Cyclic AMP (cAMP) plays a crucial role as a secondary messenger in various biological processes. It is involved in the regulation of glycogen, sugar, and lipid metabolism, helping to control energy utilization in cells. In cellular signaling, cAMP activates protein kinase A (PKA), which then phosphorylates specific proteins to trigger a cascade of cellular responses. This mechanism is vital in processes such as hormone action, where cAMP mediates the effects of hormones like adrenaline and glucagon. Additionally, cAMP is significant in the regulation of ion channels and cellular communication in the nervous system, influencing neurotransmitter release and neuronal excitability. It also plays a role in gene expression by modulating transcription factors, thereby affecting cell growth and differentiation. In the immune system, cAMP is involved in regulating inflammatory responses and immune cell activity. Its diverse functions make it a key molecule in maintaining cellular homeostasis and responding to external stimuli.