1

InsidetheCellBIOL222

Ch.7

Overview:TheFundamentalUnitsofLife

•  Allorganismsaremadeofcells

•  Thecellisthesimplestcollec=onofma>er

thatcanlive

•  Cellstructureiscorrelatedtocellularfunc=on

•  Allcellsarerelatedbytheirdescentfromearliercells

Fig.6-2

10 m

1 m

0.1 m

1 cm

1 mm

100 µm

10 µm

1 µm

100 nm

10 nm

1 nm

0.1 nm Atoms

Small molecules

Lipids

Proteins

Ribosomes

Viruses Smallest bacteria

Mitochondrion

Nucleus Most bacteria

Most plant and animal cells

Frog egg

Chicken egg

Length of some nerve and muscle cells

Human height

Una

ided

eye

Ligh

t mic

rosc

ope

Elec

tron

mic

rosc

ope

2

•  Prokaryo=ccells

•  BacteriaandArchaebacteria

•  Eukaryo=ccells

•  Pro=sts,fungi,plants,andanimals

Prokaryo=candEukaryo=cCells

Prokaryo=candEukaryo=cCells

•  Basicfeaturesofallcells:

•  Plasmamembrane

•  Semifluidsubstancecalledcytosol

•  Cytoplasm=spaceinsidecell

•  filledwithcytosol

•  Chromosome(s)

•  Gene=cinfo

•  Ribosomes

•  Proteinsynthesis

•  Prokaryo=ccellscharacterizedby:

•  Nonucleus

•  nucleoidregioninstead

•  DNAinanunboundarea

•  Nomembranousorganelles

•  Ribosomesonly

•  Notmembranebound

•  Cytoplasm

•  enclosedbytheplasmamembrane

Prokaryo=cCells

Fimbriae

Nucleoid

Ribosomes

Plasma membrane

Cell wall

Capsule

Flagella

Bacterial chromosome

(a) A typical rod-shaped bacterium

(b)A thin section through the bacterium Bacillus coagulans (TEM)

0.5 µm

3

•  Eukaryo=ccellscharacterizedby

having:

•  nucleus

•  enclosesDNA

•  boundedbyadouble

membranousenvelope

•  Manymembranousorganelles

•  Eukaryota

•  muchlargerthanprokaryo=c

cells

•  10x-100xonaverage

Eukaryo=cCells

•  plasmamembrane

•  Selec=velypermeable

•  allowssufficientpassageofoxygen,nutrients,andwaste

toservicethevolumeofeverycell

•  Phospholipidbilayer

•  amphipathic

•  fluidmosaic

CellMembrane

•  Limitstothesizeofcells

•  Diffusioncanonlyworksofar

•  efficiencydeclineswith

distance

•  Surfaceareatovolumera=oofacellis

cri=cal

•  Asthesurfaceareaincreasesbya

factorofn2,thevolumeincreases

byafactorofn3

•  Smallcellshaveagreatersurface

arearela=vetovolume

CellMembrane

Surface area increases while total volume remains constant

5

11

6 150 750

125 1251

6 61.2

Total surface area [Sum of the surface areas (height × width) of all boxes sides × number of boxes]

Total volume [height × width × length × number of boxes]

Surface-to-volume (S-to-V) ratio [surface area ÷ volume]

4

APanoramicViewoftheEukaryo=cCell•  Internalmembranes

•  Par==onthecellinto

organelles

•  Samematerialand

construc=on

•  ascellmembrane

•  Plantandanimalcells

•  havemostofthesame

organelles

ENDOPLASMIC RETICULUM (ER)

Smooth ERRough ERFlagellum

Centrosome

CYTOSKELETON:Microfilaments

Intermediate filaments

Microtubules

Microvilli

Peroxisome

MitochondrionLysosome

Golgi apparatus

Ribosomes

Plasma membrane

Nuclear envelope

Nucleolus

Chromatin

NUCLEUS

NUCLEUSNuclear envelopeNucleolusChromatin

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

Ribosomes

Central vacuole

MicrofilamentsIntermediate filamentsMicrotubules

CYTO- SKELETON

Chloroplast

PlasmodesmataWall of adjacent cell

Cell wall

Plasma membrane

PeroxisomeMitochondrion

Golgi apparatus

Nucleus•  Nucleus

•  containsmostofthecell’sgenesandisusuallythemostconspicuous(largest)organelle

•  Mitochondriaand/orchloroplastsalsohavetheirownDNA

•  mtDNA,ptDNA

•  Nuclearenvelope

•  enclosesthenucleus,separa=ngitfromthecytoplasm

•  doublemembrane;eachmembraneconsistsofaphospholipidbilayer

•  Studdedwithnuclearpores

ENDOPLASMIC RETICULUM (ER)

