CELL -Structural and Functional unit of life.pdf

This presentation offers the bird's eye view of the cell as the basic structural and functional unit of life. It also addresses the origin of eukaryotic cells from the prokaryotic cell by the endosymbiotic theory.

1. CELL BIOLOGY
Welcome to the topic:
Cell as unit of Structure & Function
by
Dr. N.Sannigrahi, Associate Professor of Botany,
Nistarini College, Purulia(W.B) India

2. EUKARIOTES AND ENDOSYMBIOTIC THEORY
•COURSE CONTENTS
•The Cell: Cell as a unit of structure and function;
•Characteristics of prokaryotic and eukaryotic cells;
•Different Cell organelles,
•Comparative account between prokaryotic and eukaryotic cell
•Origin of eukaryotic cell (Endosymbiotic theory).
•Significance of this theory.

3. CELL-THE BASIC UNIT OF LIFE
•Cell is a unit of biological activity delimited by a semi permeable membrane and capable of self
reproduction in a medium free from other living system’-A.G. Loewy and P. Siekevitz(1963).
ThecellwasfirstdiscoveredbyRobertHookein1665.
TheModerncelltheoryorcelldoctrineadvocates-
Alllivingorganismsarecomposedofcell,
Cellisthestructuralandfunctionalunitoflivingorganisms,
Allcellsarisefromthepre-existingcellsofsimilarkind,
Thechemicalcompositionandmetabolismofallcellsarebasicallysimilar,
Thefunctionofanorganismasawholeistheoutcomeoftheactivitiesandinteractionsofthe
constituentcells,
Eachcellcontainsgenerallyacentrallyplacednucleusandmanyotherorganelles,
Cellisthestorehouseofgeneticinformationandvehicleofexpression,
Energyflowoccursincell.

4. PROKARIOTIC & EUKARIOTIC CELL

5. Cell-Structural & Functional unit of Life
•Acellisthesmallestlivingthinginthehumanorganism,andalllivingstructuresinthehuman
bodyaremadeofcells.Therearehundredsofdifferenttypesofcellsinthehumanbody,which
varyinshape(e.g.round,flat,longandthin,shortandthick)andsize(e.g.smallgranulecellsof
thecerebelluminthebrain(4micrometers),uptothehugeoocytes(eggs)producedinthefemale
reproductiveorgans(100micrometers)andfunction.However,allcellshavethreemainparts,the
plasmamembrane,thecytoplasmandthenucleus.Theplasmamembrane(oftencalledthecell
membrane)isathinflexiblebarrierthatseparatestheinsideofthecellfromtheenvironment
outsidethecellandregulateswhatcanpassinandoutofthecell.Internally,thecellisdivided
intothecytoplasmandthenucleus.Thecytoplasm(cyto-=cell;-plasm=“somethingmolded”)is
wheremostfunctionsofthecellarecarriedout.Itlooksabit-likemixedfruitjelly,wherethe
wateryjellyiscalledthecytosol;andthedifferentfruitsinitarecalledorganelles.Thecytosol
alsocontainsmanymoleculesandionsinvolvedincellfunctions.Differentorganellesalso
performdifferentcellfunctionsandmanyarealsoseparatedfromthecytosolbymembranes.

6. CONTINUATION------------
•Thelargestorganelle,thenucleusisseparatedfromthecytoplasmbyanuclearenvelope
(membrane).ItcontainstheDNA(genes)thatcodeforproteinsnecessaryforthecelltofunction.
•Generallyspeaking,theinsideenvironmentofacelliscalledtheintracellularfluid(ICF),(intra-=
within;referredtoallfluidcontainedincytosol,organellesandnucleus)whiletheenvironment
outsideacelliscalledtheextracellularfluid(ECF)(extra-=outsideof;referredtoallfluid
outsidecells).Plasma,thefluidpartofblood,istheonlyECFcompartmentthatlinksallcellsin
thebody.
•Theintegrationofthecellismaintainedbythecytoskeletonandthecellwallcoifersprotection
andcellmembranemaintainaselectivepermeabilitytodesignthecellasanosmoticsystem.In
additiontothese,differentmembraneandnon-membraneboundorganellesalongwithother
substancesmakethecellasthestructural&functionalunitoflife.

