Can you explain the different types of protein structure? (primary, secondary, tertiary and quaternary)

The primary structure of a protein is the sequence of amino acids found in the polypeptide chains, this sequence determines the shape and properties of the protein.The secondary structure of a protein is the shape which the polypeptide chain forms due to hydrogen bonding, these can be alpha-helix or beta-sheet (other shapes are possible but these are the most common - the ones you need to know!).The tertiary structure of the protein is due to the bonding and twisting of the polypeptide into a compact structure. There are 3 types of bond: disulphide, ionic and hydrogen bonds. All 3 contribute to the shape and maintenance of shape of the protein, ie if these bonds are broken the tertiary shape is altered. Quarternary structure is when multiple protein chains become linked together to form a complex molecule. There may also be non-protein groups associated with the molecule, for example the iron containing haem group in haemoglobin.