Question

Hormones are called chemical signals that stimulate specific target tissues. Their action depends on the presence of receptors on the respective target tissues. Which of the following is the correct location of the receptors in the case of protein hormones?

• A. Extracellular matrix
• B. Plasma membrane
• C. Blood
• D. Nucleus

Answer 1

The correct option is B Plasma membrane

Hormones and their chemical nature :

Hormones are the non-nutrient chemicals produced in trace amounts acting as intercellular messengers. Based on solubilities, they are of two major types:

• Lipid soluble hormones: Steroid hormones
• Water soluble hormones: Protein hormones, amino acid derived hormones etc.

Mechanism of action:

Hormones function by binding to their receptors which are located on the target site, to form the hormone receptor complex. The receptors are usually located either on the plasma membrane (membrane receptors) of the targets or inside the cell as in nucleus (intracellular receptors).

• Water soluble hormones bind to membrane receptor complexes. This binding generates other molecules like Ca++, cAMP etc. which act as secondary messengers. These secondary messengers drive biochemical and physiological changes in the cell.
• Lipid soluble hormones enter the cell by crossing the plasma membrane and bind to intracellular receptors to form hormone-receptor complex.

Protein hormones :

Protein hormones are water-soluble and cannot directly cross the plasma membrane. Therefore, their receptors are located on the surface of the plasma membrane so as to form hormone-receptor complexes and drive the subsequent biochemical pathway.

Final answer:

c. Plasma membrane