Proteins are made up of many different amino acids linked together. There are twenty different of these amino acid building blocks commonly found in plants and animals. A typical protein is made up of 300 or more amino acids and the specific number and sequence of amino acids are unique to each protein. Rather like the alphabet, the amino acid 'letters' can be arranged in millions of different ways to create 'words' and an entire protein 'language'. Depending on the number and sequence of amino acids, the resulting protein will fold into a specific shape. This shape is very important as it will determine the protein’s function (e.g. muscle or enzyme). Every species, including humans, has its own characteristic proteins.