Receptor

A receptor is a protein molecule which causes a change in the cell in response to extracellular signals, via the action of intracellular signalling proteins on a target protein. For example, the electrical activity of a cell changing. They can be found on the cell surface (transmembrane spanning), for example the insulin receptor, or in the cytoplasm (intracellular), for example steroid hormone receptors^[1].

References

1. ↑ Alberts B.(2002),Microbiology of the cell,4th Edition United States,Garland Science, pg 831