Cell Structure & Cell Structure & FunctionFunction

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Microscope HistoryMicroscope HistoryHooke’s (1665) Hooke’s (1665)

drawings of drawings of corkcork

Early light Early light microscopemicroscope

Electron Electron microscopemicroscope

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Microscopic ImagesMicroscopic Images

ParameciumParamecium

LightLightMicrographMicrograph Scanning ElectronScanning Electron

Micrograph Micrograph

Transmission ElectronTransmission Electron Micrograph Micrograph

Scanning ElectronScanning Electron Micrograph Micrograph

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Cell TheoryCell Theory

All living things are composed of one or All living things are composed of one or more cellsmore cells

Cells are:Cells are:

• Basic unit of structureBasic unit of structure

• Basic unit of functionBasic unit of function

All cells come from preexisting cellsAll cells come from preexisting cells

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Basic Cell StructureBasic Cell Structure

All cells possess a plasma membrane, All cells possess a plasma membrane, cytoplasm, genetic materialcytoplasm, genetic material

Plasma membrane has phospholipid Plasma membrane has phospholipid bilayer, embedded glycoproteinsbilayer, embedded glycoproteins• Isolates cytoplasm from environmentIsolates cytoplasm from environment

• Regulates molecular movement into and out Regulates molecular movement into and out of cellof cell

• Interacts with other cells/environmentInteracts with other cells/environment

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AmoebaAmoeba

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Relative SizesRelative Sizes

100 m

10 m

1 m

10 cm

1 cm

1 mm

100 m

10 m

1 m

100 nm

10 nm

1 nm

0.1 nm

Elec

tron

Mic

rosc

ope

Ligh

t Mic

rosc

ope

Una

ided

eye

Spec

ial

E.M

.

Eukaryotic CellsEukaryotic Cells

VirusVirus

ProteinsProteins

AtomsAtoms

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Cell TypesCell Types

Prokaryotic:Prokaryotic:• Smaller, 1—5 µmSmaller, 1—5 µm• No organellesNo organelles• No nucleusNo nucleus• DNA in circular loop DNA in circular loop

Eukaryotic:Eukaryotic:• Larger, 8—100 µmLarger, 8—100 µm• Membranous organellesMembranous organelles• NucleusNucleus• DNA in linear chromosomesDNA in linear chromosomes

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Generalized ProkaryoteGeneralized Prokaryote

CapsuleCapsule

Cell WallCell WallPlasmaPlasmaMembraneMembrane

CytosolCytosol

Nucleoid DNANucleoid DNA

FlagellumFlagellum

Plasmid DNAPlasmid DNA

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Bacilli (1000x)Bacilli (1000x)

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Eukaryotic CellsEukaryotic Cells

Genetic material - DNA, found in the nucleusGenetic material - DNA, found in the nucleus

Cytoplasm – everything else within the plasma Cytoplasm – everything else within the plasma membranemembrane

• Cytosol (the fluid part)Cytosol (the fluid part)

– WaterWater

– SaltsSalts

– Organic monomers and polymersOrganic monomers and polymers

• OrganellesOrganelles

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Generalized Cell Generalized Cell AnimalAnimal

CellCellAnimalAnimal

CellCell

PlantPlantCellCell

PlantPlantCellCell

NucleusNucleus

GolgiGolgi

MitochondriaMitochondria

EndoplasmicEndoplasmicReticulumReticulum

CentriolesCentrioles ChloroplastsChloroplasts

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AnimalAnimalCellCell

AnimalAnimalCellCell

PlantPlantCellCell

PlantPlantCellCell

Generalized CellGeneralized Cell

NucleolusNucleolus

RibosomesRibosomes

Central VacuoleCentral Vacuole

Smooth E.R.Smooth E.R. Cell WallCell Wall

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1.1.Control StructuresControl Structuresa. Nucleusa. Nucleus

a. Nucleusa. Nucleus Structure:Structure:

• about 5 about 5 m in diameterm in diameter• bound within the nuclear envelopebound within the nuclear envelope• contains DNA complex (chromatin)contains DNA complex (chromatin)

Function:Function:• genes within DNA include instructions genes within DNA include instructions

for production of proteins to control for production of proteins to control metabolism and other cell functionsmetabolism and other cell functions

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The NucleusThe NucleusNucleolusNucleolus

PoresPores

Chromatin ThreadsChromatin Threads(Chromosomes)(Chromosomes) NuclearNuclear

EnvelopeEnvelope

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ChromosomesChromosomes

NucleoliNucleoli

NucleusNucleus

Cell WallCell Wall

ChromosomesChromosomes

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1.1.Control Structures Control Structures b. Nuclear Envelopeb. Nuclear Envelope

