HORMONES OF PANCREAS AND THEIR ROLE -
(i) Glucagon (Secreted by a-cells)
- It stimulates the liver to convert stored glycogen into glucose.
- Glucagon is controlled by feedback in accordance with the level of glucose in the blood. When the blood sugar rises, the secretion of glucagon is suppressed and when it drops, the secretion of glucagon is stimulated.
Target Cells. Glucagon acts on the cells of the liver and adipose tissue.
(ii) Insulin (Secreted by b-cells)
- It was first prepared / found by Benting and Best.
- A. F. sanger coined the term insulin & proposed the molecular structure of insulin (cow's insuline)
- Human insulin was synthesized by "Tsan".
- Insulin was the first protein that was artificially synthesized in laboratory and is crystallized.
- One molecule of insulin is made up of 51 amino acids that has 2 chains - (i) a-chain. It is made up of 21 aminoacids.
(ii) b-chain. It is made up of 30 amino acids. Both the branches or chains are bind together with cross bonds of disulphide bonds.
(iii) Somatostatin (SS)
It regulates the secretion of insulin and glucagon.
Target Cells. Both somatostatin and pancreatic polypeptide act on the cells of the pancreas.
(iv) Pancreatic Polypeptide (PP).
It appears that pancreatic polypeptide inhibits the release of digestive' secretion of the pancreas.
Both somatostatin and pancreatic polypeptide are relatively newly discovered hormones of the pancreas, and both are still being studied.