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BIOL 3090 (2)
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Chapter 15

CHAPTER 15 Notes (got 93% on the test)

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Louisiana State University
Biological Sciences
BIOL 3090

CHAPTER 15Signaling at the Cell SurfaceSignal transductionoverall process of converting extracellular signals into intracellular responsesSignaling moleculeligandoBinds to a structurally complementary protein on the extracellular domain called a receptorResponses vary but generally includeoCellular metabolism oCell division cancera lose in this regulationoCell differentiationoCell morphology or mobilityTypes of SignalingEndocrine Signaling release of a molecule into the bloodstream to distant target cellsoEx Pancreas cells secreting insulin FIG 152aoHormone signaling molecule that mediates endocrine signalingParacrine Signaling only affects cells in close proximity SHORT distance oEx A neuron secreting a neurotransmitter FIG 152boDiffusion only can go so farshort distanceAutocrine Signaling secreted growth factors act on the same celloCancer cells often use autocrine signaling FIG 152cLigandA small signaling molecule or proteinBinds to a receptor on the cell surfaceReceptor changes its conformation to initiate cell responseDifferent receptors determine how well a cell responds to external signalsDifferent receptors for the same ligand could initiate different responsesSame receptor in different cells may cause different responses depending on the cell typeEx AcetylcholineoCauses striated muscles to contractoCauses smooth and heart muscle to slow its rate of contractionoCauses pancreatic acinar cells to rapidly secrete enzymesA particular cell response could be triggered by different ligands and receptorsoEpinephrine and glucagon both cause glycogenbreakdown in liver cellsoBoth increase production of cAMP in the cytoplasmcAMP then serves as a second messengerOnly apparent function of the ligands is to bind receptorsoTo initiate signal transductionoSome ligands are degraded after binding their receptorsDimerizationBinding specificityby the receptor only one kind of ligand can bind FIG 153bEffector specificityreceptorligand complex initiates a particular cellular responseOnce ligand binds the gray receptor a second blue receptor could bind to form a receptor dimer FIG 153cHormones as LigandsLipophilic hormonesoDiffuse through the plasma membraneoBind intracellular cytosolic receptorsoReceptorhormone complex then acts as a transcription factoroLipophilic hormones that can bind cytosolic receptorsSteroids
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