1 - Cell Biology –Intro to Cell Biology

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    Introduction to the Study of

    Cells

    Chapter 1

    Pages 1-24

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    Discovery of Cells RobertHooke:corkcomposedofsmallchambersReportedin1665

    Madepossiblebydevelopmentofmicroscope

    Termedporouschambers"cells"Actuallyobservedcellwalls

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    Anton van Leeuwenhoek: first descriptions

    of cellsGroundlensesashobby

    Observedprotistsinpondwatertermed"animacules"

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    Importance of cells realized in 1830s with

    publication of 2 papersMatthiasSchleiden:plantscomposedofcells

    TheodorSchwann:first2tenetsofcelltheory Allorganismsarecomposedofoneormorecells

    Thecellisthestructuralunitoflife

    Schleiden Schwann

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    Rudolf Virchow: third tenet of cell theory in1855

    Cellscanariseonlybydivisionofapreexistingcell

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    Basic Properties of Cells

    1. Highlycomplexandorganized

    Differentlevelsoforganization

    atoms molecules macromolecules complexes organelles cells tissues

    Mostbasicprocessesandstructuresremarkablysimilarinallorganisms

    Informationfromoneorganismgenerallyapplicabletootherorganisms

    Modelorganismsforintensiveinvestigation

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    Bacterium

    Escherichia coli

    Yeast

    Saccharomycescerevisiae

    Model Organisms

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    Nematode

    Caenorhabditis elegans

    Flowering PlantArabidopsis

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    Basic Properties of Cells2. Possessgeneticprogramandmeanstouseit

    Genesblueprintsforcellularconstruction&activities

    3. Capableofreproduction

    4. Acquire

    and

    utilize

    energy

    Requireconstantinputofenergy

    Conversionofelectromagneticradiationtochemical

    energystored

    in

    carbohydrates

    Conversionofstoredchemicalenergyintousableformforcellularactivities(usuallyATP)

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    5. Carryoutavarietyofchemicalreactions

    Sumtotalofchemicalreactionsincellmetabolism

    6. Engageinnumerousmechanicalactivities

    Structuresassembledanddisassembled

    Materialstransportedfromplacetoplace

    Manycellsmove7. Respondtostimuli

    Receiveandreacttosignalsfromothercellsandtheenvironment

    8. Capableofselfregulation

    Obviouswhenregulatorymechanismsbreakdown

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    Two Classes of Cells Basedoninternalcomplexity

    Prokaryoticcellsofarchaebacteriaandeubacteria

    Eukaryoticcellsofallotherorganisms

    Namefrompresence/absenceofnucleus Karyon=kernelornucleus

    Pro

    =

    before Eu=wellortruly

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    Common Characteristics of Prokaryoticand Eukaryotic Cells

    1. Similarconstruction

    of

    plasma

    membrane

    2. GeneticinformationencodedinDNA

    3. Similarmechanisms

    for

    synthesizing

    proteins

    transcriptionandtranslation

    Madebyribosomessimilarbutnotidenticalin

    prokaryoticand

    eukaryotic

    cell

    4. Sharemetabolicpathways

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    Common Characteristics of Prokaryoticand Eukaryotic Cells

    5. Similarmechanism

    for

    ATP

    production

    6. Similarmechanismofphotosynthesis

    (cyanobacteria

    and

    green

    plants)7. Similarmechanismforsynthesizingand

    insertingmembraneproteins

    8. Similarproteasomesstructuresfordigestion

    ofproteinsincytosol

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    Unicellular eukaryotic organisms range fromrelatively simple (yeast)

    to perhaps the most complex ofall cells (protozoa and algae)

    Eukaryotic cells more complex

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    Activities of multicellular organisms dividedamong different types of specialized cells

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    Features of Eukaryotic Cells not Found inProkaryotes

