Final answer:
Receptor tyrosine kinases are enzyme-linked receptors that are activated by ligand binding and dimerization, leading to autophosphorylation and initiation of cellular responses. Their activity is terminated by phosphatases.
Step-by-step explanation:
The receptor tyrosine kinase superfamily refers to a class of enzyme-linked receptors that have intrinsic enzyme activity, specifically a tyrosine kinase. These receptors are characterized by a single transmembrane region and distinct extracellular and intracellular domains. When a signaling molecule binds to the receptor's extracellular domain, it causes two receptors to dimerize (bind together). This leads to the autophosphorylation of tyrosine residues within the intracellular domain, which initiates a cascade of cellular responses. The phosphorylated tyrosine residues act as docking sites for downstream signaling proteins, propagating the signal within the cell. The response is terminated by the action of phosphatases, which remove the phosphate groups from the tyrosine residues, thus inactivating the receptor.