A class of nitrogen-containing molecules containing an amine group, a carboxylic acid group and a side chain that varies between different amino acids. Amino acids are the building blocks from which protein is made in the body.
There are 20 known standard amino acids forming various proteins. When taken up into the body in the diet, the 20 standard amino acids are either used to synthesise proteins and other biomolecules or broken down into urea and carbon dioxide.
Of the 20 standard amino acids, eight are called essential amino acids and the other 12 are called non-essential amino acids. Animals (including humans) cannot synthesise the essential amino acids from other compounds at the level needed for normal growth, so they must be obtained from food (hence they are called essential amino acids).« Back to Glossary Index