The number and order of amino acids in the chain is specific for each protein.
For example the protein insulin, which helps cells take in glucose, has a small chain of 51 amino acids in an order that no other protein has.
Haemoglobin is a much larger, complex protein found in red blood cells. It carries oxygen and is made of four linked chains, two of which have 141 amino acids and two have 146 amino acids.
The order of the amino acids causes the chain to fold up in a particular way and gives the protein a specific 3D shape.
Some proteins such as keratin found in human hair and nails, form long, strong fibrous molecules. Other proteins such as insulin, haemoglobin and enzymes, have a round 'globular'…