Activation of a Receptor by a Chemical Messenger

Multiple Choice

Activation of a receptor by a chemical messenger

A) Occurs when the messenger binds to the ligand-binding site of the receptor
B) Is the first step leading to the ultimate response of a cell to the messenger
C) Requires a change in receptor conformation
D) Both occurs when the messenger binds to the ligand-binding site of the receptor and is the first step leading to the ultimate response of a cell to the messenger are correct
E) All of the choices are correct