Which molecule in this figure portraying water- soluble hormone action is the receptor protein?

Question

Quizplus · Accepted Answer

Molecule B is the receptor protein, as it is the protein that binds to the water-soluble hormone (molecule A) and initiates the signal transduction pathway by interacting with molecule C (a G protein). Molecules C and D are both involved in the signal transduction pathway, but they are not the receptor protein.

Which Molecule in This Figure Portraying Water- Soluble Hormone Action