Describe the structure of globular proteins.

There are 4 levels of structure associated with a globular protein; primary, secondary, tertiary and quarternary. The primary structure is the organisation of amino acids, bonded by peptide bonds. The secondary structure is the shape this chain of amino acids takes and can be either a Beta pleated sheet or a Alpha helix. The secondary structure is determined by hydrogen bonding between carbonyl groups and the amino H of each amino acid. The tertiary structure is determined by the folding of an alpha helix or beta pleated sheet. This folding is caused by interactions between R groups of amino acids which include ionic bonding, hydrogen bonding, dipole-dipole interactions, hydrophobic interactions and disulphide bridges. The final level is quarterary which is the arrangement of multiple polypeptide chains held together by hydrogen bonding, disulphide bridges and London forces.