Structure:Structure:• double membrane (two bilipid layers)double membrane (two bilipid layers)• nuclear lamina (protein network)nuclear lamina (protein network)

– between membrane layers (20-40 nm)between membrane layers (20-40 nm)• perforated by pores (100 nm diameter)perforated by pores (100 nm diameter)

Function:Function:• stabilizes shape stabilizes shape • part of endomembrane systempart of endomembrane system

(transport)(transport)

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1.1.Control StructuresControl Structuresc. Nucleolusc. Nucleolus

Structure:Structure:• spherical region in nucleusspherical region in nucleus• composed of RNAcomposed of RNA

Function:Function:• packages ribosome subunitspackages ribosome subunits

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1.1.Control StructuresControl Structures d. Ribosomesd. Ribosomes

Structure:Structure:• complexes of RNA and proteinscomplexes of RNA and proteins• composed of two subunitscomposed of two subunits

Function: (as either free or bound)Function: (as either free or bound)• free ribososmes free ribososmes make proteinsmake proteins that that

function in the cytoplasmfunction in the cytoplasm• bound (to ER) ribosomes bound (to ER) ribosomes make proteinsmake proteins

destined for membranes or for exportdestined for membranes or for export

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RibosomesRibosomes

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2. Endomembrane System2. Endomembrane Systema. ER (Endoplasmic Reticulum)a. ER (Endoplasmic Reticulum)

Structure:Structure:• continuous with outer membrane of continuous with outer membrane of nuclear envelopenuclear envelope• folded membrane networkfolded membrane network

Function: (as either smooth or rough)Function: (as either smooth or rough)• rough ER (studded with ribosomes) makes rough ER (studded with ribosomes) makes

proteins and membranes (grow in place)proteins and membranes (grow in place)• smooth ER makes lipids, phospholipids, smooth ER makes lipids, phospholipids,

and steroidsand steroids

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Rough vs. Smooth ER: TEMRough vs. Smooth ER: TEM

Rough ERRough ERRough ERRough ER

Smooth ERSmooth ERSmooth ERSmooth ER

RibosomesRibosomes

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The Endoplasmic ReticulumThe Endoplasmic Reticulum

RibosomesRibosomes

UnitUnitMembraneMembrane

VesiclesVesiclesformingforming

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2. Endomembrane System2. Endomembrane System b. Golgi Apparatusb. Golgi Apparatus

Structure:Structure:• stack of flattened membrane sacsstack of flattened membrane sacs• two faces two faces

– ciscis “receiving” “receiving” – transtrans “shipping” “shipping”

Function:Function:• receives molecules from ER for processingreceives molecules from ER for processing• molecules are modified and packaged molecules are modified and packaged

as they are passed from sac to sacas they are passed from sac to sac

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The Golgi ComplexThe Golgi ComplexMaterial Material

ReceivedReceivedFrom ERFrom ER

Material DestinedMaterial Destinedfor Exportfor Export

TEMTEM

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2. Endomembrane System2. Endomembrane System c. Lysosomesc. Lysosomes

Structure:Structure:

• Small membrane sacs made by GolgiSmall membrane sacs made by Golgi

• Vesicles contain hydrolytic enzymesVesicles contain hydrolytic enzymes

Function:Function:

• Digest material engulfed by cellDigest material engulfed by cell

• Digest and recycle damaged organellesDigest and recycle damaged organelles

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2. Endomembrane System2. Endomembrane System d. Central Vacuolesd. Central Vacuoles

Structure:Structure:• Large, water-filled spaces (cell sap)Large, water-filled spaces (cell sap)

• Can take up over 90% of cell volumeCan take up over 90% of cell volume

• Enclosed by tonoplast (single membrane)Enclosed by tonoplast (single membrane)

Function:Function:• Storage of pigments (red/blue), acids, salts, Storage of pigments (red/blue), acids, salts,

wasteswastes

• Maintain cell pressure (turgor pressure)Maintain cell pressure (turgor pressure)

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Plant Wilting &Plant Wilting &the Central Vacuolethe Central Vacuole

VacuoleVacuole(tonoplast)(tonoplast) Cell WallCell Wall

Cyt

opla

sm

Cyt

opla

sm

NormalNormalPlant CellPlant Cell

In SaltIn SaltWaterWater

Space between Cell WallSpace between Cell Walland Cell Membraneand Cell Membrane

Normal

In Salt Water

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2. Endomembrane System2. Endomembrane System e. Contractile Vacuolee. Contractile Vacuole

Structure: Structure: • Membrane-bounded sac Membrane-bounded sac

• Connected to canals radiating through cytoplasm Connected to canals radiating through cytoplasm

Function:Function:• Control water balance in hypotonic environment.Control water balance in hypotonic environment.

