G Protein-Coupled Receptors (GPCRs) are a large family of proteins found in the cell membrane. They play a crucial role in transmitting signals from outside the cell to the inside, helping cells respond to various stimuli, such as hormones, neurotransmitters, and environmental changes. GPCRs are involved in many physiological processes, including vision, taste, and immune responses. When a molecule, known as a ligand, binds to a GPCR, it activates a G protein inside the cell. This activation triggers a cascade of biochemical events, leading to a specific cellular response. GPCRs are important drug targets, as they are involved in numerous diseases, making them key players in pharmacology and medicine.