Receptors that are embedded on the cell membrane bind to chemicals outside of the cell and this binding process cause a chemical response on the inside of the cell.
These receptors that help in communication between the cell and the outside world are called cell surface receptors or sometimes transmembrane receptors.
A majority of chemical signals are water soluble thus unable to cross the fatty lipid bi-layer of the cell membrane. Their receptors, which are protein in nature therefore must span the membrane, detect their presence outside of the cell and transmit this information into the interior of the cell.
