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Science

Biological compounds

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The biosphere refers to all living organisms, both plants and animals, on Earth.

Compounds in living organisms

Living things are mainly made from compounds that contain the elements carbon, hydrogen, oxygen and nitrogen. There are smaller amounts of other elements such as phosphorus and sulfur. There are also traces of most of the other elements.

Amino acids and proteins

Proteins are polymers. They are built up by the joining together of monomers called amino acids. There are only 20 different amino acids, but each protein molecule has hundreds, or even thousands, of them joined together in a unique sequence. This gives each protein its own individual properties. The proteins in hair, skin and muscle each have properties suited to their function.

The diagrams show two of these amino acids:

glycinealanine

Carbohydrates

Carbohydrates have the empirical formula CH2O. This means that each carbohydrate has twice as many hydrogen atoms as carbon or oxygen atoms.

The simplest carbohydrates are sugars such as glucose. These sugar molecules can polymerise to make giant carbohydrate molecules such as starch and cellulose.

Glucose has the molecular formula C6H12O6.

The structure of a glucose molecule is shown in the diagram below:

The structure of glucose

Fats

Fats are also compounds of carbon, hydrogen and oxygen. They are esters of fatty acids and glycerol.

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Back to Chemicals of the natural environment index

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