Describe the primary and secondary structure of proteins

Primary structure:
Due to the bonding and the shape and chemical nature of different amino acids, the shape of a whole chain of amino acids (a polypeptide or protein) is specific. The shape determines the properties of the protein, therefore, the primary structure depends on the order and number of amino acids in a particular protein.
For example: Haemoglobin is made up of 4 polypeptide chains, 2α chains and 2β chains, each with a haem group attached. There are 146 amino acids in each chain. If just one of these is wrong, serious problems can arise (e.g. sickle cell anaemia). The red blood cells become distorted, the amount of oxygen they can carry is reduced and blood capillaries can be blocked, leading to acute pains called crises.
Secondary structure:
This is the basic shape that the chain of amino acids takes on. The 2 most common structures are the α-helix and the β-pleated sheet.
α-helix: This has a regular coiled structure like a spring, with the R groups pointing towards the outside of the helix. Hydrogen (H) bonds are relatively weak but because there are so many, the total binding effect is strong and stable. The helix is flexible and elastic [draw diagram on whiteboard]
β-pleated sheet: This is composed of 'side by side' chains connected by H bonds. All the peptide linkages are involved in inter-chain H bonding so the structure is very stable [draw diagram on whiteboard]