Receptors are specialized proteins that bind to specific ligands, which can be endogenous molecules like hormones and neurotransmitters, or exogenous substances such as drugs and environmental chemicals. Upon binding to their ligands, receptors undergo conformational changes that trigger a cascade of intracellular events, ultimately leading to a biological response. There are several types of receptors, including G protein-coupled receptors (GPCRs), ion channel receptors, and nuclear receptors.
