Dividing the human body into elements by mass
If the body of a person weighing 50 kilograms could be separated into its elements, how much of each would we get? Let's look at the percentages of the main elements by mass in the table below.
| Element | Percentage | Proportion |
|---|---|---|
| Oxygen (O) | 65% | |
| Carbon (C) | 18% | |
| Hydrogen (H) | 10% | |
| Nitrogen (N) | 3% | |
| Others | 4% |
Oxygen, carbon and hydrogen together make up about 93% of the body's mass. That means close to 46 kilograms of a 50-kilogram body comes from these three elements. The reason is that water (H2O), the largest part of the body, and the biological molecules are both built mainly from these three elements. The figure below shows this split clearly.
Extra knowledge
In which parts of the body are these elements found most? See the table below.
| Element | % by mass | Where it is found |
|---|---|---|
| O | 65 | All body fluids, tissues, bones and proteins |
| C | 18 | Every part of the body |
| H | 10 | All body fluids, tissues, bones and proteins |
| N | 3 | All body fluids, tissues and proteins |
| Ca | 1.5 | Bones, muscles, brain, lungs, kidneys, liver, heart, thyroid gland |
| P | 1.0 | Bones and urine |
| K | 0.35 | In enzymes |
| S | 0.25 | In proteins |
| Na | 0.15 | All body fluids and tissues |
| Mg | 0.05 | Muscles, brain, lungs, kidneys, liver, heart, thyroid gland |
| Cl · Fe · I | Trace | Needed only in tiny amounts, but the body cannot do without them |