The correct answer is (1) Peptide Hormones.
Insulin is a peptide hormone that plays a central role in the regulation of blood glucose levels. Here's a detailed explanation:
1. Nature of Insulin:
Insulin is a protein hormone composed of two polypeptide chains. It is produced and secreted by the beta cells of the pancreas, specifically in the islets of Langerhans.
2. Structure of Insulin:
Insulin consists of two peptide chains, namely the A chain and the B chain, linked by disulfide bridges.
The A chain contains 21 amino acids, and the B chain contains 30 amino acids.
The disulfide linkages help maintain the three-dimensional structure of insulin.
3. Synthesis and Secretion:
Insulin is synthesized as a precursor molecule called proinsulin.
Proinsulin undergoes post-translational modification in the endoplasmic reticulum and Golgi apparatus of the beta cells.
The mature insulin is stored in secretory granules in the beta cells until it is needed.
4. Release in Response to Glucose:
The secretion of insulin is tightly regulated by blood glucose levels. When blood glucose levels rise, such as after a meal, beta cells are stimulated to release insulin.
Insulin facilitates the uptake of glucose by cells, particularly muscle and adipose (fat) cells.
5. Functions of Insulin:
Glucose Uptake: Insulin promotes the uptake of glucose by cells by facilitating the movement of glucose transporters to the cell membrane.
Glycogen Synthesis: Insulin stimulates the storage of excess glucose as glycogen in the liver and muscles.
Protein Synthesis: Insulin enhances protein synthesis and inhibits protein breakdown.
Lipid Synthesis: Insulin promotes the synthesis of lipids and inhibits lipolysis, the breakdown of fats.
6. Blood Glucose Regulation:
Insulin works in opposition to another hormone called glucagon, which is also produced by the pancreas. Glucagon raises blood glucose levels, while insulin lowers them.
Together, insulin and glucagon help maintain blood glucose homeostasis.
7. Role in Diabetes:
Diabetes mellitus is a condition characterized by impaired insulin function or insufficient insulin production.
In Type 1 diabetes, the body does not produce insulin, while in Type 2 diabetes, there is either insufficient insulin or the body's cells become resistant to its effects.
In summary, insulin is a peptide hormone crucial for the regulation of glucose metabolism. It facilitates the uptake of glucose by cells, promotes glycogen storage, and has various other metabolic effects. Dysregulation of insulin function can lead to conditions like diabetes. |
