Proteins come in many different forms and have many different functions, for example:
Part of your DNA –  Your genetic inheritance!  Proteins combine with nucleic acids to form nucleoproteins, in the nucleus of every cell in your body.
Enzymes – These are the proteins which make everything happen, e.g. to break down food for absorption.
Haemoglobin – The protein which, with iron, carries oxygen around your body;
Myoglobin and elastin – These are the two main proteins in muscle fibres;
Bones are mainly proteins, with calcium, magnesium and phosphate;
Hormones which send chemical messages between nerve cells and to regulate metabolism;
Antibodies which circulate in your blood to protect you against viruses; and
Keratin which forms your hair and nails.
What exactly is protein?
The order of amino acids in the chain is programmed by DNA.  “Amino” means that they contain nitrogen, but they also contain carbon, hydrogen and oxygen atoms.
There are around 30,000 to 50,000 different proteins in the human body!  Each has its own unique gene in our DNA which arranges the 22 amino acids in a unique sequences.  Proteins in the body cells are continuously being formed and broken down by enzymes, so amino acids are continuously being recycled from broken down proteins as well as the diet.