STRUCTURAL ORGANISATION OF CILIA AND FLAGELLA- IN PROKARYOTES AND EUKARYOTES TYPES OF FLAGELLA.pdf

STRUCTURAL ORGANISATION OF CILIA AND FLAGELLA-
IN PROKARYOTES AND EUKARYOTES
TYPES OF FLAGELLA

1. Dr. Manikandan Kathirvel M.Sc., Ph.D., (NET)
Assistant Professor,
Department of Life Sciences,
Kristu Jayanti College (Autonomous),
(Reaccredited with "A++" Grade by NAAC)
Affiliated to BengaluruNorthUniversity,
K. Narayanapura, Kothanur (PO)
Bengaluru 560077
Mobile: [phone]/
STRUCTURAL ORGANISATION OF CILIA AND FLAGELLA -
IN PROKARYOTES AND EUKARYOTES
TYPES OF FLAGELLA

2. Cilia

3. Cilia
•Ciliaaresmall,slender,hair-likestructurespresentonthesurfaceofallmammaliancells.
•Ciliaaremicroscopic,hair-likestructuresthatprojectfromthesurfaceofmanyeukaryoticcells.
•Theorganelleciliaarefoundineukaryoticcells.
•Ciliaaremembrane-boundstructureswiththeirmembranebeingcontinuouswiththeplasmamembrane.
•Unliketheplasmamembraneofcells,ciliarymembranehasbeenshowntocontaindistinctlipidsandproteins.
•Theyareprimitiveinnatureandcouldbesingleormany.
•Theycanbeoftwotypes–motileciliaandnon-motilecilia.
•Thenon-motileciliaareknownasprimaryciliaandactassensoryorganelles.
•Ciliaarestructurallyidenticaltoflagella.
•Prokaryotes(bacteria)donothavecilia
•Ciliaplayamajorroleinlocomotion.
•Theyarealsoinvolvedinmechanoreception.
•Theorganismsthatpossessciliaareknownasciliates.
•Theyusetheirciliaforfeedingandmovement.
Dependingonthetypeofcells,ciliaandflagellahavethefollowingfunctions:
•Propellingcells-Usingciliaorflagella,cellsareabletomovefreelyintheir
environment,especiallyinaquaticormoistenvironments.
•Sensoryfunctions-Someciliaandflagellaallowcellstosensechangesin
theirsurroundingswhichinturnallowsthecellstorespondappropriately.
•Transportingmaterial-Somecellsareabletonotonlytrap,butalsoguidethe
transportationofgivenmaterial.Thismayservetoengulfsuchmaterialintothe
cellorpreventunwantedmaterial/particles/microorganismsfrominvadingthe
cellortissue.
Cilia of respiratory tract

4. TypesofCilia
Followingarethetwodifferenttypesofcilia:
MotileCilia
Thesearefoundinlargenumbersonthesurfaceofthecell.Inhumans,thesearefoundintherespiratory
epitheliumoftherespiratorytract.Here,theyfunctionbyclearingthemucusanddustoutofthelungs.
•Motilecilia(9+2)canbefoundinbothhigheranimalsand
single-celledeukaryotes.Inmicroscopicorganisms(known
asciliates)motileciliaareusedforlocomotionorfor
movingfluidovertheirsurfacewhichcontributestothe
feedingprocess.
•Inhigheranimals,suchashumanbeings,motileciliacan
befoundinanumberoftissues(e.g.respiratoryepithelium
andfallopiantubes)wheretheyareeitherinvolvedinthe
clearanceoformovingofsubstances.
•Intherespiratorysystem,ciliatrapandremovedirt(as
wellasmucous)fromthelungsandotherpartsofthis
system.Inthefallopiantube,ontheotherhand,ciliaserve
tomovetheovumtotheuterus.

