Cells grown in the laboratory are mixed with a charged dye molecule that is unable to pass through the plasma membrane. If a ligand is added to the cells, the dye is observed entering the cells. What type of receptor did the ligand bind to on the cell surface

ion channel receptor

Explanation:

Ion channel receptors appear to be multimeric proteins in the plasma membrane. Growing of these proteins organise itself to form a pore or passage which extends from one side of the membrane to the other.

when the ligand is added to the cells, ion channel receptors allows the dye to enter into the cell.