Receptor
(Latin = recipient)
Receptors are proteins which are located on the outer membrane of a cell or within a cell and which function as a “docking station” for messenger substances.
When the messenger attaches to one of these docking stations, the protein becomes deformed and thus activates a molecular switch inside the cell. This switch turns on specific operating programs.
This is how the information of the messenger is transmitted to a specific signaling system of the cell.