Peptide hormones

Definition

Peptide hormones are signaling molecules composed of amino acid chains that regulate physiological functions. They are synthesized in endocrine glands and act on specific target cells to elicit responses.

5 Must Know Facts For Your Next Test

1. Peptide hormones are water-soluble, allowing them to travel freely in the bloodstream.
2. They bind to receptors on the surface of target cells because they cannot cross the lipid bilayer of cell membranes.
3. Examples include insulin, glucagon, and antidiuretic hormone (ADH).
4. Peptide hormones often initiate a signal transduction pathway involving second messengers like cAMP.
5. Their effects are typically rapid but short-lived compared to steroid hormones.

Review Questions

• Why do peptide hormones bind to surface receptors instead of entering the cell?
• Name three examples of peptide hormones.
• How do peptide hormones initiate cellular responses?

Related terms

Steroid Hormones: Lipid-soluble molecules derived from cholesterol that can pass through cell membranes and bind to intracellular receptors.

Signal Transduction Pathway: A series of molecular events triggered by an extracellular signal binding to a receptor, leading to a cellular response.

Second Messenger: Small intracellular molecules like cAMP that propagate signals from receptors to target molecules inside the cell.