AP BIOLOGY

Detailed explanation-1: -Top: In general, receptor tyrosine kinases (RTKs) associate into dimers when ligand (red) binds to their extracellular regions.

Detailed explanation-2: -Receptor tyrosine kinases (RTKs) are a group of membrane-bound receptors that play an important role in the normal function of cells. They act as signal transducers that mediate cell-to-cell communication by phosphorylating tyrosine residues on key intracellular substrate proteins.

Detailed explanation-3: -The transmembrane (TM) domains of receptor tyrosine kinases (RTKs) play an active role in signaling. They contribute to the stability of full-length receptor dimers and to maintaining a signaling-competent dimeric receptor conformation.

Detailed explanation-4: -RTKs are all synthesized as single-pass transmembrane proteins and bind polypeptide ligands, mainly growth factors. It has long been thought that all RTKs, except for the insulin receptor (IR) family, are activated by ligand-induced dimerization of the receptors.

Detailed explanation-5: -Receptor tyrosine kinases are part of the larger family of protein tyrosine kinases, encompassing the receptor tyrosine kinase proteins which contain a transmembrane domain, as well as the non-receptor tyrosine kinases which do not possess transmembrane domains.