The receptors for a group of signaling molecules known as growth factors are often Naim 04:56 AP Biology Practice Questions The receptors for a group of signaling molecules known as growth factors are often A) ligand-gated ion channels. B) G-protein-linked receptors. C) cyclic AMP. D) tyrosine kinase receptors. E) neurotransmitters. Answer: D Learn More : Share this Share on FacebookTweet on TwitterPlus on Google+