CH6 Cell Communication - CHAPTER 6: CELL COMMUNICA'ITON...

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Unformatted text preview: CHAPTER 6: CELL COMMUNICA'ITON Cell signaling in slime molds (kingdom Protista) - adverse conditions cause chWosTe/ium to secrete cyclic AMP (cAMP) Triggering the aggregation of to 100,000 amoebae to form a multicellular fruiting body Fruiting body with resistant spores at the end of a stalk Spore with thick coat Unicellular amoebae forage on Multicellular mound embedded in an ECM ivy Livmgston ® BIODIDAC 0 Cell sends d signal V ' l l v " V 9 Reception 9 Signal transduction Protein 1 Altered memb ra n e permea tulip}r o Respo n so forest floors Aggregation - amoeboe drawn together by cAMP (chemotaxis) Aggregating amoebae - Figure 6-1 p 135 Cell sends signal by synthesizing and releasing a signaling molecule (= ligand) OVERVIEW of CELL SIGNALING FIGURE 6-2 p 136 _ Reception: signaling molecule is “detected” by the target cell when it binds to a receptor protein in the plasma membrane, cytoplasm, or nucleus of target cellbactivating the receptor Signaling protein l Signal transduction: target cell converts extracellular signal into an intracellular signal; signal strength is increased (amplification) Protein that regulates a gene l l Altered Altered metabolism gene activity Enzyme Response — internal signal triggers a reaction by the target cell TYPES of CELL SIGNALING — FIGURE 6-3 p 137 1) Direct contact — recognition proteins in the membrane of one _ _ _ Recepior cell binds to a receptor protein In the membrane of another cell / N do UCIEUS——-____ _._ -. Signaling Target Cell Bignaling can molecules Receptor [local / 2) Paracrine signaling — secreting cell releases a J regu'am'l a V c J"- local regulator that diffuses to target cells nearby ‘ J J ” fl.“- ' ' ” '?_ Signaling Target can can a Receplor . ' Signaling . . . ' molcoules a ‘ 3) Synaptic signaling — neurons (nerve cells) release 1 : Km a neurotransmitter at a synapse with another cell .- ' "i, new” Signaling _ -- neuron _"' Signaling /Fieceifl€" molecules ' v ' {hormone} g _ 4) Hormonal signaling — long distance signaling v 3v j ~—-+ —-- ufi" between an endocrine cell that releases a hormone u ‘ 7 that is carried in the blood to target cells “ 5. . Hormone Endacnne Transpofled Tanget cell in blood 09 n _ _ _ _ mm” Cell-surface receptors are Hydrophilic Signaling a g _ _ I molecules in 1-he ECF ,3 "as: integral membrane proteins in the 5 __/' plasma membrane of target cells ‘ l i /' —‘\ ;\ F. if? Jl — r N ucieu s {3) Some Signaling molecules bind :0 receptors in the plasma membrane Hydrophobic signaling molecules cross me pic.st Intracellular receptors are membrane by simple diffusion “13 located in the cytosol or nucleus {bl Some signaling molecules bind to receptors inside the cell. TYPES of CELL SURFACE RECEPTORS I ' 0 Ian channel-linked receptors I . . _U . open or close when signaling :1 molecule binds to receptor 0 ion channel :5 closed. a When signaling molecule blnds to receptor. the channel opens. Sodium lat lon channel-linked receptor ions enter cell. Enzyme-linked receptors enzyme is activated or inactivated llllllllll ‘f l ill when signaling molecule binds o Receptors are In inactive state. 0 When $>9Mllflg molecule (ligand) binds to receptors, receptors are enzymatically phosphorylated. Phosphate comes horn ATP. (cl Emu-linked receptors CELL SURFACE RECEPTORS: 6 PROTEIN-LINKED RECEPTORS I G protein-linked receptors are integral proteins that activate G proteins — Figure 6-7 p 142 - Signaling Extracellular lluid melTule Me ’1 I 59mm” MSWM “we”? ' all”. Reclaim a e y We. _ ' rill-ill? lll'iltlllllll» inllllllll, ' an» Gyrosci o Signaling molecule binds with C1 protein-linked receptor 9 Signal molecule—receptor complex activates G proletn. in plasma membrane. GDP is replaced by GTF‘. Signaling MEHYM molecule kinase 1 kinase 2 kinase 3 04430 0%00 04—»00 Protein Phospho— Protein Phospho~ Protein Phospho— rylaiaa Matea rylarea a G protein activates adenylyl cyclese, which then cataiyzes WOT-Bl" Dwain Wain Synthesis of CAMP. l, l J, Alters metabolism Alters some cell activity Activates specific gene O cAMP activates protein kinase A. which then phosphorylates specific proteins, leading to some response in cell. Activated G protein stimulates or inhibits mother II membrane protein (enzyme or gated channel protein) CYCLIC AMP is a SECOND MESSENGER : Second messengers are ions and small molecules (non-profeins) produced in large quan'l'i'lies inside The cell when a first messenger (signaling molecule) binds 'l'o membrane bound receptors of i'l's surface Exiracellular fluid Signaling molecule (first messenger) Adenylyl 4 G protein cyclase o Signaling molecule combines with G protein—linked receptor. 6 protein activates adenylyl cyclase, which then catalyzes formation of CAMP from ATP. — Plasma membrane Second messenger 9 Signal is relayed by @ @ @ rapidly diffuses second messengers fhroughou‘l' cell a Response: Some Alters Aflecls Opens or closes activity is altered. metabolism gene activity ion channels TH’ CYCLIC AMP (CAMP) c second messenger C H made from ATP i i o no no Figure 6-2 p 136 | | ATP 0- o Adenylyl cyclase cafalyzes CAMP formal-ion O Phosphodiesferase HO C cafalyzes CAMP inac‘l'iva‘l'ion 9 H C 5’ AMP SIGN AL AMPLI FICA-EON Signaling 0 One signaling molecule Mum! s‘irengi'h of The signal mummanyfi. is magnified inside The cell mg- Figure 6-1 p 148 I a Each 6 protein activates an adenylylcyclase I I molecule. 9 Each adenylyl cyclase catalyzes production of many cAMP molecules. 9 Each DAMP molecule activates a protein kinase. Protein Protein Phoe‘ohorylatee proteins 0 9 Each protein kinese catalyzes phosphorylation of many Pmteins. o “9'5 90m 9 Final products affect “Hm many cell activities. INTRACELLULAR RECEPTORS most are Transcription factors Thai Signalling I'I'iOchLIlBS o Signaling molecules Y Target oeil pass through plasma membrane. ac‘iivaTe or repress specific genes Figure 6-10 p 145 r—— Signaling molecules That bind 'l'o intracellular receptors are small, hydrophobic ligands e9. steroid hormones e Signaling molecules move through cytosol. 9 Signaling molecules pass through nuclear envelope and combine with receptor in nucleus. o Activated receptor is a transcription factor that binds to and acu‘vanes (or re- presses] specific genes. Messenger 6 Proteins are synthesized. RNA / mm 0 Cell activity is altered. ...
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