Oxygen is a colorless, odorless gas. It is a chemical element and you can find it on the periodic table with the atomic number 8. Oxygen is the third most abundant element in the universe and makes up over 20% of the earth’s atmosphere. In the human body, oxygen is the single most abundant element, making up 65% of body mass.[3] You’re breathing oxygen nearly every second of every day and it’s clearly very important. So, let’s look at a few of the ways the human body uses oxygen.
The Function of Oxygen in the Body Cellular respiration is the term used to describe the phase of the digestive process when food breaks down to supply cells with energy. During cellular respiration, cells use oxygen to break down sugar to produce ATP, or adenosine triphosphate. ATP is a molecule that supplies cells with energy. The byproducts of the process are CO2 and water.