Proteins are made up of 20 different building blocks, the amino acids.

These building blocks are strung together like pearls on a necklace. Very small proteins are made up of only ten building blocks, whereas very large ones can consist of several thousand amino acids. The amino acids are linked together in various combinations, forming chains of 40 to 400 protein components. Significant are the kind of components and the order in which the components were linked together as each amino acid gives the protein certain characteristics which are important for its functionality. For instance, the shape of the protein depends on the kind and the sequence of the amino acids: some proteins form long, screw-shaped chains, like the protein in our hair. Others have round or twisted shapes, such as the protein in the red blood corpuscles which transports oxygen.

The “blueprint” for the exact sequence of amino acids is specified in the genes.