Cyclic AMP functions as a second messenger to:
(a) Build proteins and catalyze specific reactions
(b) Activate adenylate cyclase
(c) Open ion channels and activate key enzymes in the cytoplasm
(d) Bind the hormone–receptor complex to DNA segments

Cyclic AMP (cAMP) is a crucial second messenger in cellular signaling pathways. It is synthesized from ATP by the enzyme adenylate cyclase in response to various hormones and signals. cAMP transmits signals from cell surface receptors to target proteins within the cell, thereby influencing various physiological processes such as metabolism, gene expression, and cell growth.

A second messenger system refers to the intracellular signaling mechanisms that relay signals from receptors on the cell surface to target molecules inside the cell. These systems amplify the strength of the signal and can lead to a variety of cellular responses, such as changes in enzyme activity, ion channel permeability, or gene expression. cAMP is one of the most well-known second messengers, playing a pivotal role in mediating the effects of hormones like adrenaline.

Adenylate cyclase is an enzyme that catalyzes the conversion of ATP to cyclic AMP (cAMP) and pyrophosphate. It is activated by G-proteins that are linked to cell surface receptors. The activation of adenylate cyclase is a key step in the signaling pathways of many hormones, leading to increased levels of cAMP, which then activates various downstream effectors, including protein kinases and ion channels.