Question

Which of these is a 32 amino acid water soluble peptide hormone?
a. Gastrin
b. Insulin
c. Glucagon
d. Calcitonin

Answer 1

Hint: Hormones are the chemical messengers that are directly secreted into the blood. Water-soluble peptide hormones include: follicle-stimulating hormones, thyroid stimulating hormones, luteinizing hormones and insulin.

Complete answer:
Gastrin is a peptide hormone that plays an important role in the secretion of HCl by the parietal cells of the stomach. It also plays a role in gastric motility, mucosal growth. This hormone is produced by the ‘G’ cells of the stomach lining and the duodenum. It is composed of 101 amino acid residues giving it a molecular mass of 11.4 kDa.

Insulin is a peptide hormone that is produced by the beta-cells of pancreas. The role of insulin is to control the blood glucose levels by giving signals to liver, muscles and fat cells to take in glucose from the blood, thereby reducing blood sugar level.. Insulin hormone is composed of two peptide chains i.e., A and B chains. A-chain consists of 21 amino acids and B-chain is made up of 30 amino acids. Its molecular weight is about 5.8 kDa.

Glucagon is a peptide hormone that is produced by alpha-cells of pancreas. This hormone is known to raise the concentration of glucose and fatty acids in the bloodstream. It is made up of 29 amino acid residues and has a molecular weight of about 3.5 kDa.

Calcitonin hormone is produced in the thyroid glands by its parafollicular cells (commonly known as C-cells of thyroid glands). It is known for regulating the levels of calcium and phosphate in the blood. It lowers the calcium levels, an action that is opposed to that of parathyroid hormone. This hormone is made of 32 amino acid residues and has a molecular weight of about 3.45 kDa.

Hence, the correct answer is option (D).

Note: Calcitonin which is a water soluble peptide hormone is made up of 32 amino acid residues. It is produced by the C-cells of thyroid glands. It plays a role in lowering the calcium levels in blood.