If you were to expose cells that are undergoing aerobic respiration to a radioactive oxygen isotope in the form of O2, which of the following molecules would you expect to be radiolabeled? a. pyruvate b. water c. NADH d. CO2

Verified step by step guidance

1. Understand the role of oxygen in aerobic respiration: Oxygen is the final electron acceptor in the electron transport chain, which is a part of aerobic respiration. It reacts with electrons and protons to form water.
2. Identify where oxygen is used in cellular respiration: Oxygen is used in the electron transport chain, specifically at the complex IV, where it gets reduced to form water.
3. Analyze the options given in relation to the use of oxygen: Among the options, water (H2O) is the direct product of the reduction of oxygen, making it the molecule that would incorporate the radioactive oxygen isotope.
4. Eliminate other options: Pyruvate is formed in glycolysis, NADH is a carrier of electrons and protons but does not incorporate oxygen, and CO2 is released during the citric acid cycle but does not directly involve molecular oxygen.
5. Conclude that the correct answer is: b. water, as it is the molecule that would be radiolabeled when cells undergoing aerobic respiration are exposed to a radioactive oxygen isotope.