Elements in the Human Body and What They Do

The elements found in the human body

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Ninety-nine percent of the mass of the human body is made up of only six chemical elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Every organic molecule contains carbon. Since 65 to 90 percent of each body cell consists of water (by weight), it isn't surprising that oxygen and hydrogen are major components of the body.

Oxygen

Liquid oxygen

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Oxygen is present in water and other compounds. This element is necessary for respiration. You will find it in the lungs because about 20% of the air you breathe is oxygen. Oxygen accounts for about 65% of the mass of the human body.

Carbon

Carbon

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Carbon is found in every organic molecule in the body. The reason it forms the basis for organic life is that each carbon atom offers four sites for chemical bonding and allows new bonds to be formed or broken without expending too much energy. This makes carbon a good building block, particularly for long polymeric molecules.

Carbon is ingested through the food we eat and the air we breathe. The element accounts for 18.6% of the total mass of the human body. When we exhale, we expel carbon in the form of carbon dioxide.

Hydrogen

Hydrogen atoms, the stuff from which stars are made
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Hydrogen is a component of the water molecules in the body, as well as most other compounds. It is the third most abundant element in the human body.

Nitrogen

Liquid nitrogen looks like boiling water
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Nitrogen is a component of proteins, nucleic acids, and other organic compounds. It makes up about 3% of the body's mass.

Nitrogen gas is found in the lungs since most of the air you breathe consists of this element. The human body cannot use this nitrogen, though. You need to eat foods that contain it to obtain this element in a usable form.

Calcium

Calcium in a protective Argon Atmosphere

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Calcium is a major component of the skeletal system, as it's found in bones and teeth. Calcium accounts for 1.5% of the body's mass.

Calcium is also found in the nervous system, muscles, and the blood where it is integral to proper membrane function, conducting nerve impulses and regulating muscle contractions and blood clotting.

Phosphorus

Phosphorus is in every cell nucleus
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Phosphorus is found in the nucleus of every cell. About 1% of the human body consists of phosphorus.

Phosphorus is part of nucleic acids, energy compounds, and phosphate buffers. The element is incorporated into the bones, where it combines with other elements such as iron, potassium, sodium, magnesium, and calcium. Phosphorus is necessary for sexual function and reproduction, muscle growth, and the delivery of nutrients to the nerves.

Potassium

Raw potassium
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Potassium is primarily found in the muscles and nerves as an ion. The body is made up of 0.25% potassium.

Potassium is important for membrane function, nerve impulses, and muscle contractions. Potassium cations are found in cellular cytoplasm. The electrolyte helps to attract oxygen and remove toxins from tissues.

Sodium

Rock salt crystals (sodium chloride)

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Sodium is essential for proper nerve and muscle function. It is excreted in perspiration. The human body is about 0.15% sodium.

Chlorine

An illustration of chlorine
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Chlorine aids in cellular absorption of water. It is the major anion in body fluids. Chlorine accounts for approximately 0.15% of the body.

Chlorine is a part of hydrochloric acid, which is used to digest food. It is involved in proper cell membrane function.

Magnesium

Magnesium accounts for 0.05% of body weight
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Magnesium is a cofactor for enzymes in the body. It is a trace element, present at around 0.05% abundance. Although it makes up only a small part of the human body, magnesium is necessary for strong teeth and bones.

Sulfur

Museum minerl series: Native sulphur from Sicily, Italy. 9cm across.
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Sulfur is a component of many amino acids and proteins, which are necessary for muscle growth. About 0.25% of human body mass is sulfur.

Iron

Iron is found in hemoglobin
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Iron is a trace element, accounting for about 0.006% of human body mass. It is found in hemoglobin, where it acts as an oxygen carrier. The metal is important for metabolism as well.

Other Elements

Copper minning ore

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There are 12 minerals deemed essential for proper human nutrition: calcium, iron, phosphorus, iodine, magnesium, zinc, selenium, copper, manganese, chromium, molybdenum, and chlorine. Sodium, potassium, and sulfur are also essential but aren't categorized in the same group by the FDA.

Zinc (0.0032% of the human body) forms what are called "zinc fingers" in proteins, which regulate genes. Copper (0.0001%) acts as an electron donor, helping iron function properly.