What do the hormones that bind to cell surface receptors do?

Answer:
Lock and Key to the Nth Degree. When any one of 'very many' intercellular 'blood borne' Activating Factors finds & fits-to a Cell Surface Receptor, this causes conformational changes to the 'Transmembrane Signal Proteins' that rapidly become apparent on the cytoplasmic 'side' of the cell membrane as another signal or set of signals, usually directed to the Nucleus.
First answer by Betaclamp. Last edit by Betaclamp. Contributor trust: 106 [recommend contributor recommended]. Question popularity: 1 [recommend question].