Glucagon is a hormone found within the alpha cells of the islets of Langerhans in the pancreas in Homo sapiens. Its primary function is to raise blood glucose levels in order to prevent Hypoglycaemia and maitain a constant internal environment. The hormone achieves this through the conversion of stored glycogen to glucose. Glucose can then be secreted into the blood stream which raises blood glucose levels. Glucagon is used in conjunction with insulin, together they are used to regulate the blood glucose levels.
Glucagon is a type of peptide hormone with 29 amino acids in a linear structure. Glucagon is produced originally as a formation of proglucagon in the pancreas, which is then converted to glucagon as a functional state in alpha cells of the islets .
The primary role of glucagon played in the body is increasing the blood glucose concentrations, which is the opposite function of insulin, secreted from beta cells of the islets. To be specific, glucagon raises the blood sugar levels through the breakdown of the glycogen in the liver when the concentration of the blood glucose is low . This process is called glycogenolysis, which is decomposition of glycogen into glucose . Another function of glucagon is activating gluconeogenesis, which convert non-hexose, for instance, amino acids, to glucose also for increasing the blood sugar levels 
- ↑ 1.0 1.1 1.2 R.Bowen (1999), Glucagon, http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/glucagon.html (last accessed 09.01.11)
- ↑ 2.0 2.1 Berg J., Tymoczko J. and Stryer L. (2007) Biochemistry, 6th edition, New York: WH Freeman(p601-603).