Final answer:
A-kinase, also known as protein kinase A (PKA) or cAMP-dependent kinase, is an enzyme that is activated by cAMP. It regulates metabolic pathways by phosphorylating target proteins, activating them. A-kinase is found in different types of cells, leading to varying responses to cAMP.
Step-by-step explanation:
A-kinase, also known as protein kinase A (PKA) or cAMP-dependent kinase, is an enzyme that is activated by binding to cyclic AMP (cAMP) as a second messenger molecule. It plays a vital role in regulating metabolic pathways by phosphorylating specific target proteins, thereby activating them. A-kinase is found in different types of cells, and its target proteins vary among these cells, resulting in different responses to cAMP.