Receptors

Receptors are vital to cell communication in various different forms of signalling - paracrine, synaptic, endocrine etc. They are proteins that bind specific signal molecules to trigger a response from the target cell. Receptors can be transmembrane proteins found on the extracellular surface of target cells, or they can be found inside the cell. In the case of intra-cellular receptors the signalling molecule must enter the cell to activate the receptor .