5. Non-motileCilia
PrimaryCiliaarenon-motileciliathatwerefirstdiscoveredin1898.Thesestructureswerelongbelievedtobevestigial
organelles.However,recentresearchespresentedthebiologicalrolesofprimaryciliathattheyfunctionasasensory
cellularantennathatcoordinatesalargenumberofcellularsignallingpathways.
Apartfromthese,theyalsohelpin:
•Properurineflowbysignallingthekidneycells.
•Theyactasmechanoreceptorsorsensoryreceptors.
•Theciliafunctionbypermittingthetransferofimportantparticlesfromonesideofthelight-sensitivecellstoanotherin
theretina.
•Ascomparedtomotilecilia,primarycilia(9+0)projectassingle
structuresfromcellbodies.Theyarefoundinvirtuallyallcellsin
allmammals.Theyareprimarilyinvolvedinsensoryfunctions
andthusallowgivenbodytissues/organstorespond
appropriately.
•Likemotilecilia,primaryciliaconsistofninedoublet
microtubulesthatmakeuptheaxoneme.Thesemicrotubules
originatefromthebasalbodythatalsoprovidesstability.
•Unlikemotilecilia,however,primaryciliadonotpossessdynein
armsandthecentralsingletmicrotubules(centralpair
microtubules).Thisisduetothefactthatprimaryciliaarenot
motileandthusdonotneedelementsnecessaryformotility.
Primaryciliaplayanimportantroleincell
signalingduringdevelopmentandhomeostasis.
Primarycilia(5-10uminlength)areexposedto
theextracellularenvironment,theyare
susceptibletovariousstimulithatcontributeto
theirroleinsignaling.
Inadditiontodetectingvariouschemicalfactors,
morphogensandgrowthfactorsinthe
extracellularmatrix,primaryciliaalsodetect
changesinpressureandfluidmovementacross
thecellsurface.
Structures that have no apparent function and appear to be residual parts from a past ancestor
are called vestigial structures. Examples of vestigial structures include thehuman appendix,
the pelvic bone of a snake

6. CiliaStructure
1.Ciliaaremadeupofmicrotubulescoatedbytheplasmamembrane.
2.Motileciliaarecharacterizedbyaradialpatternconsistingofnine(9)
outermicrotubuledoubletsthatsurroundtwosingletmicrotubules.
Eachciliumcomprisesninepairsofmicrotubulesthatformtheoutside
ringandtwocentralmicrotubules.
3.This9+2patternreferstotheninedoubletmicrotubulessurrounding
thetwomicrotubulesthatarecentrallylocated.Theringofmicrotubule
scaffolding,thisstructureiscalledanaxoneme.
4.Inadditiontothemicrotubules,whicharethemaincomponentsofthe
structure,motileciliaarealsocomposedofdyneinarmsandradial
spokesthatcontributetotheoverallmotilityofthestructure.
5.Theaxoneme(thebundleofmicrotubuleswhichmeasuresabout
0.25umindiameter)issurroundedbytheplasmamembraneandthe
wholestructure(cilia)canbeidentifiedunderthemicroscope.
6.Thenineouterpairsaremadeupofmotorproteinscalleddynein.
Thesearelargeandflexiblethatallowstheciliatomove.
7.Ciliaareattachedtothecellatthebasalbodythatismadeupof
microtubulesarrangedinninetriplets.
8.Atitsbase(whereitattachestothecell),theaxonemeisattachedto
cylindricalstructuresknownasbasalbodiesmeasureabout0.4umin
lengthand0.2uminwidthandaremadeupoftheAtubule(nine(9)
tripletmicrotubulesconsistingofprotofilamentmicrotubules),an
incompleteBtubuleaswellasanincompleteCtubule.
9.Apartfromanchoringciliainthecytoplasm,basalbodiesalsoplayan
importantroleintheassemblyofthesestructures.
DyneinisanATPasethatconvertstheenergy
releasedbyATPhydrolysisintothemechanical
workofciliaryandflagellarbeating

7. CiliaFunction
1.Theimportantfunctionsperformedbyciliainvolve
locomotionandsensoryfunctions.Theyplayamajor
roleincellcycleandreplicationandalsointhe
developmentofhumansandanimals.
2.Multipleciliamoveinarhythmicmotionthatkeepsthe
internalpassagewaysfreefrommucusoranyforeign
agent.Motileciliausetheirrhythmicundulationto
sweepawaysubstances,asinclearingdirt,dust,
micro-organismsandmucus,topreventdisease.
3.Afewnon-motileciliaactasanantennathatreceives
sensoryinformationforthecellsandprocessesthese
signalsfromthesurroundingfluids.E.g.thecilia
presentinthekidneybendforcefullyastheurine
passes.Thissendssignalstothecellsthattheurine
isflowing.
4.Thenon-motileciliafoundinthephotoreceptorsof
retinahelpinthetransportofmoleculesfromoneend
totheother.
5.Ciliaplayrolesinthecellcycleaswellasanimal
development,suchasintheheart.
6.Ciliaalsoplayaroleincellularcommunicationand
moleculartrafficking.

