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B2Topic2 B2.1–PlantandAnimalCells Plantandanimalcellscanbe studiesingreaterdetailusinga lightmicroscope. Lightpassesthroughathinsliceof thespecimen.Lensesmagnifythe specimenmanyBmes. 7Organelles Func.on CellMembrane Controlsmovementintoandoutofthecell. Nucleus ContainsDNA.Controlsthecell Cytoplasm WherechemicalreacBonstakeplace. Mitochondria WhererespiraBonoccurs. CellWall MadeofCELLULOSE.Supportsthecell. Vacuole ContainsCELLSAP.Helpssupporttheplantbykeepingthecellrigid Chloroplast ContainsCHLOROPHYLL.AbsorbsLIGHT.Wherephotosynthesistakesplace B2.2–InsideBacteria Microscopeshaveimprovedinlast350years. Lightmicroscopescanmagnify1500x. Electronmicroscopescanmagnify2000000x. Electronmicroscopesproduceveryclear images. Electronmicroscopesshowmoredetailofthe specimen. 2typesofDNA 4Organelles Func.on ChromosomalDNA AgiantloopofDNAcontainingmostofthegeneBcmaterial. PlasmidDNA SmallloopsofDNAthatcarryextrainformaBon. Flagella Longwhiplikestructuresthataidmovement. CellWall Providessupportbutismoreflexiblethanaplant.Notmade ofcellulose. B2.3-DNA KeyDefiniBon AgeneisasecBonofDNAthatcodes foraspecificprotein. DNAismadeupoftwostrands coiledtoformadoublehelix. Thetwostrandsarelinkedby complementarybasesheldtogether byweakhydrogenbonds. Adenine(A)pairswithThymine(T) Cytosine(C)pairswithGuanine(G) B2.4–ExtracBngDNA 1. Choponionorpeasintochunks. 2. Grindinapestleandmortar. 3. Mixtogetherwithwashingupliquid,saltandwaterand sBr. 4. Incubatethemixtureat60degreesCenBgradefor15 minutesinawaterbath. 5. Filterthemixturethroughfilterpaperintoaboilingtube. 6. Takeicecoldalcoholandpouritslowlydownthesideof theboilingtube.Thealcoholwillformatransparentlayer ontopoftheliquid,asthealcoholislessdense. 7. YouwillseetheDNAbetweenthetwoliquidlayers. B2.5–DNADiscovery London-MauriceWilkins&RosalindFranklinusingX-raysto studyDNAstructure.Fromthepacernsmadetheycouldwork outhowtheatomswerearranged. Cambridge–Watson&CrickwerebuildingamodelofDNAusing datafromotherscienBsts.TheyweregivenacopyofFranklins photographswhichenabledthemtocrackthecode.Franklin didn’tknowtheyhadthephoto. WatsonandCrickpublishedtheirpaperwiththestructureof DNAbutdidn’tacknowledgethephotographtheyused WatsonandCrickwereawardedtheNobelPrizewithMaurice WilkinsbutRosalindFranklinhadalreadydiedsodidnotgetthe prize. B2.5–DNADiscovery TheHumanGenomeProject– InternaBonalProject. 3billionbasesthatmakeupthe humangenomeweresequenced. Ittook13yearsandscienBsts collaboratedusingITtostoreand sharedata. Allhumanshave99.9%oftheir DNAincommon. 5Implica.onsoftheHGP 1. ImprovedgeneBctesBngfor disorders. 2. Newwaysoffindingnew genesthatmayincreaserisk ofcertaindiseases. 3. Newtreatmentsandcures fordiseases. 4. Newwaysoflookingat changesinthegenomeover Bme. 5. Personalisedmedicinesthat workwithaparBcular genotype. B2.6–GeneBcEngineering Knowthisprocess! Defini.on-Theprocessofremovingagenefromoneorganismandinser.ngitinto theDNAofanother. B2.6–GeneBcEngineering Example Advantages Disadvantages Betacarotenein 1. Betacaroteneusedtomakevitamin 1. Couldcrossbreedwithwildriceand goldenriceto A contaminatewildriceDNA reducevitamin 2. VitaminAwillreducedeathand 2. LevelsofbetacaroteneinGolden Adeficiencyin blindness. Ricemightnotbehighenoughto humans makeadifference 3. Canbeexpensivetobuy 4. Producessterileseedssofarmers havetobuythemeveryyear Theproduc.on 1. Canbeusedbyvegans ofhumaninsulin 2. Supplynotaffectedbyanimal byGMbacteria diseases 3. Supplynotaffectedbydemandfor meat 