Receptor: A receptor is a specialized protein molecule located on the cell surface that recognizes specific molecules (ligands) and triggers cellular responses.
Adenylyl cyclase: Adenylyl cyclase is an enzyme responsible for converting ATP into cyclic AMP (cAMP), which serves as a secondary messenger in many cellular signaling pathways.
Second messenger: Second messengers are small molecules or ions generated within cells in response to extracellular signals. They relay signals from receptors on the cell surface to target molecules inside the cell, amplifying and diversifying the original signal.