4303 Cell Membrane

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CELL MEMBRANECELL MEMBRANE

MCB 4303MCB 4303MYCOLOGYMYCOLOGY


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INTRODUCTIONINTRODUCTION

Known as pKnown as plasma membranelasma membrane ororplasmalemmaplasmalemma

Resemble the “fluid mosaic” modals – theResemble the “fluid mosaic” modals – themolecules can constantly movesmolecules can constantly moves

Contains primarily lipids, protein and alsoContains primarily lipids, protein and alsosmall quantities of carbohydratessmall quantities of carbohydrates

Lipid bilayer - selectively semi-permeableLipid bilayer - selectively semi-permeable Can be disrupt by differentialCan be disrupt by differential

centrifuationcentrifuation


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FUNGAL PLASMALEMMAFUNGAL PLASMALEMMA

! thin ranular "cell coat#, ! thin ranular "cell coat#, semifluid, sheetli$esemifluid, sheetli$elayer of structurelayer of structure

%imilar to mammalian plasma membranes%imilar to mammalian plasma membranes &ormed the outermost boundary&ormed the outermost boundary

&unal cells - lac$ of cell wall - unit&unal cells - lac$ of cell wall - unitmembrane appear as three-layeredmembrane appear as three-layeredstructure under electron microscopestructure under electron microscope

'nner lihter line appro(imately )*'nner lihter line appro(imately )* !nstroms wide !nstroms wide


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COMPOSITIONCOMPOSITION

.rotein and sterols - form the lare part of.rotein and sterols - form the lare part ofthe cell membranethe cell membrane

/avin non-polar sterol erosterol, rather/avin non-polar sterol erosterol, ratherthan cholesterolthan cholesterol %terols-increase the stability of the plasma%terols-increase the stability of the plasma

membranemembrane

!mphipathic lipids - phospholipids and !mphipathic lipids - phospholipids andsphinolipidssphinolipids

composition depends upon the type ofcomposition depends upon the type ofspeciesspecies


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0olecule of phospholipid0olecule of phospholipid


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SphingolipidSphingolipid


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%pecific sterol "erosterol and 1yosterol#%pecific sterol "erosterol and 1yosterol#

with specific fatty acyl residues in thewith specific fatty acyl residues in the

phospholipid – responsible for the hihphospholipid – responsible for the hihtolerance of the cell membrane – to hihtolerance of the cell membrane – to hih

concentration of alcohol2 34 yeastconcentration of alcohol2 34 yeast

5he membrane component are tihtly5he membrane component are tihtlypac$ed with the sterols with unsaturatedpac$ed with the sterols with unsaturated

fatty acid side chainfatty acid side chain


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STRUCTURE OF MEMBRANESTRUCTURE OF MEMBRANE

.hospholipid - formed the lipid bilayer .hospholipid - formed the lipid bilayer

/ydrophilic heads - toward the surface/ydrophilic heads - toward the surface

/ydrophobic tails - buried in the interior/ydrophobic tails - buried in the interior

6ot a riid structure6ot a riid structure

Can assume a micellar confiuration -Can assume a micellar confiuration -arraned in spheres with their polararraned in spheres with their polar

roup outermostroup outermost


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.roteins are interspersed in the bilayer .roteins are interspersed in the bilayer

!mount - differs between species and !mount - differs between species and

accordin to functionaccordin to function 0ay coat on the surface, pro7ect into the0ay coat on the surface, pro7ect into the

phospholipid layer or span the entire width ofphospholipid layer or span the entire width ofthe membranethe membrane

%erve as molecular sinals which allow cells%erve as molecular sinals which allow cellsto communicate with each otherto communicate with each other

5here are several types of protein45here are several types of protein4


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"!# 'nteral protein"!# 'nteral protein 5ihtly bounded to the membrane5ihtly bounded to the membrane

Located spannin the membraneLocated spannin the membrane

have a hydrophilic cytosolic domainhave a hydrophilic cytosolic domainwhich interacts with internal moleculeswhich interacts with internal molecules

hydrophilic e(tra-cellular domain whichhydrophilic e(tra-cellular domain which

interacts with e(ternal molecules2interacts with e(ternal molecules2


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hydrophobic membrane-spanninhydrophobic membrane-spannin

domain which anchors it within the celldomain which anchors it within the cell

membranemembrane 5he hydrophobic domain consists of one,5he hydrophobic domain consists of one,

multiple, or a combination of 8-helicesmultiple, or a combination of 8-helices

and 9 sheet protein motifs2and 9 sheet protein motifs2 !lso $nown as !lso $nown as trans-membrane proteinstrans-membrane proteins22


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":# .eripheral protein":# .eripheral protein Located attached to interal proteins, orLocated attached to interal proteins, or

associated with the head roups ofassociated with the head roups of

membrane lipids2membrane lipids2 6ot in contact with the hydrophobic6ot in contact with the hydrophobic

membrane - associate only at themembrane - associate only at thecytosolic and e(tra-cellular faces2cytosolic and e(tra-cellular faces2

+nly temporary interactions with+nly temporary interactions withpermanent membrane proteinspermanent membrane proteins

!ble to dissociate to carry on its wor$ in !ble to dissociate to carry on its wor$ in

the cytoplasmthe cytoplasm


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"C# Lipid anchor protein"C# Lipid anchor protein Covalently bound to sinle or multipleCovalently bound to sinle or multiple

lipid moleculeslipid molecules

/ydrophobically insert into the cell/ydrophobically insert into the cellmembrane and anchor the proteinmembrane and anchor the protein

not in contact with the membranenot in contact with the membrane


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Structure cont!Structure cont!

