Ligand gated ion channels/receptors are large multisubunit complexes which are usually pentamers (5 subunits) that form an ion channel in the membrane. The complex may be heteromeric in that it is composed of several different types of subunits or homomeric in that it is composed of a single type of subunit. Each subunit of the complex contains 4 hydrophobic transmembrane domains. The amino and carboxyl termini are each on the cytosolic side of the membrane.

It typically takes 2 molecules of ligand bound to open an ion channel. The ligand binding site is about 1/3 down the way in the channel. The response to this binding is rapid (millisec) enabling ions to flow down their electrochemical gradients. Ligand gated ion channels typically contain allosteric binding sites.