Smooth ERRough ERFlagellum

Centrosome

CYTOSKELETON:

Microfilaments

Intermediate filaments

Microtubules

Microvilli

Peroxisome

MitochondrionLysosome

Golgi apparatus

Ribosomes

Plasma membrane

Nuclear envelope

Nucleolus

Chromatin

NUCLEUS

Fig.6-10

NucleolusNucleus

Rough ER

Nuclear lamina (TEM)

Close-up of nuclear envelope

1 µm

1 µm

0.25 µm

Ribosome

Pore complex

Nuclear pore

Outer membraneInner membraneNuclear envelope:

Chromatin

Surface of nuclear envelope

Pore complexes (TEM)

5

•  NuclearPores

•  regulatetheentry

andexitofmolecules

fromthenucleus

•  Nuclearlamina

•  maintainsshapeofthe

nucleus

•  composedofprotein

•  Intermediatefilaments

•  Similartocytoskeleton

Nucleus

NucleolusNucleus

Rough ER

Nuclear lamina (TEM)

Close-up of nuclear envelope

1 µm

1 µm

0.25 µm

Ribosome

Pore complex

Nuclear pore

Outer membraneInner membraneNuclear envelope:

Chromatin

Surface of nuclear envelope

Pore complexes (TEM)

•  Chroma=n

•  DiffuseformofGene=cmaterialmadeofDNAandproteins

•  Chromosomes

•  Condensedchroma=n

•  Onlyduringcelldivision

•  Nucleolus

•  siteofribosomalRNA(rRNA)synthesis

•  locatedwithinthenucleus

•  Seenaslargedarkspot

Nucleus

Ribosomes

•  Ribosomes

•  par=clesmadeof

ribosomalRNAandprotein

•  Onlyorganellewithoutamembraneenclosure

•  carryoutproteinsynthesisintwoloca=ons:

•  Inthecytosol(freeribosomes)

•  Ontheoutsideoftheendoplasmic

re=culumorthenuclearenvelope

(boundribosomes)

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Fig.6-11

Cytosol

Endoplasmic reticulum (ER)

Free ribosomes

Bound ribosomes

Large subunit

Small subunit

Diagram of a ribosomeTEM showing ER and ribosomes

0.5 µm

EndomembraneSystem•  Componentsoftheendomembrane

system:

•  Nuclearenvelope

•  Endoplasmicre=culum

•  Golgiapparatus

•  Lysosomes

•  Vacuoles

•  Plasmamembrane

•  Thesecomponentsareeither

con=nuousorconnectedviatransfer

byvesicles

Biosynthesis:EndoplasmicRe=culum

•  Endoplasmicre=culum(ER)

•  accountsformorethanhalfofthetotalmembraneinmany

eukaryo=ccells

•  con=nuouswiththenuclearenvelope

•  TworegionsofER:

•  SmoothER

•  Noribosomes

•  RoughER

•  Ribosomesa>ached

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Fig.6-12

Smooth ER

Rough ER Nuclear envelope

Transitional ER

Rough ERSmooth ERTransport vesicle

RibosomesCisternaeER lumen

200 nm

SmoothEndoplasmicRe=culum•  ThesmoothER

•  Synthesizeslipids

•  Phospholipids

•  Steroids

•  Metabolizescarbs

•  Glycogenolysis/

gluconeogenesis

•  Detoxifiespoisons

•  Storescalcium

•  Sarcoplasmicre=culum

RoughEndoplasmicRe=culum

•  RoughER

•  Ribosomesa>ached

•  Sitesofmembraneand

secretoryproteinsynthesis

•  Transportvesicles

•  Proteinssurroundedbymembranes

•  BudfromRERmembrane

•  Isamembranemanufacturingandassemblyfactoryforthecell

•  AlongwithSER

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TheGolgiApparatus

cis face (“receiving” side of Golgi apparatus) Cisternae

trans face (“shipping” side of Golgi apparatus)

TEM of Golgi apparatus

0.1 µm

•  Golgiapparatus

•  Cisternae

•  fla>enedmembranoussacs

•  Func=ons:

•  ModifiesproductsoftheER

•  Manufacturessome

polysaccharides(pec=n)

•  Sortsandpackages

materialsintotransport

vesicles

Lysosomes

•  Lysosome

•  membranoussacofhydroly=cenzymes

•  digestmacromolecules

•  hydrolyzeproteins,fats,polysaccharides,andnucleicacids

•  Phagocytosis

•  Onecellengulfinganother

•  formsafoodvacuole

•  fuseswithlysosome

•  Autophagy

•  Lysosomesuseenzymes

•  torecyclethecell’sownorganelles

andmacromolecules

Lysosomes

9

Fig.6-14

Nucleus 1 µm

LysosomeDigestive enzymes

Lysosome

Plasma membrane

Food vacuole

(a) Phagocytosis

Digestion

(b) Autophagy

Peroxisome

Vesicle

Lysosome

Mitochondrion

Peroxisome fragment

Mitochondrion fragment

Vesicle containing two damaged organelles 1 µm

Digestion

•  Aplantcellorfungalcellmayhaveoneor

severalvacuoles

•  Foodvacuoles

•  formedbyphagocytosis

•  Contrac=levacuoles

•  foundinmanyfreshwaterpro=sts,

pumpexcesswateroutofcells

•  Centralvacuoles

•  foundinmanymatureplantcells,

holdorganiccompoundsandwater

Vacuoles

Central vacuole

Cytosol

Central vacuole

Nucleus

Cell wall

Chloroplast

5 µm

MitochondriaandChloroplasts

•  Mitochondria

–  sitesofcellularrespira=on

–  Inplantstoo

•  Chloroplasts

•  inplantsandalgaeonly

•  sitesofphotosynthesis

•  Bothchangeenergyfromoneform

toanother

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•  Mitochondriaandchloroplasts

•  Arenotpartoftheendomembranesystem

•  Haveadoublemembrane

•  Haveproteinsmadebyfreeribosomes

•  ContaintheirownDNA?!

•  Endosymbionttheory

MitochondriaandChloroplasts

•  hMp://www.sciencedaily.com/releases/2011/07/110725190046.htm

•  hMp://www.nature.com/srep/2011/110614/srep00013/full/srep00013.html

Mitochondria•  Mitochondria

•  innearlyalleukaryo=ccells

•  Allhaveevolu=onarydescendants

ofmitochondria

•  Cristae

•  Foldsofinnermembranetoincreasesurfacearea

•  innermembrane

•  createstwocompartments:

•  intermembranespace

•  ForH+gradientofelectrontransportchain

•  mitochondrialmatrix

•  ForKrebsCycle

Fig.6-17

Free ribosomes in the mitochondrial matrix

Intermembrane spaceOuter membrane

Inner membraneCristae

Matrix

0.1 µm

11

•  Chloroplaststructureincludes:

•  Thylakoids

•  membranoussacs,stackedtoformagranum

•  Stroma

•  internalfluid

Chloroplasts

Ribosomes

Thylakoid

Stroma

Granum

Inner and outer membranes

1 µm

Peroxisomes:Oxida=on•  Peroxisomes

•  Specializedmetaboliccompartments

•  Boundbyasinglemembrane

•  Oxygenusedtobreakdowndifferenttypesofmolecules

•  H2O2by-productconvertedtowater

Cytoskeleton•  Cytoskeleton

•  networkofproteinfibersextending

throughoutthecytoplasm

•  organizesthecell’sstructuresand

ac=vi=es

•  anchorsmanyorganelles

•  composedofthreetypesofmolecular

structures:

•  Microtubules

•  Microfilaments

•  Intermediatefilaments

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Cytoskeleton:Support,Mo=lity,andRegula=on•  Cytoskeleton

•  supportthecellandmaintainitsshape

•  motorproteins

•  producemo=lity

•  vesiclescantravelalong“monorails”

•  providedbythecytoskeleton

•  Recentevidencesuggests

•  cytoskeletonmayhelpregulatebiochemical

ac=vi=es

PLAY

ComponentsoftheCytoskeleton

•  Threemaintypesoffibersmakeup

thecytoskeleton:

•  Microtubules

•  thickest

•  Intermediatefilaments

•  Mediumsizeddiameter

•  Microfilaments

•  Thinnest

•  alsocalledac=nfilaments

•  Centrosomes

•  Structurenearnucleusfromwhere

microtubulesgrow

•  a“microtubule-organizingcenter”

