Hormone Mechanisms: Receptors, Signaling, and Second Messengers

Notes

Distant target cells CRITICAL CONCEPT: All hormones have 1 or more types of target cells. To be a target cell for a hormone, all a cell must do is have a receptor for that hormone. General Mechanisms of Action for Hormones • Hormones bind to cell surface receptors or receptors inside target cell • Cell responds via: – synthesis of new molecules – change in membrane permeability – altered rates of reaction • Different target cells may respond to the same hormone differently. – Hepatocytes - insulin stimulates glycogen synthesis – Adipocytes - insulin stimulates triglyceride synthesis Steroid Hormone Action Free hormone Transport protein Blood capillary 1 • Receptors are typically intracellular. • Work by changing the level of specific gene expression 2 Lipid-soluble hormone diffuses into cell Activated receptor–hormone complex alters gene expression Cytosol 3 Newly formed mRNA directs synthesis of specific proteins on ribosomes Plasmalemma Nucleus Receptor 4 DNA mRNA Ribosome New protein New proteins alter cell's activity NOTE: The response by target cells to steroid hormones is relatively slow! Target cell Peptide Hormone Action • Peptide hormones bind to cell surface receptors • P...