Receptor Proteins

Receptors are proteins molecules located on the cell surface or within the cytoplasm that function by specifically recognizing and binding to a ligand molecule. The ligands are the signaling molecules released by one cell to signal either itself or a different cell. The major types of cellular signaling include autocrine, signal across a gap junction, paracrine, and endocrine. These types of signaling require ligand and receptor. Cellular receptors are diverse and broadly categorized into internal receptors, cell-surface receptors, ion channel receptors, G-protein-coupled receptors (GPCRs), and enzyme-linked receptors.