How many amino acids are present in insulin?

51

The correct answer is option 2. 51.

Insulin is a peptide hormone produced by the beta cells of the pancreas. It plays a critical role in regulating blood glucose levels by facilitating the uptake of glucose into cells for energy production and storage.

Insulin is composed of two polypeptide chains, known as the A chain and the B chain, which are connected by disulfide bonds. The A chain consists of 21 amino acids. It has one internal disulfide bond (between cysteine residues within the A chain). The B chain consists of 30 amino acids. There are two interchain disulfide bonds that connect the A and B chains. These disulfide bonds are formed between cysteine residues on each chain: One bond between the 7th cysteine on the A chain and the 7th cysteine on the B chain. Another bond between the 20th cysteine on the A chain and the 19th cysteine on the B chain. The presence of these disulfide bonds is crucial for the stability and function of insulin.

Amino Acid Composition

A Chain: 21 amino acids

B Chain: 30 amino acids

Total: 21 + 30 = 51 amino acids

Function of Insulin

Insulin regulates blood glucose levels by promoting the uptake of glucose into liver, muscle, and fat cells, where it is used for energy or stored as glycogen. Here’s a detailed look at its functions:

1. Glucose Uptake: Insulin facilitates the entry of glucose into cells by increasing the number of glucose transporters on the cell membrane.

2. Glycogen Synthesis: In the liver and muscle cells, insulin promotes the conversion of glucose to glycogen for storage.

3. Fat Storage: Insulin enhances the storage of fat in adipose tissue by promoting the synthesis of fatty acids and inhibiting the breakdown of fat.

4. Protein Synthesis: Insulin stimulates the uptake of amino acids into cells, promoting protein synthesis and inhibiting protein degradation.

Synthesis and Release of Insulin

1. Synthesis: Insulin is initially synthesized as a single polypeptide called preproinsulin. This precursor undergoes cleavage to form proinsulin, which further undergoes processing to generate the mature insulin molecule and C-peptide.

2. Release: Insulin is stored in secretory granules in the beta cells and released into the bloodstream in response to elevated blood glucose levels.

Clinical Significance

Diabetes Mellitus: A condition characterized by insufficient insulin production (Type 1 Diabetes) or insulin resistance (Type 2 Diabetes), leading to elevated blood glucose levels.

Insulin Therapy: Used to manage diabetes by providing exogenous insulin to mimic the normal physiological insulin response.

Insulin is a hormone composed of 51 amino acids in total, arranged into two chains: the A chain with 21 amino acids and the B chain with 30 amino acids. These chains are connected by disulfide bonds, crucial for the hormone's stability and function. Insulin plays a vital role in regulating glucose metabolism, promoting glucose uptake, and ensuring proper energy storage and utilization in the body.