Relatively Small Quantities of Neuropeptides Are Required for Signaling, in Part

Relatively small quantities of neuropeptides are required for signaling, in part because

A) they have a much higher affinity for their receptors than low-molecular-weight transmitters.
B) they are synthesized so quickly that a continuous supply is available.
C) one molecule can typically bind to many receptors at a time.
D) the binding sites are extremely close to the release sites.
E) their metabotropic receptors can amplify the signal through intracellular pathways.