Insulin. Molecular ball-and-stick molecule of the hormone insulin, which is essential in maintaining the balance of glucose metabolism in the body. Atoms (spheres) are colour coded: carbon (green), oxygen (red) and hydrogen (blue). Insulin is a protein comprising 51 amino acids. It is produced in the pancreas by cells of the Islets of Langerhans. Insufficient production of insulin can lead to an accumulation of glucose in the blood.