cell communication chapter 11 - abridged. slide 2 of 23 cell-to-cell communication critical for...
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Cell Communication
Chapter 11 - Abridged
Slide 2 of 23
Cell-to-Cell Communication
Critical for multicellular organisms Trillions of cells must communicate in order to
coordinate their activities
Recent research indicates: cancer results from corrupted communication
Unimportant for the AP Exam Crucial for understanding the breakthroughs in cancer
and genetics that are occurring almost monthly now
Slide 3 of 23
Recent Nobel Prizes in Medicine
2001 – Hartwell, Hunt, & Nurse – cyclin pathways and cell cycle regulation (yeast)
2002 – Brenner, Sulston, Horvitz – used C. elegans to elucidate the mechanism of apoptosis
2006 – Fire & Mello - used C.elegans to discover the pathway of RNA interference
Slide 4 of 23
Simon Sez…
Signaling is a lot like the game “Simon Says…”
The signal is received: the game players hear: “Simon says take a step forward”
The signal is transduced: players must decide whether to step forward or not
The signal elicits a response: players step forward if the command was preceded by “Simon says”
Slide 5 of 23
3 Stages of Signaling
Thesis: external signals are received & converted to responses within the cell
1. Reception Signaling molecule binds to receptor protein = Shape Change
2. Transduction Cascades of molecular interactions relay signals from
receptor proteins to target molecules in the cell
3. Response Regulation of transcription or cytoplasmic activities
Slide 6 of 23
1st form of signaling
Yeast (fungi) mating
Process:1.Release mating factor2.Receive complementary factor3.????4.Response: grow toward opp. Type5.Nuclei fuse = genetic recombination
Slide 7 of 23
Overview of Cell Signaling
Slide 8 of 23
View Animation
11_06 SignalingOverview_A.swf
Slide 9 of 23
Reception
Reception involves getting the signal to the correct receiver
Only certain cells have the correct receptor = only certain cells can receive the signal
Signaling molecule usually called ligand receptor-ligand binding causes a conformational change
in the receptor molecule (remember induced fit?) Conformational change = Activation of the receptor
molecule
Slide 10 of 23
2 Types of Signal Receptors
1. Plasma Membrane Receptors Hydrophilic or water-soluble ligands or signal molecules G Protein-Coupled Receptors (GPCR) Receptor Tyrosine Kinase (RTK) Ion Channel Receptors
2. Intracellular Receptors
Hydrophobic or Nonpolar ligands
Carry out transduction by themselves
Slide 11 of 23
View Animation
11_13SignalTransduction_A.swf
Slide 12 of 23
G Protein-Coupled Receptor
Slide 13 of 23
Receptor Tyrosine Kinase (RTK)
Amplification
Kinase = enzyme for transfer of phosphate group
Slide 14 of 23
Ligand-Gated Ion Channel
Membrane receptor with a region that acts as a “gate” when the receptor changes shape.
When the signal molecule binds, gate opens or closes
Important in the nervous system
Slide 15 of 23
Intracellular Receptor
Hydrophobic signal molecules
Testosterone
Most intracellular receptor signals do the entire transduction on their own
Testosterone behaving as a transcription factor
-- controls which genes (DNA) are transcribed into mRNA
Slide 16 of 23
Transduction
Multistep Pathway
Transduction = shape change
Signal amplification
Signal Transduction Pathways often involve a phosphorylation cascade
Molecule is phosphorylated = activated Phosphate removed = deactivation
Slide 17 of 23
Protein Kinases (PK) -- enzymes that transfer phosphate groups
Protein Phosphatases (PP) -- enzymes that remove phosphate groups
Slide 18 of 23
Second Messengers
1st messenger = receptor Only GPCR & RTK have 2nd messengers
Other important component of transduction pathways Most components are enzymes or proteins
Small & polar
Calcium Ions & Cyclic AMP
Initiate a phosphorylation cascade
Slide 19 of 23
Response
Response may occur in the cytoplasm or nucleus
2 Types of typical response:1. Enzyme activity is regulated (turned on or off)2. Synthesis of enzymes is regulated (promoted or inhibited)
Transcription Factors – control which genes are transcribed (DNA RNA)
Slide 20 of 23
Transcription Factors
Slide 21 of 23
GF = Growth factor
RTK = Receptor Tyrosine Kinase
Ras = G Protein Associated with tumor growth
Rho = G protein
Slide 22 of 23
RTK = Receptor Tyrosine Kinase
GPCR – G-protein coupled receptor
Apoptosis = Programmed cell death
PDK1 = Protein dehydrogenase kinase
Akt = Protein kinase -- Involved in apoptosis
Slide 23 of 23
Day 1 Complete
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