3Gap junctions between animal cells Plasmodesmata between plant cells Figure 11.4Plasma membranesGap junctions between animal cellsPlasmodesmata between plant cells(a) Cell junctionsFigure 11.4 Communication by direct contact between cells.(b) Cell-cell recognition
5Figure 11.5Local signalingLong-distance signalingTarget cellElectrical signal along nerve cell triggers release of neurotransmitter.Endocrine cellBlood vesselNeurotransmitter diffuses across synapse.Secreting cellSecretory vesicleHormone travels in bloodstream.Target cell specifically binds hormone.Local regulator diffuses through extracellular fluid.Target cell is stimulated.(a) Paracrine signaling(b) Synaptic signalingFigure 11.5 Local and long-distance cell signaling by secreted molecules in animals.(c) Endocrine (hormonal) signaling
8Relay molecules in a signal transduction pathway FigureEXTRACELLULAR FLUIDCYTOPLASMPlasma membrane1Reception2TransductionReceptorRelay molecules in a signal transduction pathwaySignaling moleculeFigure 11.6 Overview of cell signaling.
9Relay molecules in a signal transduction pathway FigureEXTRACELLULAR FLUIDCYTOPLASMPlasma membrane1Reception2Transduction3ResponseReceptorActivation of cellular responseRelay molecules in a signal transduction pathwaySignaling moleculeFigure 11.6 Overview of cell signaling.
26Activated relay molecule Figure 11.10Signaling moleculeReceptorActivated relay moleculeInactive protein kinase 1Active protein kinase 1Inactive protein kinase 2ATPPhosphorylation cascadeADPActive protein kinase 2PPPP iInactive protein kinase 3ATPFigure A phosphorylation cascade.ADPPActive protein kinase 3PPP iInactive proteinATPADPPActive proteinCellular responsePPP i
27Activated relay molecule Figure 11.10aActivated relay moleculeInactive protein kinase 1Active protein kinase 1Inactive protein kinase 2ATPPhosphorylation cascadeADPActive protein kinase 2PPPP iInactive protein kinase 3ATPADPActive protein kinase 3PFigure A phosphorylation cascade.PPP iInactive proteinATPADPPActive proteinPPP i
34First messenger (signaling molecule such as epinephrine) Figure 11.12First messenger (signaling molecule such as epinephrine)Adenylyl cyclaseG proteinG protein-coupled receptorGTPATPSecond messengercAMPFigure cAMP as a second messenger in a G protein signaling pathway.Protein kinase ACellular responses
38Inactive transcription factor Active transcription factor Figure 11.15Growth factorReceptionReceptorPhosphorylation cascadeTransductionCYTOPLASMInactive transcription factorActive transcription factorFigure Nuclear responses to a signal: the activation of a specific gene by a growth factor.ResponsePDNAGeneNUCLEUSmRNA
39Glucose 1-phosphate (108 molecules) Figure 11.16ReceptionBinding of epinephrine to G protein-coupled receptor (1 molecule)TransductionInactive G proteinActive G protein (102 molecules)Inactive adenylyl cyclaseActive adenylyl cyclase (102)ATPCyclic AMP (104)Inactive protein kinase AActive protein kinase A (104)Inactive phosphorylase kinaseFigure Cytoplasmic response to a signal: the stimulation of glycogen breakdown by epinephrine.Active phosphorylase kinase (105)Inactive glycogen phosphorylaseActive glycogen phosphorylase (106)ResponseGlycogenGlucose 1-phosphate (108 molecules)
41Ced-9 protein (active) inhibits Ced-4 activity Figure 11.21Ced-9 protein (active) inhibits Ced-4 activityCed-9 (inactive)Cell forms blebsDeath- signaling moleculeMitochondrionActive Ced-4Active Ced-3Other proteasesCed-4Ced-3NucleasesReceptor for death- signaling moleculeActivation cascadeInactive proteinsFigure Molecular basis of apoptosis in C. elegans.(a) No death signal(b) Death signal
42Ced-9 protein (active) inhibits Ced-4 activity Figure 11.21aCed-9 protein (active) inhibits Ced-4 activityMitochondrionFigure Molecular basis of apoptosis in C. elegans.Ced-4Ced-3Receptor for death- signaling moleculeInactive proteins(a) No death signal
43Death- signaling molecule Figure 11.21bCed-9 (inactive)Cell forms blebsDeath- signaling moleculeActive Ced-4Active Ced-3Other proteasesFigure Molecular basis of apoptosis in C. elegans.NucleasesActivation cascade(b) Death signal
44Cells undergoing apoptosis Figure 11.22Cells undergoing apoptosisSpace between digits1 mmInterdigital tissueFigure Effect of apoptosis during paw development in the mouse.