2Cell-Cell Communication Animal cells use gap junctions to send signalsCells must be in direct contactProtein channels connecting two adjoining cellsGap junctionsbetween animal cells
3Cell-Cell Communication Plant cells use plasmodesmata to send signalsCells must be in direct contactGaps in the cell wall connecting the two adjoining cells togetherPlasmodesmata between plant cells
4Local Signaling Other types of signaling over a short distance Cell-cell recognitionMembrane bound cell surface moleculesGlycoproteinsGlyolipidsLocal regulatorsGrowth factorsOnly work over a short distance
5Long-Distance Signaling Nervous System in AnimalsElectrical signals through neuronsEndocrine System in AnimalsUses hormones to transmit messages over long distancesPlants also use hormonesSome transported through vascular systemOthers are released into the air
6Three Stages of Cell Signaling EXTRACELLULARFLUIDCYTOPLASMPlasma membrane11ReceptionThe receptor and signaling molecules fit together (lock and key model, induced fit model, just like enzymes!)ReceptorSignalingmoleculeSignaling molecule binds to the receptor protein
7Three Stages of Cell Signaling EXTRACELLULARFLUIDCYTOPLASMPlasma membrane11Reception2TransductionReceptor2nd Messenger!Relay molecules in a signal transduction pathwaySignalingmoleculeThe signal is converted into a form that can produce a cellular response
8Three Stages of Cell Signaling EXTRACELLULARFLUIDCYTOPLASMPlasma membrane1Reception2Transduction3ResponseReceptorActivationof cellularresponseRelay molecules in a signal transduction pathwayCan be catalysis, activation of a gene, triggering apoptosis, almost anything!SignalingmoleculeThe transduced signal triggers a cellular response
10Ion Channel Receptors Very important in the nervous system Gateclosed1IonsSignalingmolecule(ligand)Very important in the nervous systemSignal triggers the opening of an ion channeldepolarizationTriggered by neurotransmittersLigand-gatedion channel receptorPlasmamembrane2Gate openCellularresponse3Gate closed
12Transduction in a G-protein pathway FigFirst messengerAdenylylcyclaseG proteinG protein-coupledreceptorGTPATPSecondmessengercAMPTransduction in a G-protein pathwayProteinkinase ACellular responses
13Response Many possible outcomes Growth factorResponseReceptorReceptionMany possible outcomesThis example shows a transcription responsePhosphorylationcascadeTransductionCYTOPLASMInactivetranscriptionfactorActivetranscriptionfactorResponsePDNAGeneNUCLEUSmRNA
14Specificity of the signal SignalingmoleculeSpecificity of the signalThe same signal molecule can trigger different responsesMany responses can come from one signal!ReceptorRelaymoleculesResponse 1Response 2Response 3Cell A. Pathway leadsto a single response.Cell B. Pathway branches,leading to two responses.
15The signal can also trigger an activator or inhibitor The signal can also trigger multiple receptors and different responsesActivationor inhibitionResponse 4Response 5Cell C. Cross-talk occursbetween two pathways.Cell D. Different receptorleads to a different response.