Question

What is a Second Messanger?

Explain types of second messengers?

1. Ionotropic

2. Metabotropic

3. Vesicular

4. Transporters

Answer 1

Second messengers are intracellular signaling molecules which are released by the cells to trigger physiological changes. These changes include proliferation, differentiation, migration, survival, and apoptosis. They are also considered one of the initiating components of intracellular signal transduction cascades.

Examples: cyclic AMP, cyclic GMP, inositol trisphosphate, diacylglycerol, and calcium.

Types: There are three basic types of secondary messenger molecules:

• Hydrophobic molecules: water-insoluble molecules such as diacylglycerol, and phosphatidylinositols
• Hydrophilic molecules: water-soluble molecules, such as cAMP, cGMP, IP₃, and Ca²⁺, that are located within the cytosol.
• Gases: nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S) which can diffuse both through cytosol and across cellular membranes.