are cell-surface receptors with intracellular domains that are associated with an enzyme.
Source: Boundless. “Types of Receptors.” Boundless Biology. Boundless, 21 Jul. 2015. Retrieved 07 Nov. 2015 from https://www.boundless.com/biology/textbooks/1514/cell-communication-9/signaling-molecules-and-cellular-receptors-83/types-of-receptors-381-11607/