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

Aerobic respiration is a metabolic process in which cells convert glucose and oxygen into energy, carbon dioxide, and water. This process occurs in several stages, including glycolysis, the Krebs cycle, and the electron transport chain, where oxygen is the final electron acceptor. Understanding this process is crucial for determining how oxygen isotopes are incorporated into cellular molecules.

Isotope labeling involves using a variant of an element that has a different number of neutrons, making it detectable through various methods. In this context, a radioactive oxygen isotope (e.g., O-18) can be tracked as it is incorporated into different molecules during metabolic processes. This technique helps identify which molecules are produced or consumed during aerobic respiration.

The main metabolic products of aerobic respiration include carbon dioxide (CO2), water (H2O), and energy-rich molecules like NADH. During the process, oxygen is used to oxidize substrates, leading to the formation of these products. Identifying which of these molecules would be radiolabeled helps in understanding the pathways and transformations occurring during respiration.