7. ULTRASTRUCTURE OF PROKARIOTIC CELL

8. ULTRASTRUCTURE OF EUKARIOTIC CELL

9. DIFFERENCE BETWEEN PROKARIOTES AND EUKARIOTES
FEATURES PROKARIOTIC CELL EUKARIOTIC CELL
Cellular organizationMostly unicellular with 1-10 nm. Mostly multicellular with 10-100nm
Cell wall Present with mucopeptideor peptidoglycan Cell wall in plant without mucopepetide
Nucleus True nucleusabsent, only nucleoid, All features of true nucleus present
Chromosome True chromosomes absent, DNA without histoneChromosome with DNA & histone
Organelles Membrane bound organelles absent Membrane bound organelles present
Ribosome Smaller of 70S with 50S & 30S Larger of 80S type-60S & 40S
MitoticapparatusAbsent Present
Cell Cycle Shorter; 20-30minutes duration Longer with 12-24 hrs
Centioles Absent Present
MicrotubulesAbsent Present
Plasmids Present of diverse types like Rec. PlasmidsAbsent
Sexual ProcessParasexuality Typical sexuality
Endocytosis &
exocytosis
Absent Present

10. CELL MEMBRANE -PROTEIN ICEBERGS IN THE SEA OF
LIPID
•Theplasma(cell)membraneseparatestheinnerenvironmentofacellfromtheextracellularfluid.
Itiscomposedofafluidphospho-lipidbi-layer(twolayersofphospholipids)asshownandother
molecules.Notmanysubstancescancrossthephospholipidsbi-layer,soitservestoseparatethe
insideofthecellfromtheextracellularfluid.Othermoleculesfoundinthemembraneinclude
cholesterol,proteins,glycolipidsandglyco-proteinsbelow.Cholesterol,atypeoflipid,makesthe
membranealittlestronger.Differentproteinsfoundeithercrossingthebilayer(integralproteins)
oronitssurface(peripheralproteins)havemanyimportantfunctions.Channelandtransporter
(carrier)proteinsregulatethemovementofspecificmoleculesandionsinandoutofcells.
Receptorproteinsinthemembraneinitiatechangesincellactivitybybindingandrespondingto
chemicalsignals,suchashormones(likealockandkey).Otherproteinsincludethosethatactas
structuralanchorstobindneighboringcellsandenzymes.Glycoproteinandglycolipidsinthe
membraneactasidentificationmarkersorlabelsontheextracellularsurfaceofthemembrane.
Thus,theplasmamembranehasmanyfunctionsandworksasbothagatewayandaselective
barrier.

11. CELL MEMBRANE

12. CELL ORGANELLES
Anorganelleisanystructureinsideacellthatcarriesoutametabolicfunction.Thecytoplasm
containsmanydifferentorganelles,eachwithaspecializedfunction.(Thenucleusdiscussed
aboveisthelargestcellularorganellebutisnotconsideredpartofthecytoplasm).Many
organellesarecellularcompartmentsseparatedfromthecytosolbyoneormoremembranesvery
similarinstructuretothecellmembrane,whileotherssuchascentriolesandfreeribosomedonot
haveamembrane.
Letuslearnthestructureandfunctionsofdifferentorganellessuchasmitochondria(whichare
specializedtoproducecellularenergyintheformofATP)andribosome(whichsynthesizethe
proteinsnecessaryforthecelltofunction).Membranesoftheroughandsmoothendoplasmic
reticulumformanetworkofinterconnectedtubesinsideofcellsthatarecontinuouswiththe
nuclearenvelope.TheseorganellesarealsoconnectedtotheGolgiapparatusandtheplasma
membranebymeansofvesicles.Differentcellscontaindifferentamountsofdifferentorganelles
dependingontheirfunction.Forexample,musclecellscontainmanymitochondriawhilecellsin
thepancreasthatmakedigestiveenzymescontainmanyribosomeandsecretaryvesicles.

13. CELL ORGANELLES IMAGES

14. CELL ORGANELLES -FUNCTION

15. PLANT CELL STRUCTURE

16. MITOCHONDRIA
Mitoochondria’derivedfromMitos:thread.Chondrion:grain,popularlycalledpowerhouseofcell
andthestorehouseofenergy,
FirstdiscoveredbyKollikerin1850butBendacoinedtheterm,
Variableinshapebutcylindricalortubular(yeast)tospherical,filamentous,club-shaped,
Width0.05µm-1.0µminwidthand1.5-10µminlength,,with5-10dayslifespan,animalcellscontain
highermitochondriathanplantcells;kidneycellwith300-400,hepaticcells2with1000,musclecells
5,00,000,
Chemicallycontainsproteins60-70%,lipids25-35%,RNA5-10%,DNAinsmallamountwithlittle
mineraltracesandmorethan60diverseenzymes,
Outermembranewithmitochondrialenvelope,integralproteins,porinsthatformchannelsfor
permeabilityofsoluteandmetabolites,outerandinnermembrane,
Innersemi-permeablemembraneswithdifferentcarrierproteins,electroncarrier,couplingfactorsand
enzymeswithtwosurfaces-C-face&M-face,
Fingerlikefoldingtowardsinnersideknownascristaeormitochondrialcrests,numerousstalked
tennislikeparticlesknownasoxysomesasF0-F1particleswith10000-100000permitochondria.
Threeparts-abase,astalkandaheadfunctioningasATPaseforphosphorylation.

