1

•  Phagocytosis

•  Onecellengulfinganother

•  formsafoodvacuole

•  fuseswithlysosome

•  Autophagy

•  Lysosomesuseenzymes

•  torecyclethecell’sownorganelles

andmacromolecules

Lysosomes

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

•  Contrac9levacuoles

•  foundinmanyfreshwaterproBsts,

pumpexcesswateroutofcells

•  Centralvacuoles

•  foundinmanymatureplantcells,

holdorganiccompoundsandwater

Vacuoles

Central vacuole

Cytosol

Central vacuole

Nucleus

Cell wall

Chloroplast

5 µm

2

MitochondriaandChloroplasts

•  Mitochondria

–  sitesofcellularrespiraBon

–  Inplantstoo

•  Chloroplasts

•  inplantsandalgaeonly

•  sitesofphotosynthesis

•  Bothchangeenergyfromoneform

toanother

•  Mitochondriaandchloroplasts

•  Arenotpartoftheendomembranesystem

•  Haveadoublemembrane

•  Haveproteinsmadebyfreeribosomes

•  ContaintheirownDNA?!

•  Endosymbionttheory

MitochondriaandChloroplasts

•  h<p://www.sciencedaily.com/releases/2011/07/110725190046.htm

•  h<p://www.nature.com/srep/2011/110614/srep00013/full/srep00013.html

Mitochondria•  Mitochondria

•  innearlyalleukaryoBccells

•  AllhaveevoluBonarydescendants

ofmitochondria

•  Cristae

•  Foldsofinnermembranetoincreasesurfacearea

•  innermembrane

•  createstwocompartments:

•  intermembranespace

•  ForH+gradientofelectrontransportchain

•  mitochondrialmatrix

•  ForKrebsCycle

3

Fig.6-17

Free ribosomes in the mitochondrial matrix

Intermembrane spaceOuter membrane

Inner membraneCristae

Matrix

0.1 µm

•  Chloroplaststructureincludes:

•  Thylakoids

•  membranoussacs,stackedtoformagranum

•  Stroma

•  internalfluid

Chloroplasts

Ribosomes

Thylakoid

Stroma

Granum

Inner and outer membranes

1 µm

Peroxisomes:Oxida9on•  Peroxisomes

•  Specializedmetaboliccompartments

•  Boundbyasinglemembrane

•  Oxygenusedtobreakdowndifferenttypesofmolecules

•  H2O2by-productconvertedtowater

4

Cytoskeleton•  Cytoskeleton

•  networkofproteinfibersextending

throughoutthecytoplasm

•  organizesthecell’sstructuresand

acBviBes

•  anchorsmanyorganelles

•  composedofthreetypesofmolecular

structures:

•  Microtubules

•  Microfilaments

•  Intermediatefilaments

Cytoskeleton:Support,Mo9lity,andRegula9on•  Cytoskeleton

•  supportthecellandmaintainitsshape

•  motorproteins

•  producemoBlity

•  vesiclescantravelalong“monorails”

•  providedbythecytoskeleton

•  Recentevidencesuggests

•  cytoskeletonmayhelpregulatebiochemical

acBviBes

PLAY

ComponentsoftheCytoskeleton

•  Threemaintypesoffibersmakeup

thecytoskeleton:

•  Microtubules

•  thickest

•  Intermediatefilaments

•  Mediumsizeddiameter

•  Microfilaments

•  Thinnest

•  alsocalledacBnfilaments

5

•  Centrosomes

•  Structurenearnucleusfromwhere

microtubulesgrow

•  a“microtubule-organizingcenter”

•  Inanimalcells

•  Consistsoftwocentrioles

•  Centrioles

•  PairedstructuresconsisBngofnine

tripletsofmicrotubulesarranged

inaring

MicrotubulesandCellDivision

Centrosome

Microtubule

Centrioles0.25 µm

Longitudinal section of one centriole

Microtubules Cross section of the other centriole

ExtracellularMatrix

•  Mostcellssynthesizeandsecrete

materials

•  thatareexternaltotheplasma

membrane

•  Theseextracellularstructuresinclude:

•  Cellwallsofplants

•  Theextracellularmatrix(ECM)of

animalcells

•  IntercellularjuncBons

CellWallsofPlants•  cellwall

•  extracellularstructure

•  disBnguishesplantcellsfromanimalcells

•  madeofcellulosefibers

•  embeddedinotherpolysaccharidesandprotein

•  protectstheplantcell,maintainsitsshape,andpreventsexcessiveuptakeofwater

•  Prokaryotes,fungi,andafewproBstsalsohavecellwalls

•  Bacteria-pepBdoglycan

•  Fungi-chiBn

6

TheExtracellularMatrix(ECM)ofAnimalCells

•  Extracellularmatrix(ECM)

•  AnimalcellslackcellwallsbutarecoveredbyECM

•  madeupofglycoproteins

•  Collagen

•  Proteoglycans

•  fibronec9n

•  Integrins

•  ReceptorproteinsintheplasmamembranetowhichECMproteinsbind

•  FuncBonsoftheECM:

•  Support

•  AnchorageandseparaBonofdifferentBssues

•  Adhesion

•  BindcellstogetherwithinBssues

•  Movement

•  GuideforcellmigraBoninembryonicdevelopment

•  RegulaBon

•  PropagaBonofexternalsBmulitonucleus

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

7

IntercellularJunc9ons

•  IntercellularjuncBons

•  facilitatecontactbetweenneighboringcellsinBssues,organs,ororgan

systems

•  adhere,interact,andcommunicatethroughdirectphysicalcontact

•  Types

•  Plasmodesmata

•  Plantsonly

•  TightjuncBons

•  Desmosomes

•  GapjuncBons

PlasmodesmatainPlantCells

•  Plasmodesmata

•  channelsthatperforateplantcellwalls

•  waterandsmallsolutes

•  someBmesproteinsandRNA

•  canpassfromcelltocell

•  PlasmamembraneconBnuous

•  fromonecelltoanother

Fig.6-31

Interior of cell

Interior of cell

0.5 µm Plasmodesmata Plasma membranes

Cell walls

8

TightJunc9ons,Desmosomes,andGapJunc9ons•  9ghtjunc9ons

•  Leak-proofbarrier

•  Plasmamembranessqueezedtogether

•  DigesBvesystem

•  Desmosomes

•  anchoringjuncBonsfastencellstogetherintostrongsheets

•  rivets

•  Gapjunc9ons

•  communicaBngjuncBonsprovidecytoplasmicchannelsbetweenadjacentcells

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

Youshouldnowbeableto:1.  DisBnguishbetweenthefollowingpairsofterms:magnificaBonand

resoluBon;prokaryoBcandeukaryoBccell;freeandboundribosomes;smoothandroughER

2.  DescribethestructureandfuncBonofthecomponentsoftheendomembranesystem

3.  Brieflyexplaintheroleofmitochondria,chloroplasts,andperoxisomes

4.  DescribethefuncBonsofthecytoskeleton

5.  ComparethestructureandfuncBonsofmicrotubules,microfilaments,andintermediatefilaments

6.  ExplainhowtheultrastructureofciliaandflagellarelatetotheirfuncBons

7.  Describethestructureofaplantcellwall

8.  Describethestructureandrolesoftheextracellularmatrixinanimalcells

9.  DescribefourdifferentintercellularjuncBons