a cell or group of cells that receives stimuli which are then transmitted as nerve impulses, e.g. a esp a nerve ending, e.g. in the skin, or sense organ, e.g. a taste bud, that receives information about temperature, light, sound, etc from the environment
a chemical group on the surface of a cell that provides a site for a particular antibody or a virus to attach to
a chemical structure, e.g. on an enzyme, that provides a site of attachment
a chemical structure in or on the surface of a cell, to which a hormone, neurotransmitter, etc binds, triggering off a reaction, e.g. transmission of a nerve impulse, inside the cell