Which ONE of the following best describes differences between the RTK signal transduction pathway and the GPCR signal transduction pathway?
A. The GPCR pathway is deactivated via hydrolysis, while the RTK pathway is deactivated by phosphatases.
B. The GPCR pathway requires phosphorylation of critical tyrosine residues, while the RTK pathway requires GDP/GTP exchange.
C. The GPCR acts as both the receptor and the enzyme, while the RTK system has separate receptor and enzymatic proteins.
D. The GPCR pathway involves the binding of extracellular ligands, while the RTK pathway involves the binding of intracellular ligands