Final answer:
Cyclic AMP concentration rises rapidly through a signaling pathway involving multiple steps in response to an extracellular signal.
Step-by-step explanation:
In response to an extracellular signal, cyclic AMP (cAMP) concentration rises rapidly through a signaling pathway involving several steps.
1. An extracellular chemical signal binds to its receptor on the cell membrane.
2. The receptor activates a G protein, which in turn activates the enzyme adenylate cyclase.
3. Adenylate cyclase converts ATP to cAMP.
4. cAMP serves as a second messenger and activates protein kinase A (PKA), initiating a phosphorylation cascade.
5. PKA phosphorylates and activates various target proteins, leading to the cellular response.
Overall, this pathway allows for amplification and specificity in the cellular response to the extracellular signal.