If you were to expose cells that are undergoing aerobic cellular 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

Water

Explanation:

Molecular oxygen is the terminal electron acceptor and serves to receive electrons from reduced NADH and FADH2 to reoxidize them. NADH and FADH2 are formed during glycolysis and Kreb's cycle. These reducing powers should be re-oxidized to enter in the first two steps of aerobic respiration again.

For the purpose, NADH, and FADH2 transfer their electrons to the molecular oxygen via electron transport chain. After accepting the electrons, molecular oxygen is oxidized into the water molecule. Therefore, radioactive oxygen isotope would appear in the form of a water molecule after completion of cellular respiration.