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Cell Communication Reception, Transduction, Response.

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Presentation on theme: "Cell Communication Reception, Transduction, Response."— Presentation transcript:

1 Cell Communication Reception, Transduction, Response

2 Local signals Cells in a multicellular organism communicate by chemical messengers In local signaling, animal cells may communicate by direct contact, or cell-cell recognition Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3 local regulators - messenger molecules that travel short distances Paracrine signaling – local regulator released directly onto one cell by another Synaptic signaling – a nerve signal triggers the release of a local regulator onto a near by cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Local signals cont’d

4 Long Distance Signaling Hormones – chemical messengers that travel long distance. Ex. Through blood vessels

5 Signal Transduction Pathway After a signal is received a signal transduction pathway is a set of step that trigger a certain response from a cell. 1 Reception 2 transduction 3 response**** Ex. Yeast mating

6 Reception Reception – delivery of a signal to a cell Signal molecules are called ligands (ex.hormones) Water soluble ligands must bind to receptor proteins in the cell membrane Non-polar or small ligands can travel directly in the cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

7 G protein-coupled receptor – membrane receptor that activates a G protein when a ligand is present. (starts transduction) G protein – When activated, uses energy from GDP becoming GTP to turn on an enzyme. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings G protein-coupled receptor

8 Receptor tyrosine kinase - membrane receptors that attach phosphates to tyrosines. When the ligand is present the two kinases form a dimer and can trigger multiple transduction pathways. Receptor Tyrosine Kinase

9 ligand-gated ion channel – receptor opens like a gate when a ligand is present to allow ions in. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gated Ion Channels

10 Fig. 11-7d Signaling molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane Gate open Cellular response Gate closed 3 2 1

11 Intracellular (internal) Receptors Small or hydrophobic ligands travel directly through the cell membrane. They join to an internal receptor to form a hormone receptor complex (which begins transduction) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

12 Transduction Signal transduction usually involves multiple steps that includes turning a sequence of proteins on and off to get a response from the cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

13 Phosphorylation/Dephosphorylation Phosphorylation – add phosphates (turns protein on) Dedphosphorylation – removes phosphates (turns proteins off) Protein kinases – does phosphorylation Protein phosphatases- does dephosphorylation Phosphorylation Cascade

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15 Second Messengers Second messengers – small molecules that diffuse throughout the cell to carry the signal during transduction. Second messengers, cAMP (made from ATP), IP 3, Ca +, DAG**** Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

16 Fig G protein EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein-coupled receptor Phospholipase C PIP 2 DAG IP 3 (second messenger) IP 3 -gated calcium channel Endoplasmic reticulum (ER) Ca 2+ CYTOSOL Ca 2+ (second messenger ) GTP

17 Response Cell usually respond by synthesizing enzymes or proteins, or turning genes on or off. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

18 Fig Growth factor Receptor Phosphorylatio n cascade Reception Transduction Active transcription factor Response P Inactive transcription factor CYTOPLASM DNA NUCLEUS mRNA Gene

19 Fig Reception Transduction Response Binding of epinephrine to G protein-coupled receptor (1 molecule) Inactive G protein Active G protein (10 2 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (10 2 ) ATP Cyclic AMP (10 4 ) Inactive protein kinase A Active protein kinase A (10 4 ) Inactive phosphorylase kinase Active phosphorylase kinase (10 5 ) Inactive glycogen phosphorylase Active glycogen phosphorylase (10 6 ) Glycogen Glucose-1-phosphate (10 8 molecules)

20 Apoptosis Apoptosis – A response that is a programmed or controlled cell suicide A cell is chopped and packaged into vesicles that are digested to prevent enzymes from leaking out and damaging other cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

21 Triggering Apoptosis Apoptosis can be triggered by: –An extracellular death-signaling ligand –DNA damage in the nucleus –Protein misfolding in the endoplasmic reticulum Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

22 You should now be able to: 1.Describe the nature of a ligand-receptor interaction and state how such interactions initiate a signal-transduction system 2.Compare and contrast G protein-coupled receptors, tyrosine kinase receptors, and ligand-gated ion channels 3.List two advantages of a multistep pathway in the transduction stage of cell signaling 4.Explain how an original signal molecule can produce a cellular response when it may not even enter the target cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

23 5.Define the term second messenger; briefly describe the role of these molecules in signaling pathways 6.Explain why different types of cells may respond differently to the same signal molecule 7.Describe the role of apoptosis in normal development and degenerative disease in vertebrates Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings


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