4. CanbemadeinvastquanBBes 5. Cheaper 1. Bacteriaproduceinsulinslightly differentlysomaynotworkfor somepeople Theproduc.on ofherbicide resistantcrops 1. Herbicideresistantweedscan develop 2. CrosspollinaBonwithwildplants 3. PotenBallossofbiodiversity 1. Reducesamountofcropspraying Defini.ons Haploid–Havingonesetofchromosomes. Diploid–Havingtwosetsofchromosomes. Gamete–thesexcells(spermandegg) B2.7–Mitosisand Meiosis Mitosis • TheproducBonoftwo daughtercellswithidenBcal setsofchromosomesinthe nucleusastheparentcell. • ResultsintheformaBonof twogeneBcallyidenBcal diploidcells. • Occursduringgrowthand repairandasexual reproducBon Meiosis • TheproducBonoffour daughtercells,eachwith halfthenumberof chromosomesastheparent cell. • ResultsintheformaBonof geneBcallydifferenthaploid gametes. • Occurswhenmaking gametesonly. AtferBlisaBon,haploidgametesjointoformadiploidzygote. B2.8-Clones Cloning–Anexampleofasexual reproducBon. Howtoproduceaclone 1. Removeadiploidnucleus fromabodycell 2. Enucleateaneggcell 3. Insertdiploidnucleusinto enucleatedeggcell. 4. SBmulatethediploid nucleustodividebymitosis. 5. Implantintosurrogate mother. Enucleate–Removethenucleus B2.8-Clones Advantagesof Cloning Disadvantagesof Cloning RisksofCloning 1. Canmakea geneBcally idenBcalcopyof ananimalwith desirable characterisBcs. 2. Canbeusedto makecopiesof GManimalsto guaranteeall offspringhave thetrait. 1. Clonedanimals olendieyoung. 2. Clonedanimals olenagemore quickly. 3. Complicated process. 1. Veryfew embryosdevelop properlyresulBng indeformiBes. B2.9–StemCells Keydefini.ons StemCell-Anunspecialisedcellthatcandividetoproducemorestemcellsor differenttypesofspecialisedcell. DifferenBate–Becomespecialised. EmbryonicStemCell–CandifferenBateintoalmostanycelltype. AdultStemCell–CandifferenBateintoonlyafewcelltypes. SpecialisedCell–acellwithaparBcularfuncBone.g.neurone,redbloodcell. AdvantagesofStemCell Research DisadvantagesofStemCell Research 1. Embryonicstemcellscan developintoalmostevery typeofhumancell. 2. Bonemarrowstemcells canbeusedtotreat lukaemia. 3. Adultstemcellsmaybe usedinfutureinsteadof embryonicstemcells. 1. 2. 3. RisksofStemCellResearch Embryonicstemcellscan 1. Technologycouldbeused comefromlelover illegally. embryosfromferBlity 2. Riskoftheunknown–long treatments. termeffectsmaynotbe RiskofrejecBonifnot shownforyears. fromapaBentsownstem cells. Couldleadtotumours forming. B2.10–ProteinManufacture B2.10ProteinManufacture Eachaminoacidis codedforby3 specificbases.DNA isatripletcode. Transcrip.on 1. DNAdoublehelixunzips. 2. ThecomplementarymRNAstrandismadeinthenucleusand passesoutthroughapore. Transla.on 1. mRNAacachestotheribosome. 2. AtripletofbasesonthemRNA(codon)codeforaspecificamino acid. 3. tRNAtransfersaminoacidstotheribosome. 4. AminoacidslinktogethertoformpolypepBdes. RNAissinglestrandedbutDNAisdoublestranded. RNAcontainsUracil(U)insteadofthymine(T) B2.11-MutaBons MutaBon–Achangeinthesequenceofbasesinthe geneBccode. 1. Eachproteinhasitsownspecificnumberand sequenceofaminoacids. 2. ThisiscodedforbytheDNA. 3. Therefore,eachproteinisadifferentshapeand hasadifferentfuncBone.g.anenzyme. 4. MutaBonschangethesequenceofthebases, andthereforetheshapeoftheprotein. 5. MostmutaBonsareharmful. 6. RadiaBonandsomechemicalsincigarece smokearemutagensandcausemutaBons. B2.12-Enzymes Enzymesarebiologicalcatalysts.Theyspeedupreac.ons. TheseareexamplesofenzymecatalysedreacBons: 1. DNAReplicaBon–Oneenzymeunzipsthetwo strandsofDNA,theotherjoinsthenewbases togethertomakethenewdoublestrandedmolecule. 