17. MITOCHODRIA -STRUCTURE & FUNCTION

18. MITOCHONDRIA
Inter-membranespace-normalspacebetweentheouterandinnermembraneofmitochondrionknown
asperichondrialspacewhosewidthis60-100Ȧ,extendedintointracristalspace,thischamberisfilled
withafluidcontainingenzymesandstoreATPmoleculesaftersynthesis,
Matrix-Centralspaceenclosedbytheinnermembraneknownasmitochondrialmatrix,densesemi
fluidcontainingproteins,lipids,enzymesofKrebsCycle,aminoacidsynthesis,fattyacidsynthesis;
doublestrandedDNAmolecules,RNAmolecules,70Sribosome,granulesofinorganicsalt,mtDNA
codesfor2rRNAs,19tRNAsandmRNAscodeforproteinsynthesis.
FUNCTION
SiteforcellularrespirationingeneralandTCAcycleinparticular,
ActsasATPmillofthecelltoproduceATPcurrency,
Differenttypesofsubstrateslikecarbohydrates,proteinsadfatsaremainlyoxidizedanddegraded
throughmitochondriaitactsasthecentreofmetabolicpool,
SiteofthesynthesisofBiomoleculeslikeChlorophyll,cytochrome,steroids,alkaloids,aminoacids
etc,
Itisthemitochondrialinheritancethatpassfrommothertooffspringviacytoplasmofeggresponsible
fordifferentgenetictraits-eithergoodorbad.

19. CHLOROPLASTS
Chloroplastsderivedfromchloros:green,plastos:moulded,greenplastidscontainingchlorophyll
pigmentsthatperformphotosynthesisbytheanabolicprocesses,
A.Schimper(1883)dividedplastidsintothreecategories-Leucoplastsi.e.colorlessplastids,
Chromoplastsi.e.coloredandChloroplastsi.e.greenplastids,
Derivedfromcommonprecursorcalledproplasts;ChloroplastsfirstobservedbyN.Grew(1862),
Numberofchloroplastsvariespercell,1inChlorella,UlothrixandChlamydomonas,16inSpirogyra,
20-40inmesophyllcellsofleafandseveralhundredinCharaand40000in1mmofRicinusleaf.
Variableinshape;cup-shapedinChlamaydomonas,ribbonshapedinSpirogyra,collarlikeinUlothrix
,discoidinVoucheriaetc.
Biochemicallyincontains50-60%proteins,20-30%lipid,5-10%chlorophyll,1-2%Carotenoids,1-
2%RNA,0.5%DNAandothermineralelements,Quinone,Vitamin-E&Ketc.
4-10µmindiameterand2-4µminthickness,
Boundedbytwolipoproteinsmembranes–outerandinnermembranewithperi-plastidialspace;inner
membraneencloseswithamatrixcalledstromahavingsmallcylindricalstructuresknownasgranum;
innermembranedevelopinfoldingslamellarstructurescalledthylakoids,

20. PLASTIDS-STRUCTURE & FUNCTION

21. CHLOROPLASTS
Thylakoidmembranepossesschlorophyllmolecules,Carotenoids,cytochrome,quinones,ATP
synthetase,etc
PhotosystemI(PSI)andPhotosystemII(PSII)andtheirphotochemicalreactioncenters(PRC)are
presentinthethylakoid,
PSIismoreabundantinstromalamellaeandPSIImoreingranumlamellae;PRCisaspecial
chlorophyllmoleculepresentbothinPSI&PSII,
Thestromacontainsosmophilicdroplets,proteins,lipids,starchgrains,DNA,RNA,70Sribosome,
enzymes,metalionsetc.,
Itissemiautonomousasitsynthesizesitsownproteinsandenzymesbyfollowingcentraldogma,
Stigmaoreyespotpresentinchloroplastinsomemotilealgae,containsphotoreceptorbeing
photosensitive;photosyntheticbacteriacontainsbacterio-chlorophyllandbacterioviridin.
FUNCTION:Photosynthesisasthekitchenhouseofcell,Carbonassimilation,storageofstarch,
evolutionofoxygen,FormationofATPbyphotosyntheticphosphorylationbynon-cyclicmethod
mostly,formationofreducingpowersintheformofreducedNADP,photosensitivitybythe
possessionofstigmaoreyespotalongwithfattyacidsandaminoacidsynthesisaresomeofthe
functionextendedbythechloroplasts.

