• Has a very important role in humans
• Proteins are made up of amino acids – peptide bonds is what holds the amino acids together in the protein
• An amino acid is made up of an amine group, carboxyl group and an R group. It is this R group that varies between the 20 common amino acids. (See diagram)

(Image from: CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=199725)

Main roles of proteins:

• Catalysing reactions – enzymes (see discussion below)
• Transportation of molecules – channels that are embedded in the plasma membrane
• Cell signalling – insulin is a protein that binds to insulin receptors that will trigger a response by the human body to take up the excess glucose that is floating around in the blood.
• Structure – keratin is a type of protein that makes up our hair and nails.
• Immunology – antibodies that are made by the B-cells are proteins that help to destroy any foreign material within our bodies.