Question

Most of the peptide hormones and neurotransmitters are synthesized in advance and stored for later release, whereas paracrine peptides such as ________ are synthesized only on demand.

Answer 1

Paracrine peptides such as substance P are synthesized on demand and function at the local level, unlike peptide hormones like insulin that are stored for later use.

Step-by-step explanation:

Paracrine peptides, unlike peptide hormones like insulin which are stored in vesicles, are synthesized on demand. Peptide hormones typically consist of short to long chains of amino acids, and they are insoluble in lipids, which means they cannot pass through the plasma membrane and thus require exterior cell receptors for their function.

An example of a paracrine peptide is substance P, which along with other neuropeptides like vasoactive intestinal peptide (VIP), functions at the local level and is produced only when needed.