This rather large protein is insulin. It is clearly a very complicated protein and contains over 150 carbon atoms. As one can imagine, it must be very difficult to synthesise, especially in pre-Dorothy Crowfoot Hodgkin (see Helen Bolger's website) times, as she was the one who managed to deduce its structure using crystallography  on August 14th, 1969. 

    Because syntheses of insulin only produce very low yields, insulin to treat diabetics had, until recently, to be extracted from pigs and other slaughtered animals. Recently, however, researchers have discovered a way to produce large amounts of human insulin by genetic-engineering methods. The process involves generating human insulin using huge vats of bacteria carrying the human insulin gene.

    Insulin is the protein in the body that helps glucose diffuse into the cells. In diabetics, insulin is not readily available from the body so glucose begins to build up inside the bloodstream. If too much glucose is present, the diabetic becomes hyperglycaemic and will feel extremely tired. The more dangerous condition is, however, when too MUCH insulin is present in the body. When this occurs the diabetic is described as being hypoglycaemic. The patient will be in danger of going into a coma and even dying. This is why, if one sees a diabetic faint, it is not necessarily true that they need insulin. It is more likely that they are having a "hypo" and need sugar to increase their BG.