Answer:
The cyclic AMP (cAMP) second messenger system involves a set of events that occurs in response to the binding of a signaling molecule (such as a hormone or neurotransmitter) to its receptor on the surface of a target cell. The sequence of events involved in the cAMP second messenger system can be summarized as follows:
1. A signaling molecule (first messenger) binds to its receptor on the cell surface.
2. The receptor activates a G protein, which in turn activates an enzyme called adenylyl cyclase.
3. Adenylyl cyclase converts ATP to cyclic AMP (cAMP), the second messenger.
4. The cAMP binds to and activates an enzyme called protein kinase A (PKA).
5. Activated PKA phosphorylates (adds a phosphate group to) specific target proteins inside the cell, leading to cellular responses such as the release of stored molecules or the activation/deactivation of certain enzymes.
6. Phosphodiesterases break down the cAMP to terminate the signaling process and reset the system for the next cycle.
This process amplifies the initial signal and allows for a rapid and coordinated response to the initial stimulus.