Here's why:

* Cellular Respiration: This is the process by which your body converts food (glucose) into usable energy (ATP).

* Oxygen's Role: Oxygen acts as the final electron acceptor in this process, allowing the breakdown of glucose to continue and generate ATP. Without oxygen, cellular respiration would stop, and your body wouldn't be able to extract energy from food.

Think of it like this: Oxygen is like the fuel for the fire that burns the food to release energy.