Structure N Functions of CSM
Transcript of Structure N Functions of CSM
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Announcements
Cellular Structure and Functions Self-directedLearning
E-learning lesson on LMS
Cellular structure online MCQ quiz on LMS Cells and Life Exhibition group assignment- Submit models to Bio Lab 1 ( 7:45-10:30 am
OR 2-4 pm ) and email Prezi link to respectivetutors by this Thursday 28 th MarchCell And Nuclear Division E-learning to be done
only on next Thursday ( AJ learning Day)
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Animal Cell Plant Cell
Cell surfacemembrane Cell surface
membrane
CELL MEMBRANE
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CELL MEMBRANE
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1. Basic Structure2. Functions3. Transport Across the Cell
surface membrane (CSM do
not use this short form in youranswers.)
CONTENTS
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Buzz with your neighbour Pg 1
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Link from cellular structures.
1. nuclear membrane
4. smooth ER
5. mitochondria
2. Golgi apparatus
3. rough ER
Pg 1
http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/eigeneEM/Colon/Col23Plz6.jpghttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/eigeneEM/Tph/Tph21c.jpghttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/eigeneEM/Colon/Col23Plz6.jpghttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/eigeneEM/Tph/Tph21c.jpg -
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Buzz with your neighbour Pg 1
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1. Basic Structurea) Phospholipids
b) Proteinsc) Cholesterold) Carbohydrates
2. Functions3. Transport Across the CSM
CONTENTS
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BASIC STRUCTURE OF CELL SURFACE MEMBRANE Pg 1
Dynamic, self-aggregating structure.
Held together by non-covalent interactions.
http://www.youtube.com/watch?v=Qqsf_UJcfBc
http://www.youtube.com/watch?v=Qqsf_UJcfBchttp://www.youtube.com/watch?v=Qqsf_UJcfBchttp://www.youtube.com/watch?v=Qqsf_UJcfBc -
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PHOSPHOLIPIDSPg 2
Cell membrane is a phospholipid bilayer
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PHOSPHOLIPIDSPg 2
How is the phospholipid bilayer formed?
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PHOSPHOLIPIDSPg 2
Cell membrane is a phospholipid bilayer
Phospholipid moleculesare amphipathic .
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Hydrophilic headcontaining polar phosphate group.
PHOSPHOLIPIDSPg 2
Hydrophobic tailcontaining non-polar
fatty acid chains.
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Hydrophilic phosphate head affinity for water
Hence face aqueous environment on either side of CSM Hydrophobic hydrocarbon/FA tails point away from
the aqueous environment, face inwards
BEHAVIOUR OF PHOSPHOLIPIDS IN WATERPg 2
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PHOSPHOLIPIDSPg 2
How is the phospholipid bilayer formed?
The phospholipids are assembled into abilayer with all the hydrophobic tailssandwiched between the two layers ofhydrophilic heads , forming ahydrophobic barrier .
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PHOSPHOLIPIDSPg 2
There can also be other arrangements when the
phospholipids gather together.
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PHOSPHOLIPIDSPg 2
Membranes are FLUID
Phospholipids are free to move
Phospholipids move laterally
Flip-flop (occasional)
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PHOSPHOLIPIDSPg 2
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PHOSPHOLIPIDSPg 2
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BASIC STRUCTURE OF CELL SURFACE MEMBRANE Pg 3
Proteins
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PROTEINSPg 3
Two populations of membrane proteins can be
found on the CSM. Integral/ intrinsic proteins Peripheral proteins
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PROTEINSPg 3
Two populations of membrane proteins can be
found on the CSM.
Membrane proteins
Integral/ intrinsicproteins
Transmembraneproteins
Other integralproteins
Peripheralproteins
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PROTEINSPg 3
INTEGRAL/ INTRINSIC PROTEINS Penetrate the hydrophobic core.
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PROTEINSPg 3
INTEGRAL/ INTRINSIC PROTEINS Penetrate the hydrophobic corea) Transmembrane protein : COMPLETELY span the entire
bilayer.b) Other integral proteins extend partway
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PROTEINSPg 3
INTEGRAL/ INTRINSIC PROTEINS Penetrate the hydrophobic corea) Transmembrane protein : COMPLETELY span the entire
bilayer.b) Other integral proteins extend partway
Why are proteins able to stay in the membrane?
