Elements in the Human Body and What They Do

Can you name the elements in the human body and what they do? Nearly 99% of the mass of your human body consists of just 6 chemical elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Another 5 elements make up most of the last percentage point: potassium, sulfur, sodium, chlorine, and magnesium. Here’s a look at these elements in their pure form and their function in the human body. Note that the percentage are estimates. Hydration level (how much water you drink) makes a big impact on the amount of oxygen and hydrogen in your body and affects the relative composition of the rest of the elements in your body.

Liquid oxygen is blue. (Warwick Hillier)

Liquid oxygen is blue. (Warwick Hillier)

Oxygen (O) – 65% of body weight

Atomic Number: 8

Oxygen is the most abundant element in the human body. It’s mainly found bound to hydrogen in the form of water. Water, in turn, makes up about 60% of the human body and participates in countless metabolic reactions. The element oxygen acts as an electron acceptor and oxidizing agent. It is found in all four of the major classes of organic molecules: protein, carbohydrates, lipids, and nucleic acids. Because it is a key element in aerobic cellular respiration, large amounts of oxygen are found in the lungs and in the bloodstream. Hemoglobin in blood bind the oxygen molecule, O2, from inhaled air. Oxygen is used by the mitochondria in cells to produce the energy molecule adenosine triphosphate or ATP. While it’s essential for human life, too much oxygen can be deadly, as it can lead to oxidative damage to cells and tissues.


Carbon Graphite (USGS)

Carbon Graphite (USGS)

Carbon (C) – 18% of body weight

Atomic Number: 6

Carbon is the second most abundant element in the human body and the element that is considered the basis of organic chemistry. Every single organic molecule in your body contains carbon. The element bonds to itself to form chains and ring structures that serve as the basis for all metabolic reactions in the body. Carbon in carbon dioxide is expelled as a waste product when you breathe.


Hydrogen Discharge Tube (Alchemist-hp)

Hydrogen Discharge Tube (Alchemist-hp)

Hydrogen (H) – 10% of body weight

Atomic Number: 1

Most of the hydrogen in the body is bound with oxygen to form water, H2O. Hydrogen, like carbon, is found in every single organic molecule in the body. Hydrogen also acts as a proton or positive ion in chemical reactions.


Liquid NItrogen (Cory Doctorow)

Liquid NItrogen (Cory Doctorow)

Nitrogen (N) – 3% of body weight

Atomic Number: 7

Because most of air consists of nitrogen, nitrogen gas is found in the lungs, but it is not absorbed into the body that way. Humans get nitrogen from food. The element is an important component of amino acids, which are used to build peptides and proteins. Nitrogen is also an essential component of the nucleic acids DNA and RNA and all of the other molecules derived from the nitrogenous bases.


Calcium Metal (Tomihahndorf)

Calcium Metal (Tomihahndorf)

Calcium (Ca) – 1.4% of body weight

Atomic Number: 20

About 99% of the body’s calcium is found in bones and teeth, where the element is used to build strong structural compounds, such as hydroxyapatite. Although most of the calcium is in bones and teeth, this is not the mineral’s most important function. Calcium is an important ion, used in muscle contraction and protein regulation. If any critical function has insufficient calcium, the body will actually pull it out of the bones and teeth. This can lead to osteoporosis and other problems, so it’s important to get enough dietary calcium.


Phosphorus Allotropes (Materialscientist)

Phosphorus Allotropes (Materialscientist)

Phosphorus (P) – 1% of body weight

Atomic Number: 15

Like calcium, the element and mineral phosphorus is found in the bones and teeth. The element is also found in nucleic acids and energy molecules, such as ATP (adenosine triphosphate).


Potassium (K) – 0.25%

Atomic Number: 19

Electrochemistry in the body depends on ions. Of these, the cation potassium is among the most important. Potassium is used in nerve conduction and regulating the heart beat. All cells in the body require potassium in order to function.


Sulfur (S) – 0.25%

Atomic Number: 16

Sulfur is found in several important amino acids, which are used to build proteins in the body. Sulfur is found in biotin, methionine, thiamine, and cysteine.


Sodium (Na) – 0.15%

Atomic Number: 11

Sodium, like potassium, is an essential cation. This element is important for nerve transmission and muscle function.


Chlorine (Cl) – 0.15%

Atomic Number: 17

Chlorine is an important anion. One of its functions involves the transport of the enzyme ATPase, which is used to supply energy for biochemical reactions. Chlorine is used to make hydrochloric acid, which is found in the stomach and digests food.


Magnesium (Mg) – 0.005%

Atomic Number: 12

Magnesium binds to ATP and nucleotides. Its cation is an important cofactor for enzymatic reactions. Magnesium is used to build healthy teeth and bones.


Trace elements include iron, fluorine, zinc, silicon, rubidium, strontium, bromine, lead, copper, and many more. Some trace elements are essential or have a beneficial effect on the body, while others have no known function or appear to be toxic.

Elements in the Human Body and What They Do
Last modified: October 25th, 2016 by Anne Helmenstine

6 thoughts on “Elements in the Human Body and What They Do

  1. Pingback: Nitrogen Facts - Science Notes and Projects

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