Which Statement Is NOT True for G Protein-Coupled Receptors (GPCRs)

Multiple Choice

Which statement is NOT true for G protein-coupled receptors (GPCRs) ?

A) Agonists mimic the effect of the natural ligand.
B) Antagonists block the normal effect of the natural ligand.
C) GPCRs interact with heterodimeric G proteins.
D) GPCRs are have seven transmembrane helices.
E) There exist >100 orphan GPCRs in the human genome with no known ligand.