Cells and theirCells and theirOrganellesOrganelles

Cell TheoryCell Theory

Scientific theories have two components:Scientific theories have two components: Pattern and processPattern and process

All organisms are made of cells (pattern).All organisms are made of cells (pattern). All cells arise from pre-existing cellsAll cells arise from pre-existing cells

(process).(process).

Relative SizesRelative Sizes

Cellular SizesCellular Sizes

ProkaryotesProkaryotes

BacteriaBacteria Lack a distinct nucleusLack a distinct nucleus No cytoskeleton and essentially no organellesNo cytoskeleton and essentially no organelles Often have a cell wallOften have a cell wall

Two Domains or Groups of Prokaryotes:Two Domains or Groups of Prokaryotes: Eubacteria - found commonlyEubacteria - found commonly Archaea - found in harsh environments;Archaea - found in harsh environments;

discovered by Dr. Carl Woesediscovered by Dr. Carl Woese

EukaryotesEukaryotes

Protozoa, Fungi, Plants and AnimalsProtozoa, Fungi, Plants and Animals Have a distinct nucleusHave a distinct nucleus Great subcellular complexity representedGreat subcellular complexity represented

by cytoplasm and the variety of organellesby cytoplasm and the variety of organelles Significantly larger than prokaryotesSignificantly larger than prokaryotes Can be single-celled organisms or complexCan be single-celled organisms or complex

multicellular organismsmulticellular organisms

The NucleusThe Nucleus

Most visible of all organellesMost visible of all organelles Usually centrally locatedUsually centrally located Houses DNAHouses DNA Contains the nucleolusContains the nucleolus

Site of ribosomal RNA processing andSite of ribosomal RNA processing andribosomal subunit organizationribosomal subunit organization

Has a unique membrane called the nuclearHas a unique membrane called the nuclearenvelope - envelope - know the features of thisknow the features of this!!

Endoplasmic ReticulumEndoplasmic Reticulum

Begins as an extension of the nuclearBegins as an extension of the nuclearmembranemembrane

Site of synthesis for cell membraneSite of synthesis for cell membranecomponents and export moleculescomponents and export molecules

Two varieties:Two varieties: Smooth : lipids, cell membrane componentsSmooth : lipids, cell membrane components Rough : exported proteinsRough : exported proteins

Evolution of MembranesEvolution of Membranes

There is speculation that the nuclear and ER membranesThere is speculation that the nuclear and ER membranesresulted from an invagination of the plasma membrane.resulted from an invagination of the plasma membrane.

Golgi ApparatusGolgi Apparatus

Consists of a stack of membrane boundConsists of a stack of membrane boundsacssacs

Receives, modifies, sorts and packagesReceives, modifies, sorts and packagesmolecules from the ERmolecules from the ER

Small portions of the Golgi pinch off toSmall portions of the Golgi pinch off tocreate vesicles for transport and deliverycreate vesicles for transport and delivery

VesiclesVesicles

LysosomesLysosomes Site of intracellular digestionSite of intracellular digestion Rarely found in plant cellsRarely found in plant cells

PeroxisomesPeroxisomes Site where hydrogen peroxide is generatedSite where hydrogen peroxide is generated

and degradedand degraded Secretory vesiclesSecretory vesicles

Move secretions such as hormones from theMove secretions such as hormones from theGolgi to the plasma membraneGolgi to the plasma membrane

Vesicle TransportVesicle Transport

Endocytosis - importEndocytosis - import A portion of the cellA portion of the cell

membrane invaginatesmembrane invaginatesand pinches off toand pinches off todeliver extracellulardeliver extracellularcontents to the insidecontents to the inside

Exocytosis - exportExocytosis - export A vesicle fuses withA vesicle fuses with

the cell membrane andthe cell membrane andexpels its contents intoexpels its contents intothe extracellular spacethe extracellular space

MitochondriaMitochondria The The ““power plantspower plants”” of the cell of the cell

Produce almost all of the energy necessary for cellularProduce almost all of the energy necessary for cellularprocesses in the form of ATPprocesses in the form of ATP

Cellular respiration - uses OCellular respiration - uses O22 and produces CO and produces CO22

About the size of bacteriaAbout the size of bacteria Why might this be?Why might this be?

Two membranesTwo membranes Outer is smoothOuter is smooth Inner is highly convoluted - Inner is highly convoluted - Why?Why?

