As our knowledge of the chemistry of living systems (biochemistry) increases, we learn more about essential elements. Mammals like ourselves are thought to use only 25 of the 116 known elements.
Apart from oxygen, these elements are not found as ‘pure’ elements. Instead, they are found either dissolved in water in an ionic form, such as sodium ions and chloride ions, or as parts of large molecules, such as haemoglobin.
What elements are present in the human body?
Scientists believe that about 25 of the known elements are essential to life. Just four of these – carbon (C), oxygen (O), hydrogen (H) and nitrogen (N) – make up about 96% of the human body.
These four elements are found in the basic structure of all biochemical molecules. For example, glucose is a carbohydrate and its molecular formula is C6H12O6 – each molecule of glucose is made up of 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms.
The other elements found can be divided into two main groups – major elements and trace elements.
The human body functions as a result of a large number of chemical reactions involving compounds of all of these elements.
Trace elements are important
Although many of the elements are required in only very small amounts, they do play a very important role in keeping the body working effectively:
- Much of the 3–4 grams of iron in the body is found in haemoglobin, the substance responsible for carrying oxygen from the lungs to the rest of the body.
- The body has about 75 mg of copper, about one-third of which is found in the muscles. Copper combines with certain proteins to produce enzymes that act as catalysts to help a number of body functions. Some are involved in the transformation of melanin for pigmentation of the skin, and others help to form cross-links in collagen and elastin and thereby maintain and repair connective tissues. This is especially important for the heart and arteries. Research suggests that copper deficiency is one factor leading to an increased risk of developing coronary heart disease.
A well balanced diet will provide the working body with all of its essential trace elements.
Too much or too little?
Large amounts of essential elements can prove toxic:
- Too much copper in the diet can result in damage to the liver, discolouration of the skin and hair, and can cause hyperactivity in children.
- Too much iron in the diet can result in damage to the heart and liver.
Too little of any given essential element can result in ill health and, if left untreated, could result in death:
- Zinc is a component of certain digestive enzymes and other proteins. Not enough in the diet can result in growth failure, scaly skin inflammation, reproductive failure and impaired immunity.
- People who suffer from iron deficiency show symptoms such as lack of energy, getting tired easily and being short of breath.
Nature of science
Scientific knowledge is never absolute or certain. As scientists discover more about essential elements needed in the diet, old beliefs may have to change in light of new evidence.
Carbon is more than just another element – as explained in the article Carbon – life’s framework element.
The article Periodic table of elements provides a short introduction to elements.
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The comprehensive article All About Oxygen explores oxygen characteristics, biological roles and processes, uses in industry and medicine, and even a brief account of its history.