2. ProteinSynthesis–RNAPolymerasemakesthemRNA strandfromtheDNAtemplate. 3. DigesBon–Manyenzymesbreaklargermolecules downintosmalleronesindigesBon.Thishappens outsideofthebody.StaindigesBngenzymesin washingpowdersbreakdownstaininclothes. Microorganismsexcreteenzymesontofoodtobreak themdownoutsidethebodyandthenabsorbthe products. B2.13–EnzymesandTemperature EnzymesareSPECIFICtotheirsubstrate.Theyonlycatalyse specificreacBonsinspecificcondiBons.Theyhaveaspecific shapedacBvesite. FactorsthataffectenzymeacBvity: 1. Temperature 2. pH 3. SubstrateConcentraBon. EnzymeacBvitycanbemeasuredbymeasuringthespeedat whichaproductismadee.g.agas,orthespeedatwhicha substrateisusedupe.g.staindigesBon. B2.14–EnzymeAcBon Astemperature increases,sodoes enzymeacBvity,upto 40oC.Aler40oCthe acBvesiteisdenatured andthereacBonstops. AssubstrateconcentraBon increases,sodoesenzyme acBvity,uptoapointwherethe numberofacBvesitesbecomes limiBng.Theonlywaytospeed upthereacBonalerthisisto increasethenumberofacBve sites. Enzymescanneverbekilled.Theycan onlybedenatured,whichiswherethe shapeoftheacBvesitechanges. Enzymeswillonlywork ataspecificpH.Either sideofthisopBmum pH,theenzymewill denatureandnot work. B2.14–EnzymeAcBon Enzymesworklikealockandkey LockandKey EnzymeandSubstrate Onekeywillonlyfitonelock. Onesubstratewillonlyfitoneenzyme. Thekeyfitsthelock. ThesubstratefitstheacBvesite Thekeyunlocksthelock. Thesubstrateischangedintheenzyme Wrongkeywon’tfitthelock. Wrongsubstratewon’tfittheacBvesite. B2.15AerobicRespiraBon. • • • • Allorganismsaremadeofcells EnergyreleasedbyrespiraBon Cellsthatmovemoreneedmoreenergy. Exercise=moreenergyneeded. KeyTerms: RespiraBon-thereleaseofenergyfrom foodmoleculesthatactasfuelforthecell. Diffusion-whensubstancesmovefroman areaofhighconcentraBontoanareaoflow concentraBon. Glucose+Oxygen=CarbonDioxide+Water AerobicrespiraBon=usesoxygentoreleaseenergyfromglucose. Howdoesitgetdelivered? • Glucoseandoxygendiffusefromcapillariestorespiringcells • Carbondioxidediffusesfromrespiringcellstocapillaries • Capillaries-smallestvesselthatcarriesbloodbetweencells/onecellthick • SubstancesmovebydiffusiondownaconcentraBongradient=thediffusion pathway. • Respiringcells=oxygenandglucoselevelsfallastheyareusedupin aerobicrespiraBon/Carbondioxidelevelsincrease. • Gasexchange=thetransferofgases. B2.16invesBgaBngTheeffectsof exercise. • Exercise=increaseheartrateandhastopump bloodfastertothemuscles. • Causesbreathingratetoincreaseandgetdeeper. Why? • Cellsneedmoreoxygenandglucoseastheyneed moreenergy. • Cellsproducemorecarbondioxideasaresult whichneedstoberemoved. B2.17AnaerobicrespiraBon Cardiacoutput=stroke volumexheartrate. Glucoseàlac.cacid • • • • • • • AnaerobicrespiraBon=respiraBonwithoutoxygen Glucoseisbrokendowntosupplyenergytothemuscles ReleaseslessenergythenaerobicandproducesLacBcAcid Amountofbloodpumpedaroundthebodydependsonthestrokevolumeandthe heartrate. Exercise=increaseinheartrateandstrokevolume. LacBcAcidneedstobebrokendown=oxygenusedtobreakitdownintocarbon dioxideandwater. TherequirementofthisoxygentobreakdownthelacBcacidiscalledexcesspostexerciseoxygenconsumpBon(EPOC) B2.18Photosynthesis. Lightandchlorophyll Carbondioxide+wateràglucose+oxygen Photosynthesis=plantsmaketheirownfood Useslightenergytoproduceglucosefromcarbondioxideandwater Glucosestoredasstarch Starch=lotsofglucosemoleculesjoinedtogether. DigesBonbreaksdownstarch=glucose Chlorophyll=greenfoundinchloroplastsabsorbslightfor photosynthesis. • Variegatedleaves=thegreenpartsofaleafcontainthechlorophyll. • • • • • • 2.20Factorsthateffecttherateof photosynthesis. 