Biology

When the mouse inhales radioactive ¹⁸O₂, the oxygen molecules will enter the body and eventually reach the mitochondria during aerobic respiration.

In the mitochondria, the ¹⁸O from the oxygen molecules will be involved in the electron transport chain, where oxygen serves as the final electron acceptor and combines with protons to form water (H₂O). This water will contain the radioactive ¹⁸O atoms.

The other statements are incorrect:

Option A: Cytoplasm and CO₂

CO₂ is produced during the Krebs cycle, but the ¹⁸O in O₂ will primarily end up in water (in the mitochondria), not in CO₂. The oxygen atoms from CO₂ come ...