Revision 2010 Unit 3 Cell Communication
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Transcript of Revision 2010 Unit 3 Cell Communication
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Cell Communication
Unit 3 AOS2 Review
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Types of SignalsPhysical stimuli• Light• Heat• Touch/mechanicalChemical stimuli – specific signalling
molecules• Nutrient molecules – glucose• Hormones: in animals and plants• Neurotransmitters• Pheromones• Electrical signals
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Communication Systems Involve Signal Transmission
• Signals are transmitted to targeted cells via:
• The Nervous System• A system of specialised cells providing rapid and precise signalling
between parts of the organism.
• Chemical signals (defined by the distance travelled) • Chemical messengers secreted by cells and carried via a transport
system to finally diffuse into the extra cellular fluid surrounding the target cell. (The Endocrine system is only one part)
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Long Distance Communication Can be Fast!
Signal initiated Signal transmitted Signal received
Nerve Cells (neurons) form nerve pathways. Information passes along a neuron as an electrical current. The impulse is unidirectional and fast!
Or slow… such as in the Endocrine System.
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Hydrophobic and Hydrophilic Signals
A return to the nature of molecules, importance of shape and binding specificity.
Membrane bound receptor
Intracellular receptor molecule
Hydrophilic signalling molecules
Neurotransmitters
Growth Factor HormonesInsulin
Hydrophobic Signalling MoleculesSteroid hormonesThyroid hormones
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Types of Plasma Membrane Receptors
Ion Channel Receptors (milliseconds)
Binding of ligand causes a shape change that opens the channel so ions enter or leave the cell. Eg: Acetycholine at nerve/muscle junctions
G protein-couple receptors (Seconds)
Binding of ligand activates a G protein which activates or inhibits an enzyme or modulates an ion channel that generates secondary messengers. Eg. Receptor for glucagon.
Tyrosine kinase-linked receptor (hours)
Binding of ligand to TK causes a shape change that activates enzymes within the cell. Eg: Human Growth Factor.
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Signal Transduction
• Applying the stimulus response model to the cell at a molecular level
• Is the signal hydrophobic or hydrophillic?• Does the cell have the correct receptor
molecules?• How is the signal transformed into a response
by a effector molecule?
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Intracellular receptors for hydrophobic signals
Steroid hormones activate receptors which regulate gene expression.
•Steroid hormones moves through the lipid bilayer
•Steroid binds with intracellular receptor
•The ligand-receptor complex moves into the nucleus to regulate gene expression
•Proteins are the products of gene expressions
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Hydrophilic signals
• The signal is received by a receptor on the cell membrane
• The signal passes along relay molecules – signal transduction.
• At the end of the relay effector molecules produce the cellular response
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The Cellular Response
• Effector molecules bring about a cellular response. These responses include:
• Activates or inhibits enzyme action.• Regulates protein production by switching
genes on or off.• Opens or closes protein channels.• Moves transport vesicles to the plasma
membrane to secrete cellular products.
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2006 Exam – Short Ans 2.
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2006 Exam – Short Ans 2.
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2006 Exam – Short 2
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2007 – MC Q 21