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30 - Desensitization Epinephrine receptor—continuous...

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30.1 Signal Transduction Purpose—regulate cellular responses to extracellular signals Single cell organisms respond to food mostly Glucose Starvation Chemotaxis Multicellular organisms: cells must communicate with each other
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30.2 Cells communicate in different ways Receptor types: Steroid hormone receptors Heterotrimeric G-protein coupled receptors Tyrosine kinase receptors
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30.3
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Heterotrimeric G protein coupled receptors Include receptors for epinephrine, prostaglandins ~1000 different receptors in this family in humans In the absence of hormone, heterotrimeric G protein binds GDP (inactive) Hormone receptor complex stimulates exchange for GTP Activates target (adenylate cyclase here) (signal amplification) GTP slowly hydrolyzed to GDP (molecular clock) limits response Inhibitory G proteins too that work with different receptors (integration of response to multiple hormones) 30.4 Receptor (serpentine receptor) 7 transmembrane helices
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