Air

From Ai Gemini:

Our atmosphere is roughly 78% nitrogen, 21% oxygen, about 1% argon, and trace amounts of other gases like carbon dioxide.

Here's what happens to the other gases when we breathe:

- Oxygen (O2): This is the gas our bodies are primarily interested in. When you inhale, air enters your lungs and reaches tiny air sacs called alveoli. These alveoli are surrounded by a network of tiny blood vessels called capillaries. Oxygen diffuses across the thin walls of the alveoli and capillaries into your bloodstream, where it binds to hemoglobin in red blood cells. This oxygen-rich blood is then pumped by the heart to all the cells in your body, which use the oxygen for cellular respiration to produce energy.

- Nitrogen (N2): Nitrogen makes up the largest portion of the air we breathe. However, our bodies generally do not utilize nitrogen gas for metabolic processes. It's largely inert. When we inhale, nitrogen enters our lungs, and a very small amount does dissolve into the bloodstream, but most of it is simply exhaled unchanged. Nitrogen acts as a diluent, preventing oxygen from being too concentrated, which could otherwise be harmful to our lung tissues over time. (Note: Under high pressure, like in scuba diving, more nitrogen can dissolve into the blood, leading to conditions like "the bends" if proper decompression isn't followed.)

- Carbon Dioxide (CO2): While we inhale a very small amount of carbon dioxide from the atmosphere, the carbon dioxide that we exhale is a waste product of our body's metabolism. Our cells produce CO2 as they use oxygen for energy. This CO2 is carried by the blood back to the lungs, where it diffuses from the capillaries into the alveoli and is then breathed out.

- Other Trace Gases (e.g., Argon, Helium, Neon): These gases are present in very small amounts in the air. Like nitrogen, they are largely inert and are not utilized by the body. They simply enter the lungs and are exhaled.

In summary, the primary goal of breathing is to bring in oxygen for cellular energy production and to expel carbon dioxide, a metabolic waste product. The other gases in the air are mostly "passengers" that are inhaled and exhaled without being actively used by the body.