22. RIBOSOMES-SUB UNITS & FUNCTION

23. RIBOSOMES-SUB UNITS & FUNCTION
A complex amembranous organelle that serves as the site for biological protein synthesis due to the
presence of translational apparatus,
Made from the complex of RNA and proteins called ribo-nucleoproteins and also called ribozymes
because of catalytic peptidyl-transferase activity that links amino acids together ,
Ribosome from bacteria, archaea and eukaryotes resemble each other and it indicates common origin
in the three domain of life,
The ribosome in mitochondria called mito-ribosomes produced from mitochondrial genes that reflect
the origin from prokaryotes aerobic bacteria by endosymbiotic theory,
A. Claude (1943) observed the basophilic granules rich in nucleic acids Palade in 1955 first isolated it
and Richard B Roberts in 1956 proposed the term ‘ribosome’,
Ribosomal proteins and rRNAs arranged in two sub-units-large and small sub unit of the ribosome;
differences are there between prokaryotic and eukaryotic ribosome,
Prokaryotes have 70S with 50S and 30S ; small sub unit has 16S RNA with 1540 nucleotides bound to
21 proteins and the large sub unit composed of 5S RNA sub unit with 120 nucleotides and 23S RNA
sub unit with 2900 nucleotides and 31 proteins.

24. RIBOSOMES-ROLE IN PROTEIN SYNTHESIS

25. RIBOSOMES-SUB UNITS & FUNCTION
Eukaryotichave80Sribosomewith40Sand60Ssubunit;the40Ssubunithasan18SRNAof1900
nucleotidesand33proteinsandthe60Ssubunitiscomposedof5SRNAof120nucleotides,28S
RNAof4700nucleotidesand5.8SRNAof160nucleotidesand46proteins,
Ribosomeofmitochondriaandchloroplastcontains70Stype,believedtobedescendentsof
prokaryoticorigin,
ThecatalyticactivityofribosomeiscarriedoutbyRNandtheproteinresidueresponsiblefor
stabilizingthestructure,
TheassociationofribosomalsubunitisdependentupontheconcentrationofMg+2ions,thelesser
theconcentrationoftheions,morethechanceofdissociationorviceversa,
Ribosomeinproteinsynthesisappearinchaincalledpolysomes,
Ribosomeareofdiversetypes-Freeribosomepresentanywhereinthecytosol,membranebound
ribosomeassociatedwithendoplasmicreticulumineukaryoticcellcalledrEr;boundribosome
usuallyproduceproteinsthatareusedwithinplasmamembraneorareexpelledfromthecellvia
exocytosis,
FUNCTION:ActsassiteforproteinsynthesisanditisthetranslationalsitewherethemRNA
comprisesaseriesofcodonthatdictatetotheribosomethesequenceofaminoacidsneededtomake
protein.

26. ENDOSYMBIOTIC THEORY
Morethan100theorieshavefiguredoutinthoughtsbetweenprokaryoticandeukaryotes,
Morethan20endosymbiotictheorieslikeIndependenthypothesis,Endogenoustheory,Chimera
hypothesis,Endosymbiotictheoriesetchavebeenpresentedtoexplaintheoriginsofeukaryotesand
theirmitochondria,
EndosymbiotictheorywasfirstarticulatedbyRussianbotanist,KonstantinMarshKowskiin1910and
itwasfirstexplainbyBorisKozo-Polyanskyin1924.
Theroleofenergyandtheenergyconstraintsthatprokaryoticcellorganizationplacedonevolutionary
innovationincellhistoryhascometobearonendosymbiotiictheory.
Onlycellsthatpossessmitochondriahadthebioenergeticsmeanstoattaineukaryoticcellcomplexity,
Itindicatesthetransitionbetweenprokaryotetoeukaryotes,
Theevolutionaryhistoryandbiologyofarchaeaincreasinglycomestobearoneukaryoticorigins.
Moleculardatahaveplayedanimportantroleinsupportingexogenousorigin(fromoutsideofcell)
ratherthanautogenouslyorigin(fromwithinthecell)oforganelles.Recentphylogeneticanalyses
revealthatmanyeukaryoticorganelleandnucleargeneswhoseprokaryoticancestrycanbepinned
downareofbacterialorigin.
Phylogeneticanalysesrevealthatmanyeukaryoticorgnallearandnucleargeneswhoseprokaryotic
ancestrycanbepinneddownareofbacterialorigin.Inthecaseofendosymbiosisonetypeofcell
(symbionts)enteredintoanothertypeofcell(host)throughphagocytosis.