• Fills with water entering cytoplasm (due to osmosis).Fills with water entering cytoplasm (due to osmosis).

• Pumps water out of the cell by contractingPumps water out of the cell by contracting

• Requires ATPRequires ATP

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Contractile VacuolesContractile Vacuoles

1111

2222

Paramecium sp.

Expelling WaterExpelling Waterto Outsideto Outside

ExpandedExpandedwith Waterwith Water

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The Endomembrane SystemThe Endomembrane System

LysosomeLysosome

Vessicle forVessicle forExportExport

GolgiGolgiEndoplasmicEndoplasmic

ReticulumReticulum

Vessicle Vessicle

Food Food VacuoleVacuole

Food Food VacuoleVacuole

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3. Other Membranous Organelles3. Other Membranous Organellesa. Plastidsa. Plastids

• a group of plant and algal membrane-a group of plant and algal membrane-bound organellesbound organelles

i.i. Chromoplasts (Chromoplasts (chromo = colorchromo = color))• pigment containing plastidspigment containing plastids

• fruits, flowers, autumn leavesfruits, flowers, autumn leaves

ii. ii. Amyloplasts (Amyloplasts (amylo = starchamylo = starch))• colorless plastids that store starch colorless plastids that store starch

• found in roots and tubersfound in roots and tubers

iii.iii. Chloroplasts (Chloroplasts (chloro = greenchloro = green))

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The AmyloplastThe Amyloplast

DoubleDoubleBilipidBilipid

MembraneMembrane

StarchStarchGranulesGranules

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a. Plastids a. Plastids iii. Chloroplastiii. Chloroplast

Structure:Structure:• Contain chlorophyllContain chlorophyll• Bounded by a double membraneBounded by a double membrane• Thylakoid staked into granaThylakoid staked into grana• Stroma (viscous fluid) outside thylakoidsStroma (viscous fluid) outside thylakoids• Contain ribosomes and some DNAContain ribosomes and some DNA

Function:Function:• Site of PhotosynthesisSite of Photosynthesis

– Captures light energyCaptures light energy– Produces carbohydrate from COProduces carbohydrate from CO22 and H and H22OO

• Self-replicating (semi-autonomous)Self-replicating (semi-autonomous)

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The ChloroplastThe Chloroplast

ThylakoidsThylakoids

OuterOuterMembraneMembrane

Intermembrane Intermembrane SpaceSpace

GranumGranum

StromaStroma

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Elodea (400x)Elodea (400x)

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3. Other Membranous Organelles3. Other Membranous Organelles b. Mitochondriab. Mitochondria

Structure: Structure: • Bounded by double membraneBounded by double membrane• Inner membrane folded into cristaeInner membrane folded into cristae• Mitochondrial matrix – within cristaeMitochondrial matrix – within cristae• Contain own DNA and ribosomes Contain own DNA and ribosomes

Function:Function:• Site of cellular respirationSite of cellular respiration

– convert energy stored in food into ATPconvert energy stored in food into ATP– ““powerhouse” of the cellpowerhouse” of the cell– number varies, but related to cell’s metabolic activitynumber varies, but related to cell’s metabolic activity

• Self-replicating (semi-autonomous)Self-replicating (semi-autonomous)

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The MitochondrionThe Mitochondrion

CristaeCristaeMatrixMatrix

OuterOuterMembraneMembrane

InnerInnerMembraneMembrane

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4. The Cytoskeleton4. The Cytoskeleton

Protein fibersProtein fibers• Cell shape; networks of intermediate Cell shape; networks of intermediate

filamentsfilaments• Cell movement; microfilaments & Cell movement; microfilaments &

microtubulesmicrotubules– Amoeboid movementAmoeboid movement– Muscle contractionMuscle contraction– Cell migration during developmentCell migration during development

• Organelle movement & suspensionOrganelle movement & suspension– Cyclosis; pathways for vesicle migrationCyclosis; pathways for vesicle migration

• Cell divisionCell division

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The CytoskeletonThe Cytoskeleton

MicrotubuleMicrotubule

MicrofilamentsMicrofilaments

IntermediateIntermediateFilamentsFilaments

Actin monomersActin monomers

Tubulin dimerTubulin dimer

EndoplasmicReticulum

Mitochondrion

PlasmaMembrane

Fibrous subunitsFibrous subunits

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4. The Cytoskeleton4. The Cytoskeleton a. Centriolesa. Centrioles

Structure:Structure:• Pair of cylindrical structuresPair of cylindrical structures

– 9 sets of triplet 9 sets of triplet microtubulesmicrotubules– Arranged in a ring Arranged in a ring

• ~ 50 nm at right angles~ 50 nm at right angles

Function:Function:• Replicate during cell divisionReplicate during cell division

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Centriole x.s.Centriole x.s.

