system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why do we need Oxygen to live?

I get food and water, they are converted from one energy source to another, but what does oxygen do?
gpt
Oxygen is what allows you to actually get energy out of the food you eat.  Your body combines oxygen with sugars, amino acids, etc from the food you eat to produce ATP (adenosine triphosphate), which is used as an energy source by your cells.