27. ENDOSYMBIOTIC THEORY

28. ENDOSYMBIOTIC THEORY
•Itisthoughtthatlifearoseoneartharoundfourbillionyearsago.Theendosymbiotictheorystatesthat
someoftheorganellesintoday'seukaryoticcellswereonceprokaryoticmicrobes.Inthistheory,the
firsteukaryoticcellwasprobablyanamoeba-likecellthatgotnutrientsbyphagocytosisandcontained
anucleusthatformedwhenapieceofthecytoplasmicmembranepinchedoffaroundthe
chromosomes.Someoftheseamoeba-likeorganismsingestedprokaryoticcellsthatthensurvived
withintheorganismanddevelopedasymbioticrelationship.Mitochondriaformedwhenbacteria
capableofaerobicrespirationwereingested;chloroplastsformedwhenphotosyntheticbacteriawere
ingested.TheyeventuallylosttheircellwallandmuchoftheirDNAbecausetheywerenotofbenefit
withinthehostcell.Mitochondriaandchloroplastscannotgrowoutsidetheirhostcell.
•Evidenceforthisisbasedonthefollowing:
Chloroplastsarethesamesizeasprokaryoticcells,dividebybinaryfission,and,likebacteria,have
Ftsproteinsattheirdivisionplane.Themitochondriaarethesamesizeasprokaryoticcells,divideby
binaryfission,andthemitochondriaofsomeprotistshaveFtsproteinsattheirdivisionplane.
MitochondriaandchloroplastshavetheirownDNAthatiscircular,notlinear.
Mitochondriaandchloroplastshavetheirownribosomethathave30Sand50Ssubunits,not40S
and60S.

29. EVIDENCE IN SUPPORT OF ENDOSYMBIOTIC THEORY
Genomecomparisonindicatetheaerobicbacteriacontributedtothegeneticoriginofmitochondria,
Theoriginofplastidhasbeenstrengthenedbythegenomiccomparisonofcyanobacteriabeing
autotrophicinnature,
Severalenzymesandtransportsystemsofmitochondriaaresimilartothoseofbacteria,
Mostoftheinternalstructureandbiochemistryofplastidsforexamplethepresenceofthylakoidsand
chlorophyllmolecules,areverysimilartothatofcyanobacteria.Phylogeneticestimatesconstructed
withbacteria,plastidsandeukaryoticgenomessuggestthatplastidsaremostcloselyrelatedto
cyanobacteria.
Amembranelipid,cardiolipinisexclusivelyfoundintheinnermembraneofmitochondriaand
bacterialcellmembrane.
Severalmoreprimitiveeukaryoticmicrobes,suchasGiardiaandTrichomonashaveanuclear
membranebutnomitochondria.

30. ENDOSYMBIOTIC THEORY

31. ENDOSYMBIOSIS
Thus,theendosymbiosistheoryofSymbiogenesistheoryexplains-
Anevolutionaryideatoexplaintheoriginofeukaryotesfromprokaryotes,
Severalkeyorganellesofeukaryotesoriginatesassymbiosisbetweenseparatesinglecelledorganism,
Italsoexplainsthedevelopmentofgradualcomplexityofthestructuralandfunctionalunitinthis
contextthroughthepassageofevolution,
Mitochondriaandchloroplastshavebeenderivedfromtheancientprokaryotestoaddresstheneedof
evolutionthroughthechangingenvironmentalconsequences

32. THANKS TO VISIT THE CONTENT
•References:
1.Googleforimages,
2.DifferentopensourcesofinformationofWebPages
3.Biochemistry-Lehninger
4.Biomolecules&CellBiology-ArunchandraSahu,
5.AtextbookofBotany(Vol.II)Ghosh,Bhattacharya,Hait
6.FundamentalsofBiochemistry-Jain,Jain,&Jain,
7.ATextbookofGenetics-AjoyPaul
•DISCLAIMER:
•Thispresentationhasbeenmadetoenrichopensourceoflearningwithoutanyfinancialinterest.The
presenteracknowledgesGoogleforimagesandotheropensourcesofinformationtodevelopthis
PPT.