&unus do not synthesis sterols&unus do not synthesis sterols

6ot necessary to the plasma membrane6ot necessary to the plasma membrane

structurestructure ;o not need them for normal veetative;o not need them for normal veetative

rowthrowth


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"ESICLES"ESICLES

Contain small membrane bounded vesiclesContain small membrane bounded vesicles

/as various function= implicated in apical/as various function= implicated in apical

rowth, upta$e of dyes and funicides "byrowth, upta$e of dyes and funicides "bypinocytosis#, the release of e(tracellularpinocytosis#, the release of e(tracellular

en1ymes and parasitism towards hiher planten1ymes and parasitism towards hiher plant

'ncluded lysosome, pero(isomes,'ncluded lysosome, pero(isomes,

lyo(ysomes, phaosomes, provacoules, olilyo(ysomes, phaosomes, provacoules, olivesicles and wall vesiclesvesicles and wall vesicles


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.art of the lysosomal comple( or endo-.art of the lysosomal comple( or endo-

membrane comple(membrane comple(

0ay fuse with one another or with larer0ay fuse with one another or with larermembrane-bounded oranelles or withmembrane-bounded oranelles or with

the plasmalemmathe plasmalemma

Chanes of the lipid bilayer to micellarChanes of the lipid bilayer to micellarconfiuration - facilitated the buddin andconfiuration - facilitated the buddin and

fusion of these vesiclesfusion of these vesicles


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&ormed by the separation and e(pansion&ormed by the separation and e(pansion

of the plasmalemma away from theof the plasmalemma away from the

underlyin structureunderlyin structure &usion of intracellular vesicles with the&usion of intracellular vesicles with the

membrane - e(cretes the contents of themembrane - e(cretes the contents of the

vesiclevesicle incorporates of the membrane to facilitateincorporates of the membrane to facilitate

the upta$e of nutrientsthe upta$e of nutrients


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FUNCTIONSFUNCTIONS

.rovides an effective barrier to many types of.rovides an effective barrier to many types ofmolecules - reulates the passae of materialsmolecules - reulates the passae of materialsinto and out of the cell - diffusion or activeinto and out of the cell - diffusion or active

transport "nutrients, ions, deto(ification#transport "nutrients, ions, deto(ification# .rotein function as transport protein and as.rotein function as transport protein and as

part of the membrane -part of the membrane - trans-membranetrans-membraneprotein comple(es, ion pumps, ion channels,protein comple(es, ion pumps, ion channels,and carrier proteinsand carrier proteins

%terols provide structure, modulation of%terols provide structure, modulation ofmembrane fluidity, and possibly control ofmembrane fluidity, and possibly control ofsome physioloic eventssome physioloic events


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%eparates the intracellular components from%eparates the intracellular components fromthe e(tra-cellular environmentthe e(tra-cellular environment

%erves as the attachment point for both the%erves as the attachment point for both the

intracellular cytos$eleton and cell wallintracellular cytos$eleton and cell wall Containin receptors –Containin receptors – 'dentification, cell'dentification, cell

interaction and reulation "hormones, antien#interaction and reulation "hormones, antien# 'nitial immunity'nitial immunity provide shape to the cellprovide shape to the cell Contain en1ymatic pumps that enerateContain en1ymatic pumps that enerate

enery - !5.enery - !5.


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S#nthe$i$ o% pl&$'& 'e'(r&neS#nthe$i$ o% pl&$'& 'e'(r&ne

.lasma membrane of funal consists of the.lasma membrane of funal consists of themain componentmain component erosterolerosterol

%ynthesis of both erosterol and cholesterol is%ynthesis of both erosterol and cholesterol isthrouh the demethylation of lanosterolthrouh the demethylation of lanosterol

Cytochrome .>* cataly1es the ? >-a-Cytochrome .>* cataly1es the ? >-a-demethylation of lanosteroldemethylation of lanosterol

5he imida1ole and tria1ole antifunal aents5he imida1ole and tria1ole antifunal aentsinterfere with cytochrome .>*-dependent ? >-interfere with cytochrome .>*-dependent ? >-a-demethylase - inhibits the formation ofa-demethylase - inhibits the formation oferosterolerosterol


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!ntifunal aents "amphotericin :# - interfere !ntifunal aents "amphotericin :# - interferewith the erosterol synthesiswith the erosterol synthesis

Results 4 plasma membrane permeabilityResults 4 plasma membrane permeabilitychanes and inhibition of rowthchanes and inhibition of rowth

3rosterol may be involved in reulatin chitin3rosterol may be involved in reulatin chitinsynthesis2synthesis2

'nhibition results a eneral activation of chitin'nhibition results a eneral activation of chitinsynthetase 1ymoen, leadin to e(cessivesynthetase 1ymoen, leadin to e(cessivechitin production and abnormal rowth2chitin production and abnormal rowth2


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Th&n)$ *ouTh&n)$ *ou

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4303 Cell Membrane