Question

In the mechanism of action of protein hormones, one of the second messengers is

• A. Cyclic AMP
• B. Insulin
• C. Gastrin
• D. Inositol triphosphate

Answer 1

Answer: (A), (D)

The correct options are
A Cyclic AMP
D Inositol triphosphate

Hydrophilic hormones do not enter the cell but such hormones have receptors present externally, nestled in their cell membrane called cell surface or plasma membrane receptors. So these hormones attach to their respective receptors. This causes a cascade of steps that result in the production of molecules called second messengers inside the cells. In one type of pathway, the second messenger is a substance called cAMP, produced by enzymatic action on ATP. Another type of pathway, called the phosphatidylinositol/ calcium pathway involves enzymatic reaction on cell membrane lipids releasing inositol triphosphate and another substance. This leads to calcium release within the cell. Calcium and IP3 together act as second messengers. The job of second messengers is to convey the message from hormones or primary messengers to inside of the cell.