glucose. Oxygen gas is not produced in cellular respiration; it is consumed.
5. Conclude that the radioactive oxygen atoms from glucose would appear in carbon dioxide, as the oxygen atoms are released during the conversion of glucose to CO2 in the Krebs cycle.