Contain their own DNA, divide in twoContain their own DNA, divide in two

ChloroplastsChloroplasts

Large green organelles in higher plantsLarge green organelles in higher plantsand algae; absent in animals and fungiand algae; absent in animals and fungi

More complex than mitochondriaMore complex than mitochondria Two surrounding membranesTwo surrounding membranes An internal stack of membranes containingAn internal stack of membranes containing

chlorophyllchlorophyll Capture sunlight energy viaCapture sunlight energy via

photosynthesisphotosynthesis Contain their own DNA, divide in twoContain their own DNA, divide in two

Mitochondrial OriginMitochondrial Origin

It is thought that mitochondria arose as a resultIt is thought that mitochondria arose as a resultof a eukaryote engulfing a prokaryote.of a eukaryote engulfing a prokaryote.

CytosolCytosol

Internal pool of the cell excludingInternal pool of the cell excludingmembrane-bound organellesmembrane-bound organelles

Contained by plasma membraneContained by plasma membrane Loaded with proteins responsible for:Loaded with proteins responsible for:

MetabolismMetabolism DivisionDivision TranslationTranslation SignalingSignaling

CytoskeletonCytoskeleton

System of filaments transversing theSystem of filaments transversing thecytoplasmcytoplasm

Anchored to the cell membrane or a pointAnchored to the cell membrane or a pointadjacent to the nucleusadjacent to the nucleus

Provides direction for organelles movingProvides direction for organelles movingwithin the cellwithin the cell

Provides shape and mechanical strengthProvides shape and mechanical strength Responsible for cell mobilityResponsible for cell mobility

MicrotubulesMicrotubules

Largest cytoskeletalLargest cytoskeletalcomponentcomponent

Primarily responsiblePrimarily responsiblefor separatingfor separatingduplicatedduplicatedchromosomes duringchromosomes duringcell divisioncell division

Very small, hollowVery small, hollowtubestubes

Intermediate FilamentsIntermediate Filaments

IntermediateIntermediatecytoskeletalcytoskeletalcomponentcomponent

Provide mechanicalProvide mechanicalstrengthstrength

Actin FilamentsActin Filaments

Smallest cytoskeletalSmallest cytoskeletalcomponentcomponent

Also calledAlso calledmicrofilamentsmicrofilaments

Primarily responsiblePrimarily responsiblefor contractionfor contraction

Predominant inPredominant inmuscle cellsmuscle cells

CentrosomeCentrosome

Centrally locatedCentrally located Site of microtubule production andSite of microtubule production and

organizationorganization Short cylinders that contain an array ofShort cylinders that contain an array of

microtubules in nine groupsmicrotubules in nine groups Replicate themselves during division andReplicate themselves during division and

move to opposite poles of the nucleus,move to opposite poles of the nucleus,then of the cellthen of the cell

Lacking in plant cellsLacking in plant cells

Cell MembraneCell Membrane

Amphipathic lipid bilayer enclosing theAmphipathic lipid bilayer enclosing thecellcell Hydrophilic heads at membrane surfacesHydrophilic heads at membrane surfaces Hydrophobic tails intermingle in interiorHydrophobic tails intermingle in interior

Creates and maintains uniqueCreates and maintains uniqueenvironment withinenvironment within

Controls entrance and exit of materialsControls entrance and exit of materials Strongly associated with proteinsStrongly associated with proteins

VacuoleVacuole

Generally small in animal cellsGenerally small in animal cells Responsible for intracellular digestion andResponsible for intracellular digestion and

removal of cellular wasteremoval of cellular waste

Much larger in plant cellsMuch larger in plant cells Responsible for maintaining turgor pressureResponsible for maintaining turgor pressure

Rigidity and upright supportRigidity and upright support

Cell WallCell Wall

Found in plants and prokaryotesFound in plants and prokaryotes Rigid structure surrounding cellRigid structure surrounding cell

membranemembrane Comprised of the polysaccharide celluloseComprised of the polysaccharide cellulose Provides structural support and shapeProvides structural support and shape Acts as a barrierActs as a barrier

Cellular OrganellesCellular Organelles

MicroscopyMicroscopy

In order to visualize cells and theirIn order to visualize cells and theircomponents we must employ microscopycomponents we must employ microscopy

Types:Types: LightLight FluorescentFluorescent ConfocalConfocal TEMTEM SEMSEM

Light MicroscopyLight Microscopy

Allows magnification of up to oneAllows magnification of up to onethousand timesthousand times

Resolution to 0.2 Resolution to 0.2 µµM: cells and nucleusM: cells and nucleus Requires:Requires:

Bright light focused on specimenBright light focused on specimen Specimen prepared to allow passage of lightSpecimen prepared to allow passage of light Set of lenses must focus an imageSet of lenses must focus an image

Types: brightfield, phase-contrast,Types: brightfield, phase-contrast,interference-contrastinterference-contrast

