Download - Warm-Up
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Warm-Up1. Why do you communicate?2. How do you communicate?3. How do you think cells
communicate?4. Do you think bacteria can
communicate? Explain.
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Cell CommunicationCHAPTER 11
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Do bacteria communicate?
Bonnie Bassler on How Bacteria “Talk”
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Cell SignalingAnimal cells communicate
by:Direct contact (gap junctions)Secreting local regulators
(growth factors, neurotransmitters)
Long distance (hormones)
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3 Stages of Cell Signaling:1.Reception: Detection of a signal
molecule (ligand) coming from outside the cell
2.Transduction: Convert signal to a form that can bring about a cellular response
3.Response: Cellular response to the signal molecule
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Reception
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Transduction
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Response
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1. ReceptionBinding between signal molecule (ligand) +
receptor is highly specific.Types of Receptors:
a) Plasma membrane receptor water-soluble ligands
b) Intracellular receptors (cytoplasm, nucleus)
hydrophobic or small ligands Eg. testosterone or nitric oxide (NO)
Ligand binds to receptor protein protein changes SHAPE initiates transduction signal
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Plasma Membrane Receptors
G-Protein Coupled Receptor (GPCR)
Tyrosine Kinase
Ligand-Gated Ion Channels
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G-Protein-Coupled Receptor
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G-Protein-Coupled Receptor
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Plasma Membrane Receptors
G-Protein Coupled Receptor (GPCR)
Tyrosine Kinase
Ligand-Gated Ion Channels
7 transmembrane
segments in membrane
G protein + GTP activates enzyme cell response
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Receptor Tyrosine Kinase
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Plasma Membrane Receptors
G-Protein Coupled Receptor (GPCR)
Tyrosine Kinase
Ligand-Gated Ion Channels
Attaches (P) to tyrosineActivate
multiple cellular responses at
once
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Ligand-Gated Ion Channel
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Plasma Membrane Receptors
G-Protein Coupled Receptor (GPCR)
Tyrosine Kinase
Ligand-Gated Ion Channels
Signal on receptor
changes shapeRegulate flow of
specific ions(Ca2+, Na+)
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2. TransductionCascades of molecular interactions relay
signals from receptors target moleculesProtein kinase: enzyme that
phosphorylates and activates proteins at next level
Phosphorylation cascade: enhance and amplify signal
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Second Messengerssmall, nonprotein molecules/ions that can
relay signal inside cellEg. cyclic AMP (cAMP), calcium ions
(Ca2+), inositol triphosphate (IP3)
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3. Response Regulate protein
synthesis by turning on/off genes in nucleus (gene expression)
Regulate activity of proteins in cytoplasm
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An Example of Cell Communication
http://learn.genetics.utah.edu/content/begin/cells/cellcom/
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Signal transduction pathways can be blocked or defective
Examples:DiabetesCholeraAutoimmune diseaseCancerNeurotoxins, poisons, pesticidesDrugs (anesthetics, antihistamines, blood
pressure meds)
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Cholera
Disease acquired by drinking contaminated water (w/human feces)
Bacteria (Vibrio cholerae) colonizes lining of small intestine and produces toxin
Toxin modifies G-protein involved in regulating salt & water secretion
G protein stuck in active form intestinal cells secrete salts, water
Infected person develops profuse diarrhea and could die from loss of water and salts
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ViagraUsed as treatment for erectile
dysfunctionInhibits hydrolysis of cGMP GMPProlongs signal to relax smooth muscle in
artery walls; increase blood flow to penis
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Apoptosis = cell suicideCell is dismantled and digestedTriggered by signals that activate cascade of
“suicide” proteins (caspase)Why?
Protect neighboring cells from damageAnimal development & maintenance
May be involved in some diseases (Parkinson’s, Alzheimer’s)
Interference may contribute to cancers
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Apoptosis of a human white blood cell
Left: Normal WBCRight: WBC undergoing apoptosis – shrinking and forming lobes (“blebs”)
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Effect of apoptosis during paw development in the mouse