Structure N Functions of CSM

8/13/2019 Structure N Functions of CSM

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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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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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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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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



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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)


Allow cells to sense changes in theexternal environment and respond to them



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FUNCTIONS OF THE CSM: RECEPTOR PROTEINS


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FUNCTIONS OF THE CSM: RECEPTOR PROTEINS


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An example of signal transduction


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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



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Attachment to cytoskeleton Membrane proteins may bebonded to components(microfilaments) of thecytoskeleton.

Some proteins may also adhereto the extracellular matrix .


Helps maintain cell shape

Pg 6 Fig. 6f

What is extracellular matrix?


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What is extracellular matrix? Pg 6 Fig. 6f



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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



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ECM

Pg 6 Fig. 6f



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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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Structure N Functions of CSM

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