Histamine is a chemical substance released in inflammatory and allergic responses. the histamine h1 receptor on target cells is a g protein-coupled receptor that activates phospholipase c in response to the binding of histamine. which statements are true about the binding of histamine to the histamine h1 receptor? select all that apply.

a. histamine binds extracellularly to the h1 receptor.
b. when histamine binds to the h1 receptor, the receptor undergoes a conformation change and binds the inactive g protein.
c. once the g protein is active, it binds to the enzyme phospholipase c, activating it.
d. histamine is likely hydrophilic.