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PROTEINSPg 4
INTEGRAL/ INTRINSIC PROTEINS Hydrophobic regions of proteins :
contains amino acids with hydrophobic R groups undergo hydrophobic interactions with the fatty acid tails
of the bilayer
Phenylalanine Tryptophan
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PROTEINSPg 3
INTEGRAL/ INTRINSIC PROTEINS Hydrophobic regions of proteins:
contains amino acids with hydrophobic R groups undergo hydrophobic interactions with the fatty acid tails
of the bilayer
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PROTEINSPg 3
INTEGRAL/ INTRINSIC PROTEINS Hydrophilic regions of protein :
Attach to microfilaments of cytoskeleton (inside the cell) Attach to fibres of extracellular matrix (outside the cell)
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PROTEINSPg 3
PERIPHERAL/ EXTRINSIC PROTEINS Not embedded in the bilayer at all Loosely bound/ float about
Peripheralprotein
Peripheralprotein
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BASIC STRUCTURE OF CELL SURFACE MEMBRANE Pg 4
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CHOLESTROLPg 4
Helps maintain membrane fluidity. HOW? Low temperature:
fluidity by disrupting the regular packing of phospholipids hinders solidification High/ moderate temperature:
cholesterol membrane fluidity by restraining phospholipidmovement.
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BASIC STRUCTURE OF CELL SURFACE MEMBRANE Pg 4
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CARBOHYDRATES Pg 4
short branching carbohydrate chainsSome proteins and lipids have
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CARBOHYDRATESPg 4
Protein+ Carbohydrate GLYCOPROTEIN
Lipid + Carbohydrate GLYCOLIPID
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CARBOHYDRATES Pg 4
Protein+ Carbohydrate GLYCOPROTEIN
Lipid + Carbohydrate GLYCOLIPID
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CARBOHYDRATES Pg 4This glycolipid is a sugar residue attached to aphospholipid. This glycolipid technically has glycerolcomponent which is part of the phospholipid.
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CARBOHYDRATES Pg 4Carbohydrates also form the glycocalyx coat, the layeroutside of the plasma membrane.
Functions of the glycocalyx:Protection : Cushions the plasma membrane and protects it
from chemical injury
Immunity to infection : Enables the immune system torecognise and selectively attack foreign organisms
Transplant compatibility : Forms the basis for compatibilityof blood transfusions, tissue grafts, and organ transplants
Cell adhesion : Binds cells together so that tissues do notfall apart
Fertilization : Enables sperm to recognize and bind to eggsEmbryonic development : Guides embryonic cells to their
destinations in the body
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FLUID MOSIAC MODEL Pg 4The cell surface membrane is described as aFLUID MOSAIC MODEL by Singer and Nicolsonin 1972.
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FLUID MOSIAC MODEL Pg 4The cell surface membrane is described as a
FLUID MOSAIC model
Phospholipids & proteins are
free to move laterally withinthe membrane &phospholipids are able to
move transversely within alayer.
Phospholipid bilayer is a dynamic structure where phospholipidsand proteins are in continuous motion .
Fluid:
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FLUID MOSIAC MODEL Pg 4The cell surface membrane is described as a
FLUID MOSAIC model
Phospholipids & proteins are
free to move laterally withinthe membrane &phospholipids are able to
move transversely within alayer.
Different proteins are
randomly embeddedand scattered in thephospholipid bilayer
Phospholipid bilayer is a dynamic structure where phospholipidsand proteins are in continuous motion .
Fluid:Mosaic:
CO S
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Basic Structure Functions Transport Across the CSM
CONTENTS
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FUNCTIONS OF THE CELL SURFACE MEMBRANE
PROTEINS
PHOSPHOLIPIDBILAYER (pg 1)
GLYCOLIPIDS/GLYCOPROTEINS
(bottom of pg 6)
TransportEnzymaticSignal transduction (as cell surface receptors)Cell-to-cell recognitionIntracellular joining
Attachment to cytoskeleton Forms a hydrophobic barrier
Compartmentalise the cell .separate the contents of the cell from theexternal environment.maintenance of a constant internal
environment within the cell.
Signal transduction (as cell surfacereceptors)
Cell-to-cell recognition
Pg 5
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Channel proteins are transmembrane proteinsthat provide hydrophilicchannels for selectivepassage of small ions &polar molecules(hydrophilic).
FUNCTIONS OF THE CSM: TRANSPORT PROTEINSPg 5
Carrier proteinsShuttle substances bychanging shape- May be passive
- May be active(requires energy, ATP)
Enable regulation of passage of substances in / out of cell
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Enzymatic proteins
Embedded in membrane Active site exposed to adjacent solution
to bind substrate Can be organised together to carry out
sequential steps of a metabolicpathway.