8. CiliaDisorders
Defectiveciliafunctionshavebeenassociatedwiththe
followingdiseaseanddiseasesyndromes:
•Ciliopathies:Itisageneticdisorderofthecilia
structures–thebasalbodiesorofciliafunction.
Dysfunctionordefectsinprimaryandmotileciliaare
knowntocausenumerousdistressinggeneticdisorders
knownasciliopathies.
•PrimaryCiliaryDyskinesia:Itisanautosomal
recessivedisorderinwhichtheciliadonotfunction
normally.Thisconditionpreventstheclearingofmucus
fromthelungs,earsandsinuses.
•Alstromsyndrome(progressivelossofvisionand
hearing,heartdiseasethatenlargesandweakensthe
heartmuscle,obesity,type2diabetes
•Meckel-Grubersyndrome(enlargedkidneys)
•Nephronophthisis(inflammationandscarring(fibrosis)
thatimpairskidneyfunction)
•Respiratoryinfections
•Anosmia(completelossofsmell)
•Maleinfertility

9. Amechanoreceptor,alsocalledmechanoceptor,isa
sensoryreceptorthatrespondstomechanicalpressureor
distortion.
Mechanoreceptorsdetectstimulisuchastouch,
pressure,vibration,andsoundfromtheexternaland
internalenvironments.

10. Flagella

11. Flagella
•Flagellaarethemicroscopichair-likestructuresthatareinvolved
inthelocomotionofthecells.Theword‘flagellum’itselfmeans
‘whip.’
•Aflagellum(plural:Flagella)maybedescribedasafilamentous
organelleusedforlocomotion.
•Likecilia(foundineukaryoticcells),flagellaalsoprotrudefrom
thebodyofthecellwhichallowsthemtoperformtheirfunctions
effectively.
•However,theyarelongerinlength,measuringbetween5and
20um.
•Thereareafeworganismsinwhichflagellaactassensory
organstoassistinthechangeofpHandtemperature.
•Theyareusuallyfoundinbacteria,archaea,andeukaryotes.
Cellsthatpossessthisstructurearereferredtoasflagellates
andpresentinbotheukaryoticandprokaryoticcells.
•Forinstance,apartfromamajorityofbacteriathatuseflagella
forlocomotion,thestructurecanalsobefoundonsuchsingle-
celledorganismsaseuglenaandprotozoaspecieslike
Trypanosomaevansi.
•Itcanbefoundongametesofvariousorganismsincluding
slimemolds,fungi,andanimals.

12. FlagellumStructure
Whileflagellacanbefoundinbotheukaryoticandprokaryoticcells(and
servethesamepurpose)therearevariousdifferenceswithregardsto
theirstructures/compositionaswellasthemechanismbywhichthey
functionbetweenthetwotypesofcells.
Theflagellafoundinprokaryoticcellsconsistofaglobularproteinknown
asflagellin.Here,theproteinwrapsaroundinahelicalmannerforminga
hollowcylinderalongthelengthofthestructure.Thisproteinisabsentin
eukaryoticflagellumwhereit'sreplacedbyproteinfilamentsknownas
microtubules.
Someofthedifferencesbetweenthetwoinclude:
•Prokaryoticflagellatendtobesmallerandlesscomplexcomparedto
eukaryoticflagella
•EukaryoticflagellaarepoweredbyATPwhilethoseofprokaryotesare
proton-driven
•Theprokaryoticflagellaarecharacterizedbyarotatormovementwhile
thoseofeukaryoticcellshavebendingfashion
•Prokaryoticflagellalackaplasmamembrane
Apartfromlength,thestructureandcompositionofeukaryoticflagella
aresimilartociliafoundinmanyeukaryotes

13. Bacterialflagellumiscomposedofthreemainpartsthatinclude:
1.Basalstructure(Rotarymotor)
2.Hook(actsastheuniversaljoint)
3.Filament(thehelicalpropeller)
1.Basalbody
•Inbacteria/prokaryotes,thebasalbodyisarodthatconsistsof
severalringsthatarelocatedwithinthecellmembrane.InGram-
negativebacteria,theringsincludetheL-ringthatispositionedin
theoutermembraneofthelipidbilayerandthePringwhichis
locatedinthepeptidoglycanlayer.
•Thebasalbodyisgenerallydividedintoseveralpartsthatinclude:
•Proteinrings(Cring,MSring,Pring,andLring)
•Rod
•Sleeve
Proteinringsserveastheprotonpumpsthatareinvolvedinthe
movementofhydrogenionsacrossthemembrane.It'sthis
movementofionsacrossthemembranethatultimatelyrotatesthe
ringsandthustheflagellum.
*Thebasalbody,aswellasthehook,alsoservestoanchorthe
filamentofthestructuretothesurfaceofthecell.
Theflagellaareahelical-likestructurethatis
composedofflagellinprotein.
Theflagellastructurecanbedividedintothreeparts,
namelyhook,basalbody,andthefilament.
•Thebasalbodyisattachedtothecellmembraneand
thecytoplasmicmembrane.
•Thehookisabroaderareathatispresentatthebase
ofthefilament.Itconnectsthefilamenttothemotor
proteininthebase,andthehooklengthisagram+ve
bacteria.
•Thefilamentisthehair-likestructurethatarisesfrom
thehook.