    OrganizationofDNA

    Longlinearstrandsassociatedwithproteins

    Capableofcondensingintomitoticchromosomes

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    DNAsegregatedinnucleus

    Complexmembranedelimitedorganellesin

    cytoplasm

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    Specializedorganellesforaerobicrespirationand

    photosynthesismitochondria

    and

    chloroplasts

    ContainownDNAandproteinsynthesizingmachinery

    Divide

    to

    increase

    number

    Believedtohavecomefromprokaryoticcellsengulfedbyeukaryoticancestor

    mitochondria chloroplast

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    Endoplasmicreticulum(ER)systemofinterconnectedflattened

    sacs

    and

    tubes

    Originof mostcellmembranecomponentsandmaterialsexportedfromcell

    SmoothversusRoughER dependentonpresenceofribosomes

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    Golgiapparatus

    Stackofflattenedsacs ReceivesmoleculesfromERanddirectsthemappropriate

    destination

    Oftenmodifiesmoleculesinprocess

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    Lysosomes(protozoaandanimalcells)

    Oftenirregularlyshapedwithheterogeneousinterior Sitesofintracellulardigestion

    Peroxisomes Membraneboundedwithgranularinteriorandoftenwith

    crystallinecore

    Siteofchemicalreactionscoupledtosynthesisand

    degradationof

    hydrogen

    peroxide

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    Vacuoles(serveaslysosomesinplantcells)

    Differenttypesofsmallvesiclesfortransportbetweenorganelles

    Processesofendocytosisforingestingfluidandparticulatematerial,andexocytosisforreleaseof

    materialfromcell

    2003 Encyclopedia Br itannica, Inc.

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    actin filaments microtubules intermediate filaments

    Complexcytoskeletalsystem

    Givescellmechanicalstrength

    ControlscellshapeOrganizescytoplasmDrivesandguidesmovements

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    Major Differences in Features ofProkaryotic & Eukaryotic Cells

    Eukaryotic Structureofciliaand

    flagellacomplex

    Cellulosiccellwallwhenpresent

    Multiplechromosomes

    Prokaryotic Bacterialflagellaless

    complex

    Peptidoglycancellwallusuallypresent

    Singlecircularchromosome

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    Major Differences in Features ofProkaryotic & Eukaryotic Cells

    Eukaryotic Mitosisutilizing

    microtubulecontaining

    spindle

    Sexualreproductioninvolvingmeiosisand

    fertilization

    Prokaryotic DuplicatedDNAseparated

    bygrowthof cell

    membrane

    CapableofexchangingpiecesofDNAbutnotrue

    sexualreproduction

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    Unique Characteristics of Archaea Cellwallsdonotcontainpeptidoglycan;contain

    auniquemolecularstructureunlikeeubacteria

    oreukaryotes Slayer

    DNAisassociatedwithhistonelikeproteins

    ProteinsynthesizingenzymesandRNApolymerasesmorecloselyresemblethoseof

    eukaryotes

    Membranelipidsareunique,resembling

    neithertheeubacteria oreukaryotes

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    Unique Characteristics of Archaea

    Oftenreferredtoasextremophilesbecauseof

    theenvironmenttheyliveinandthematerials

    theyutilize

    for

    energy

    (sugar,

    ammonia,

    sulfur,

    hydrogen,metals)

    Methanogens oxygenispoisonoustothem

    Halophiles liveinhighsaltenvironments

    Thermoacidophiles orThermophiles Cannot

    surviveat

    low

    temperatures

    (55C)

    Endoliths liveinsiderocks,canutilizemineralsor

    metalsasanenergysource.

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    3 Domain System

    ProposedbyCarlWoesein1990

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    Cells are small

    Diameter of a sphere in microns (m)

    Vo

    lumeofa

    spherein

    nanolite

    rs(nL)

    100 m diameter = 0.52 nL

    300 m diameter = 14.14 nL

    3X versus 27X

    1 m = 10-6 meters1 nm = 10-9 meters

    1 = 10-10 meters

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    Cells are small Synthesisoflimitednumberofmessagesfromset

    amountDNAinagiventime

    Thelargerthevolume,thelongerthetimerequiredtomakenumberofmRNAsneededbycell

    Decreaseinsurfacearea/volumeratiowithincreasein

    size Surfacenotsufficienttotakeupsubstancesrequiredfor

    metabolicactivitiesbeyondcertainsize

    Diffusionresponsibleformovementofmanysubstancesintoandoutofcell Timerequiredfordiffusionpropor