T.E.M.

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4. The Cytoskeleton4. The Cytoskeleton b. Cilia and Flagellab. Cilia and Flagella

Structure:Structure:• Tubular extensions of plasma membraneTubular extensions of plasma membrane• Anchored by basal body (like centriole)Anchored by basal body (like centriole)• ““9+2” arrangement9+2” arrangement

– 9 doublet 9 doublet microtubulesmicrotubules in complex in complex– 2 single 2 single microtubulesmicrotubules in center in center

Function:Function:• Movement of fluid, or locomotionMovement of fluid, or locomotion

– Cilia: numerous, paddle-like, synchronizedCilia: numerous, paddle-like, synchronized– Flagella: longer, fewer, more whip-likeFlagella: longer, fewer, more whip-like

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Cilia & FlagellaCilia & Flagellax.s.x.s.

CellCellMembraneMembrane

ShaftShaft

BaseBase(a Centriole)(a Centriole)

T.E.M.

Paramecium

Euglena

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Flagellum PartsFlagellum PartsShaft, l.s.Shaft, l.s.

Shaft,Shaft,x.s.x.s. Microtubule Microtubule DoubletsDoublets

Cell MembraneCell Membrane

Dynein ArmsDynein Arms

Central Central SingletsSinglets

Microtubule Microtubule TripletsTriplets

Basal BodyBasal BodyBasal Body,Basal Body,

x.s.x.s.

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Flagella MovementFlagella Movement

Scanning E.M.Scanning E.M.of sperm on eggof sperm on eggScanning E.M.Scanning E.M.

of sperm on eggof sperm on egg

Corkscrew Movement(Pulls)

Whipping Movement(Pushes)

Water Water

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Movement of CiliaMovement of CiliaActive Stroke Recovery Stroke

Water

Cilia on Cilia on trachea trachea surfacesurface

Cilia on Cilia on trachea trachea surfacesurface

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5. Surfaces and Junctions5. Surfaces and Junctionsa. Cell Walla. Cell Wall

Structure:Structure:• Microfibrils of Cellulose in a MatrixMicrofibrils of Cellulose in a Matrix

– Primary Cell WallPrimary Cell WallThin, flexibleThin, flexible

– Secondary Cell WallSecondary Cell WallDeposited in Laminated LayersDeposited in Laminated Layers

• Middle LamellaMiddle Lamella– Sticky polysaccharides (pectins)Sticky polysaccharides (pectins)

Function:Function:• Protects and Maintains ShapeProtects and Maintains Shape• Holds Cells TogetherHolds Cells Together• Prevents Excess Water IntakePrevents Excess Water Intake

49 The Cell WallThe Cell WallThe Cell WallThe Cell Wall

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5. Surfaces and Junctions5. Surfaces and Junctionsb. Communication Structuresb. Communication Structures

DesmosomeDesmosome

desmosomedesmosomeProtein strandsrivet cells together,

but permit passage of substances

Protein strandsrivet cells together,

but permit passage of substances

Protein filamentsin cytoplasmProtein filamentsin cytoplasm

Small intestineSmall intestine Plasma membrane(edge view)Plasma membrane(edge view)

Cells liningsmall intestineCells liningsmall intestine

Tight JunctionTight Junction

Tight junctionsformed by strandsof protein

Tight junctionsformed by strandsof protein

Plasma membrane(edge view)Plasma membrane(edge view)

Cells liningbladderCells liningbladder

Tight junctionsseal membranesto block transport

Tight junctionsseal membranesto block transport

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5. Surfaces and Junctions5. Surfaces and Junctionsc. Attachment Structuresc. Attachment Structures

Gap JunctionsGap Junctions

desmosomedesmosomeGap Junctions:pairs of channelsconnect insides ofadjacent cells

Gap Junctions:pairs of channelsconnect insides ofadjacent cells

LiverLiverPlasma membranePlasma membrane

Liver cellsLiver cells

PlasmodesmataPlasmodesmata

Plasmodesmataallows passageinto adjacent cells

Plasma membrane(lines cell and channels)

Root cells

Cell wall(cellulose)

Middle lamella(pectin)

RootRoot