Fluorescent MicroscopyFluorescent Microscopy

Similar to light microscopeSimilar to light microscope Requires fluorescent dye for cell stainingRequires fluorescent dye for cell staining Specimen illumination differs by twoSpecimen illumination differs by two

filters:filters: Filter 1 (before specimen) only allows passageFilter 1 (before specimen) only allows passage

of wavelengths that excite the particular dyeof wavelengths that excite the particular dye Filter 2 (after specimen) only allows passageFilter 2 (after specimen) only allows passage

of wavelengths emitted when dye fluorescesof wavelengths emitted when dye fluoresces Used to selectively visualize molecules inUsed to selectively visualize molecules in

the cellthe cell

Confocal MicroscopyConfocal Microscopy

Fluorescent scope with specimenFluorescent scope with specimenillumination coming from a laserillumination coming from a laser

Provides optical sectioning as itProvides optical sectioning as itspecifically focuses on one plane, or onespecifically focuses on one plane, or oneparticular depth in the specimen, at a timeparticular depth in the specimen, at a time

Transmission ElectronTransmission ElectronMicroscopyMicroscopy

Allows magnification of up to one millionAllows magnification of up to one milliontimestimes

Resolution of 2 nm: organelle detailsResolution of 2 nm: organelle details Uses a beam of electrons instead of a beamUses a beam of electrons instead of a beam

of light for illuminationof light for illumination Specimen must be extremely thin and in aSpecimen must be extremely thin and in a

vacuumvacuum Contrast supplied by heavy metal dyesContrast supplied by heavy metal dyes

Scanning Electron MicroscopyScanning Electron Microscopy

Resolution from 3 nm to 20 nmResolution from 3 nm to 20 nm Specimen is coated with a very thin film ofSpecimen is coated with a very thin film of

heavy metalheavy metal Uses a beam of electrons instead of lightUses a beam of electrons instead of light Generates a detailed 3-D surface image ofGenerates a detailed 3-D surface image of

organelle structureorganelle structure

Organelles and DiseaseOrganelles and Disease

Organelles provide efficiency and anOrganelles provide efficiency and anexcellent division of labor for the cellexcellent division of labor for the cell

However, as with any system, the greaterHowever, as with any system, the greaternumber of parts involved, the greater thenumber of parts involved, the greater thechances of something going wrongchances of something going wrong Each organelle can have myriad defects thatEach organelle can have myriad defects that

lead to a host of disorders and diseaseslead to a host of disorders and diseases

Lysosome MalfunctionsLysosome Malfunctions

As you can imagine, lysosomeAs you can imagine, lysosomemalfunction can have dire consequencesmalfunction can have dire consequences Asbestosis - asbestos fibers lodge inAsbestosis - asbestos fibers lodge in

lysosomes and cause them to leaklysosomes and cause them to leak Results in severe coughing and shortness of breathResults in severe coughing and shortness of breath

Rheumatoid arthritis - lysosomal enzymesRheumatoid arthritis - lysosomal enzymesleak into joint fluidleak into joint fluid Results in painful joints due to inflammationResults in painful joints due to inflammation

Lysosomal Storage DiseasesLysosomal Storage Diseases

Inclusion-cell diseaseInclusion-cell disease Lysosomal enzymes are missingLysosomal enzymes are missing

Results in skeletal and facial deformities andResults in skeletal and facial deformities andmental retardationmental retardation

Tay-Sachs diseaseTay-Sachs disease Absence of a single lysosomal enzymeAbsence of a single lysosomal enzyme

Results glycolipid accumulation in the brain,Results glycolipid accumulation in the brain,leading to rapid mental deterioration, paralysisleading to rapid mental deterioration, paralysisand deathand death

Diseases associated withDiseases associated withMitochondrial DisordersMitochondrial Disorders

ParkinsonParkinson’’s diseases disease AlzheimerAlzheimer’’s diseases disease HuntingtonHuntington’’s diseases disease Multiple sclerosisMultiple sclerosis StrokeStroke Amyotrophic lateral sclerosis (ALS)Amyotrophic lateral sclerosis (ALS)

All appear to be associated with damage toAll appear to be associated with damage tothe electron transport chainthe electron transport chain

Other AssociationsOther Associations

AlzheimerAlzheimer’’s disease and ALS are alsos disease and ALS are alsothought to be associated with defects ofthought to be associated with defects ofthe Golgi.the Golgi.

Stroke is associated with ER defects.Stroke is associated with ER defects. Hemolytic anemias are associated withHemolytic anemias are associated with

defects of the red blood cell membrane.defects of the red blood cell membrane.

SynthesisSynthesis

The cell is a magnificent entity.The cell is a magnificent entity. It is minute.It is minute. It is complex.It is complex. It is efficient.It is efficient.

We have a variety of microscopic tools toWe have a variety of microscopic tools toreveal various degrees of detail.reveal various degrees of detail.

Dire consequences can result when anyDire consequences can result when anypart are the machinery malfunctions.part are the machinery malfunctions.