14. Genes encoding different proteins
L-ring-of thebacterialflagellumis the ring in the lipid outercell membrane
C ring –cytoplasmic ring
MS ring-isa transmembrane protein complex made of FliFand is the base for flagellarstructure, assembly and function (Inner membrane)
P ring-It is known to be embedded in the peptidoglycan cell wall.

15. 2.TheHook
•Consistingof120subunitsofasingleprotein,thehook
(whichisshortandcurved)actsastheuniversaljoint
thatconnectsthefilamenttothebasalbody.
•Unlikethebasalbody,thehookisnotembeddedinthe
plasmamembrane.However,itplaysacrucialrolein
themotilityandtaxisofbacteriathroughthe
transmissionofmotortorquetothefilament(propeller)
part of the structure.
•It'scomposedof4maindomainsthatarearrangedon
theinsideandoutsideofthestructurewhosenature
allowsforthedirectconnectionbetweenthehookand
therod.
•Thejunctionbetweenthehookandthefilament
consistsoftwoproteins(FlgKandFlgL)whichhave
beenshowntocontributetotheformationofthe
filamentpartofthestructure.

16. 3. The Filament
•Thefilamentistheelongatedpartoftheflagella.It'stubular
andconsistsof11protofilamentsthatresemblethosefoundin
therodandhookpartsofthestructure.
•Theflagellin,whichisthemaincomponentofthefilament,
alsoconsistsoffourdomainsthatformtheinnerandouter
partofthestructure.Thedirectiontowhichfilamentrotatesis
dependentonthemotorspinning(clockwiseor
counterclockwise).
Functions:
•Flagellafoundinorganismsasbacteria,archaea,andvarious
eukaryoticcellsareusedforswimmingthroughfluidaswellas
swarming
•Flagellahavebeenshowntohavesensoryfunctionsthat
allowcellstodetectchangesintheirenvironmentandrespond
effectively(todetectthepHandtemperaturechanges).
•Afeweukaryotesalsouseflagellumtoincreasereproduction
rates.
•Ingreenalgae,studieshavesuggestedthatflagellamayact
assecretoryorganelles.
Swarmingmotilityisarapidandcoordinatedtranslocationofabacterial
populationacrosssolidorsemi-solidsurfaces

17. Types of Flagella:
Organisms may be classified based on the number of
flagella on their surface.
These include:
•Atrichous-with no flagella
•Monotrichous-single flagellum originating from one
end
•Lophotrichous-several flagella at one pole
•Amphitrichous-single flagellum on both poles
•Peritrichous-multiple flagella across the surface of
their bodies
1.Monotrichousisasingleflagellumthatispresentat
oneendortheother.Thesehavetheabilitytorotate
clockwiseandanti-clockwise.
2.Thelophotrichousaretheseveralflagellumsthatare
attachedatoneendortheother.Theycanrotate
clockwiseandanti-clockwise.
3.Peritrichousaretheseveralflagellumsthatare
attachedallovertheorganism.Theyarenon-polar,
andtheycanrotateanti-clockwise.
4.Amphitrichousarethesingleflagellumthatisattached
toboththeendsoftheorganism.Theyarepolarand
canrotateclockwiseandanti-clockwise.

19. Difference Between Cilia and Flagella
Cilia
•Theyarepresentinlargenumbers.
•Theyaregroupedintothecategoryofprotozoans,classCiliata,intheCiliatedepitheliumoftheMetazoaand
otherclasses.
•TheyformCirribyfusingintosomeprotozoans.
•Ithassimilarstructuresandfunctionsasthatofflagella,butciliumisshorter,andmovementisquitedifferent.
•Itexhibitsradicalmotion.
•ItspresenceisfoundontheoutersurfaceofsomelarvaelikeMollusca,Annelida,andNemertines,which
thereforehelpitwiththelocomotion.
•Ciliaoftencovertheentirecell.
Flagella
•Theyarefewerinnumber.
•Flagellausuallydonotfuse.
•Theyarefairlylong.
•Thesearepresentinprotozoans,choanocytecellsofMetazoa,andinotherclasses-inplants,ingametecells,
andinalgae.
•Theyarefewerinnumber.
•Itexhibitsincoiledmotion.
•Theyareusuallyfoundatoneendofthecell.

20. Some examples of protozoa areAmoeba, Paramecium,
Euglena and Trypanosoma
Metazoans includeinsects, worms, jellyfish, octopus,
molluscs, birds, fish, amphibians, reptiles and
mammals, etc.