Important elements in living systems include oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, and iron. These elements are essential to life because of how they function within cells.
| Element |
% of Humans by Weight |
Functions in Life |
| Oxygen |
65 |
Part of water and most organic molecules; essential to physiological processes |
| Carbon |
18 |
Basic component of organic molecules |
| Hydrogen |
10 |
Part of most organic molecules and water |
| Nitrogen |
3 |
Component of proteins and nucleic acids |
| Calcium |
2 |
Component of bones; essential for nerves and muscles; blood clotting |
| Phosphorus |
1 |
Part of cell membranes and energy storage molecules; component of bones, teeth, and nervous tissue |
