Insulin

Source of secretion:

Insulin is secreted by Beta cells in islets of Langerhans of pancreas.

Chemistry/structure:

Insulin is a polypeptide with molecular weight of 5808. It has two amino acid chains linked by disulfide bonds. Alpha chain of insulin contains 21 amino acids and beta chain contains 30 amino acids.

Synthesis:

Initially, it is synthesized as prepro insulin. Later this prepro insulin undergoes proteolytic cleavage to give rise to insulin and C peptide.

Metabolic Roles:

Insulin is known as hypoglycemic hormone. The main role of insulin is to decrease blood sugar level by participating in various metabolisms.

1. Effect on carbohydrate metabolism:

• Insulin helps in activating glucose transporter 4(GLUT 4). This glucose transporter helps in taking glucose from blood to the tissues.
• Insulin helps in utilization of glucose by peripheral tissues.
• Insulin promotes rapid conversion of glucose into glycogen (glycogenesis). The glycogen is the storage form of carbohydrate in animals.
• Insulin inhibits the glycogenolysis (conversion of glycogen to glucose).
• Insulin inhibits gluconeogenesis (formation of glucose from non carbohydrate source).

2. Effect on protein metabolism:

• Insulin helps in synthesizing proteins and inhibits the cellular utilization of proteins.
• Insulin decreases the catabolism of proteins and inhibits gluconeogenesis.

3. Effect on fat metabolism:

• Insulin causes synthesis of fat.
• Insulin promotes storage of fats in adipose tissues.

4. Effect on growth:

• Along with growth hormone insulin promotes growth of the body.