Here's why:

* Electron Transport Chain: This process is a key part of cellular respiration, where energy is extracted from food molecules (like glucose) and stored in ATP.

* Electron Flow: Electrons are passed along a series of protein complexes embedded in the inner mitochondrial membrane.

* Energy Release: As electrons move, energy is released and used to pump protons across the membrane, creating a proton gradient.

* Oxygen's Role: Oxygen acts as the final electron acceptor, combining with protons to form water (H2O).

Without oxygen, the electron transport chain would stop, and ATP production would cease. This is why oxygen is essential for aerobic respiration.