FUNCTIONS OF THE CSM: ENZYMATIC PROTEINSPg 5
Involvement in a certain metabolic pathway
FUNCTIONS OF THE CSM RECEPTOR PROTEINS
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Signal transduction
Receptor protein embedded in membranehas a:
Binding siteo exposed to outside of cello has a specific complementary
shape that fits the shape of a ligand(chemical messenger e.g. hormone,growth factor, neurotransmitter)
FUNCTIONS OF THE CSM: RECEPTOR PROTEINSPg 5
FUNCTIONS OF THE CSM RECEPTOR PROTEINS
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Signal transduction
Binding of the ligand:o causes conformational change in
receptor proteino relays the signal to the inside of the
cell (by binding to cytoplasmic proteins)
FUNCTIONS OF THE CSM: RECEPTOR PROTEINSPg 5
Allow cells to sense changes in theexternal environment and respond to them
FUNCTIONS OF THE CSM RECEPTOR PROTEINS
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FUNCTIONS OF THE CSM: RECEPTOR PROTEINSPg 5
FUNCTIONS OF THE CSM RECEPTOR PROTEINS
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FUNCTIONS OF THE CSM: RECEPTOR PROTEINSPg 5
FUNCTIONS OF THE CSM RECEPTOR PROTEINS
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FUNCTIONS OF THE CSM: RECEPTOR PROTEINSPg 5
FUNCTIONS OF THE CSM RECEPTOR PROTEINS
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FUNCTIONS OF THE CSM: RECEPTOR PROTEINSPg 5
FUNCTIONS OF THE CSM: RECEPTOR PROTEINS
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FUNCTIONS OF THE CSM: RECEPTOR PROTEINSPg 5
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FUNCTIONS OF THE CSM: RECEPTOR PROTEINS
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FUNCTIONS OF THE CSM: RECEPTOR PROTEINSPg 5
An example of signal transduction
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An example of signal transduction
An example of signal transduction
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An example of signal transduction
http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-
bound_receptors_that_activate_g_proteins.html
FUNCTIONS OF THE CSM: CELL TO CELL RECOGNITION
http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.htmlhttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.html -
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Cell-to-cell recognitionGlycoproteins: Serve as cell identity markers . Each cell has its own unique
specific markers that can berecognised by membraneproteins of other cells.
This type of cell-cell binding isusually short-lived as comparedto that for intercellular joining.
FUNCTIONS OF THE CSM: CELL-TO-CELL RECOGNITIONPg 6
Enables cell-to-cell recognition(cells to recognize other cells)
FUNCTIONS OF THE CSM: CELL TO CELL ADHESION
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Cell-to-cell adhesion
Membrane proteins ofadjacent cells attached
together formingintercellular junctions . This type of cell-cell binding is
usually more long-lasting than that for cell-to-cell
recognition.
FUNCTIONS OF THE CSM: CELL-TO-CELL ADHESIONPg 6
Enables cell-to-cell adhesion
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FUNCTIONS OF THE CSM: ATTACHMENT TO CYTOSKELETON
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FUNCTIONS OF THE CSM: ATTACHMENT TO CYTOSKELETONPg 6 Fig. 6f
What is cytoskeleton? Pg 6 Fig 6f
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A network of fibres extending throughout the cytoplasm
Composed of microtubules, microfilaments andintermediate filaments (made up of protein subunits)
Functions: Give mechanical support to cell, maintain shape of
cell, motility (e.g. microtubules helps direct themovement of chromosomes during cell division,movement of vesicles)
What is cytoskeleton? Pg 6 Fig. 6f
What is the cytoskeleton? Pg 6 Fig 6f
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What is the cytoskeleton? Pg 6 Fig. 6f
FUNCTIONS OF THE CSM: ATTACHMENT TO CYTOSKELETON
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Attachment to cytoskeleton Membrane proteins may bebonded to components(microfilaments) of thecytoskeleton.
Some proteins may also adhereto the extracellular matrix .
FUNCTIONS OF THE CSM: ATTACHMENT TO CYTOSKELETON
Helps maintain cell shape
Pg 6 Fig. 6f
What is extracellular matrix?
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What is extracellular matrix? Pg 6 Fig. 6f
What is extracellular matrix?
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Substance produced by cells and excreted to theextracellular space within the tissues, serving as ascaffolding to hold tissues together.
Composed of proteins and polysaccharides.
What is extracellular matrix? Pg 6 Fig. 6f
What is extracellular matrix?
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What is extracellular matrix?
ECM
Pg 6 Fig. 6f
FUNCTIONS OF THE CELL SURFACE MEMBRANE
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FUNCTIONS OF THE CELL SURFACE MEMBRANE
PROTEINS
PHOSPHOLIPIDBILAYER (pg 1)
GLYCOLIPIDS/GLYCOPROTEINS
(bottom of pg 6)
TransportEnzymatic
Signal transduction (as cell surface receptors)Cell-to-cell recognitionIntracellular joining
Attachment to cytoskeleton Forms a hydrophobic barrier
Compartmentalise the cell .separate the contents of the cell from theexternal environment.maintenance of a constant internal
environment within the cell.
Signal transduction (as cell surfacereceptors)
Cell-to-cell recognition
Pg 5
CONTENTS
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Basic Structure Functions Transport Across the CSM
CONTENTS
Transport Across the CSM
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