Types of Cell Surface Receptors

Specific receptors on cell surfaces (and in the
nucleus or cytosol) convey cell-to-cell signals
into the cells and the functional answers. The
basic structures of their genes are similar because
they have been derived from a relatively
small group of ancestral genes. They way they
bind to the ligand (the signal-releasing
molecule) and the functional answer of the cell
are specific. When a ligand binds to a receptor, a
series of reactions is initiated that alters the
function of the cell. Receptors with direct and
indirect ligand effects can be distinguished.