•  Inanimalcells

•  Consistsoftwocentrioles

•  Centrioles

•  Pairedstructuresconsis=ngofnine

tripletsofmicrotubulesarranged

inaring

MicrotubulesandCellDivision

Centrosome

Microtubule

Centrioles0.25 µm

Longitudinal section of one centriole

Microtubules Cross section of the other centriole

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ExtracellularMatrix

•  Mostcellssynthesizeandsecrete

materials

•  thatareexternaltotheplasma

membrane

•  Theseextracellularstructuresinclude:

•  Cellwallsofplants

•  Theextracellularmatrix(ECM)of

animalcells

•  Intercellularjunc=ons

CellWallsofPlants•  cellwall

•  extracellularstructure

•  dis=nguishesplantcellsfromanimalcells

•  madeofcellulosefibers

•  embeddedinotherpolysaccharidesandprotein

•  protectstheplantcell,maintainsitsshape,andpreventsexcessiveuptakeofwater

•  Prokaryotes,fungi,andafewpro=stsalsohavecellwalls

•  Bacteria-pep=doglycan

•  Fungi-chi=n

TheExtracellularMatrix(ECM)ofAnimalCells

•  Extracellularmatrix(ECM)

•  AnimalcellslackcellwallsbutarecoveredbyECM

•  madeupofglycoproteins

•  Collagen

•  Proteoglycans

•  fibronec=n

•  Integrins

•  ReceptorproteinsintheplasmamembranetowhichECMproteinsbind

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•  Func=onsoftheECM:

•  Support

•  Anchorageandsepara=onofdifferent=ssues

•  Adhesion

•  Bindcellstogetherwithin=ssues

•  Movement

•  Guideforcellmigra=oninembryonicdevelopment

•  Regula=on

•  Propaga=onofexternals=mulitonucleus

ExtracellularMatrix

Fig.6-30

EXTRACELLULAR FLUIDCollagen

Fibronectin

Plasma membrane

Micro- filaments

CYTOPLASM

Integrins

Proteoglycan complex

Polysaccharide molecule

Carbo- hydrates

Core protein

Proteoglycan molecule

Proteoglycan complex

IntercellularJunc=ons

•  Intercellularjunc=ons

•  facilitatecontactbetweenneighboringcellsin=ssues,organs,ororgan

systems

•  adhere,interact,andcommunicatethroughdirectphysicalcontact

•  Types

•  Plasmodesmata

•  Plantsonly

•  Tightjunc=ons

•  Desmosomes

•  Gapjunc=ons

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PlasmodesmatainPlantCells

•  Plasmodesmata

•  channelsthatperforateplantcellwalls

•  waterandsmallsolutes

•  some=mesproteinsandRNA

•  canpassfromcelltocell

•  Plasmamembranecon=nuous

•  fromonecelltoanother

Fig.6-31

Interior of cell

Interior of cell

0.5 µm Plasmodesmata Plasma membranes

Cell walls

TightJunc=ons,Desmosomes,andGapJunc=ons•  =ghtjunc=ons

•  Leak-proofbarrier

•  Plasmamembranessqueezedtogether

•  Diges=vesystem

•  Desmosomes

•  anchoringjunc=onsfastencellstogetherintostrongsheets

•  rivets

•  Gapjunc=ons

•  communica=ngjunc=onsprovidecytoplasmicchannelsbetweenadjacentcells

Tight junctions prevent fluid from moving across a layer of cells

Tight junction

Intermediate filaments

Desmosome

Gap junctions

Extracellular matrixSpace

between cells

Plasma membranes of adjacent cells

16

Youshouldnowbeableto:1.  Dis=nguishbetweenthefollowingpairsofterms:magnifica=onand

resolu=on;prokaryo=candeukaryo=ccell;freeandboundribosomes;smoothandroughER

2.  Describethestructureandfunc=onofthecomponentsoftheendomembranesystem

3.  Brieflyexplaintheroleofmitochondria,chloroplasts,andperoxisomes

4.  Describethefunc=onsofthecytoskeleton

5.  Comparethestructureandfunc=onsofmicrotubules,microfilaments,andintermediatefilaments

6.  Explainhowtheultrastructureofciliaandflagellarelatetotheirfunc=ons

7.  Describethestructureofaplantcellwall

8.  Describethestructureandrolesoftheextracellularmatrixinanimalcells

9.  Describefourdifferentintercellularjunc=ons