3factorsthateffectphotosynthesis. • Carbondioxide • Light • Temperature • All3areneededatopBmumamountforphotosynthesistobeatitsbest. • ThelimiBngfactoristheonethatisinshortsupply…..youmayhavelotsofCO2theright temperaturebutliclelightthismeansphotosynthesiswillbeslow. LimiBngfactor= somethingcanaffect therateof photosynthesis. AdaptaBonsofaleaf. Upperepidermis=Bghtlypackedcells=lotsof chloroplasts=lotsofphotosynthesis. Airspaces=providelargesurfaceforcellsto exchangewithgasesintheair. Lowerepidermis=containstomata. Stomata=openandclosetoallowgasesinto theleaf.Locatedundersideoftheleaf. Openinresponsetolight. AllowCarbondioxideinandletsoutoxygen andwatervapour. 3AdaptaBons Hasstomataforgasexchange (carbondioxide,oxygen, watervapour) Containschlorophyllin chloroplaststoabsorblight. Largesurfaceareatoabsorb mostamountoflight. B2.21WaterTransport KeyDefini.ons • Thelossofwaterfromtheleavesdrives transpira.on. • Transpira.on–themovementofwater throughaplantandthelossofwater throughtheleaves. • Osmosis=movementofwaterfromanarea oflowconcentra.ontoanareaofhigh concentra.onthroughapar.allypermeable membrane. • Rootsabsorbnitratesandmineralions dissolvedinwaterbyAc.vetransport. Thisneedsenergyfromrespira.on • Watertransportedbyxylem • Nutrientstransportedbyphloem RootHairCell • Jobofroot=anchorplant andtakeupnutrients. • Roothairfoundonsurface ofroot. • Role–toabsorbwater anddissolvedminerals. • AdaptaBon=largesurface area. B2.22InvesBgaBngOsmosis Osmosis Watercanmoveacrosscellmembranesbecause ofosmosis.Forosmosistohappenyouneed: twosoluBonswithdifferentconcentraBonsand aparBallypermeablemembranetoseparatethem B2.23Organismsandtheir environment KeyTerms • Environment=anorganisms surroundingsincludingthesoil,air, waterandotherorganisminthearea. • Biodiversity=thedifferentplantsand animalsinanarea. • Ecosystem=anareainwhichallthe livingorganismsandallthenonliving organismformarelaBonshipinorder tosurvive. • Habitat=wheretheplantsand animalsarefound/living. • PopulaBon=thenumberofanimalsin agivenarea. • Sampling=lookingatsmallproporBon oftheplantsandanimals. Samplingtechniques= • 1)Pooter=usedtocatchanimals. • 2)Sweepnet=cancatchflying animals. • 3)Pondnet=tocatchaquaBc animals. • 4)pitfalltraps=buriedinthe ground…theorganismsfallin. • 5)quadrats=usedtosamplethe populaBonsizeofplants=random samplingorsystemaBcsampling.= placingthequadratatregular intervalsalongaline. B2 Topic3CommonSystems B2.25FossilsandevoluBon Facts: • Themoonis30‘earths’away • Thesunis11,000‘earths’away Keywords • Fossilrecord–ThecollecBonoffossilsidenBfiedfromdifferentperiodsofBmethatcanbe interpretedtoformahypothesisabouttheevoluBonoflifeonEarth. • Fossil–ThepreservedtracesorremainofanorganismwhichlivedaverylongBmeago • Pentadactyl–fivefingeredorganism Fossils • • FossilsfromdifferentperiodsofBmeshoworganismshavechangedgradually=evolu.on. Fossilrecordhasgaps – Sol.ssuesdecaynotformingfossils – Hardpartsoforganismscouldhavebeendestroyed – Manyfossilsareburiedtoodeeptobefound ScienBstsusingincompletedatasomeBmesmakemistakes Morefossils=moreaccurateconclusions • • EvidenceforEvolu.on • Internalbonesofallvertebrate’slimbsaresimilar • Fossilsoflimblessvertebrateshavethesamefivefingeredstructure • Allvertebtatesevolvedfromonecommonancestor • EvoluBonofthelimbsisduetoadaptaBontohowtheorganismslivedandmoved, B2.26Growth Keywords • Percen.le–ThevalueofavariablebelowwhichacertainpercentageofobservaBonsfall. • StemCell–Anunspecialisedcellthatcandividetoproducemorestemcellsordifferentkindsofspecialisedcells • Differen.ate–Specialise,developintodifferentkindsofcell,asincellsthatbecomenerve,muscleorbonecells • Elonga.on–getnglonger Facts • • • • Growthiswhenanorganisms increasesinsize,lengthand mass Tomonitorgrowthofbabieswe check – Headcircumference – Weight – Height Eachchildiscomparedtoachart todeterminewhichpercen.leof thepopulaBontheyarein. Growthinvolves2things GrowthinPlants • Growallthroughtheirlives • CellsdivideintheMeristem–behindtheBpoftherootandshoot • Cellsalsoelongate • Oldermeristemcellsdifferen.atetobecomespecialisedforexample: – Palisadeleafcell – Roothaircell GrowthinAnimals • Celldivision • Animalsstopgrowingwhentheybecomeadults • Stemcellsareundifferen.ated – Increaseinthenumber • Stemcellscanspecialiseintoallothercells • Adultshaveveryfewstemcells(onlyinbloodand ofcells skeletal.ssues) – Increaseinthesizeof • Mostanimalscannotregrowlimbsorbodyparts. cells Components • Plasma B2.27Blood – Fluidpartofblood – Transportscarbondioxide,hormonesandwaste – Paleyellow • Redbloodcells – Nonucleus=moreroomforhaemoglobin – Madeinthebonemarrow. – Containredpigmenthaemoglobinwhichcarriesoxygen Oxygen+Haemoglobin Oxyhaemoglobin – OxygeniscarriedinthebloodtotheBssuesforaerobicrespira.on – Biconcavedisc=largesurfaceareatovolumeraBoforfasterdiffusionofoxygen • Whitebloodcells – – – – – – • Animportantpartoftheimmunesystem SomeproduceanBbodies(proteinsthatbindtomicrobesanddestroythem) Otherssurroundanddestroyforeigncells Allhaveanucleus Madeinthebonemarrow Allhaveanucleus Platelets – Tinyfragmentsofcells(nonuclei) – Clumptogethertoformclots – Protectthebodybystoppingbleedingandformingascabtostopmicrobesentering. B2.28Theheart • • • • • Thickerwallasit pumpsbloodall aroundthebody • • Septum Deoxygenatedblood(low oxygenlevels) Pumpedtothelungs(by rightventricle)tocollect oxygen Oxygenatedblood returnstoheart(Lel side) Pumpedtothebodycells andBssues(bylel ventricle) Lelandrightsidework togetheratthesame Bme Valvespreventbackflow ofblood Tendonsstopvalves turninginsideout B2.29Thecirculatorysystem 3typesofbloodvessel: Arteries • Carrybloodawayfromtheheart • Havethickmuscularwalls • Havesmallinternallumen • Bloodunderhighpressure Veins • Carrybloodtotheheart • Thinwalls • Largerinternallumen • Bloodunderlowpressure • Valvestopreventbloodflowing backwards Capillaries • Wallisonecellthick • Verylowbloodpressure • Allowsdiffusionbetweenblood andBssues churns B2.30The digesBve system Peristalsis • Musclescontract inwavestomove foodalongthe alimentarycanal (amusculartube runningfrom yourmouthto youranus) B2.31Breaking downfood Keywords Enzyme–aproteinmoleculemadebylivingcellsthatspeedsuptherateofa reacBon Emulsion–amixtureinwhichparBclesofoneliquidaresuspendedinanother liquid. Diges.ngproteins Diges.ng Carbohydrates Enzyme involved Proteases(e.g. pepsin) Carbohydrases(e.g. Lipases amylase) Brokendown into… Aminoacids Simplesugars (glucose) GlycerolandFacyacids Whereitoccurs Stomachfirstthen smallintesBne Mouthandsmall intesBne SmallIntesBne AddiBonal features Amylaseis denaturedby stomachacid • Bilefromthegallbladder breaksdownlargefatglobules intodropletswithalarger surfaceareatohelplipase. • Wesaybileemulsifiesthefat. • Bilealsoneutralisesthe stomachacid. Pepsinhasan opBmumpHof2 (perfectfor stomachacid) Diges.ngFats B2.32Villi Keywords Villi–fingerlikeprojecBonsinthesmallintesBne. Diffusion–movementofparBclesfromanareaofhighconcentraBonto anareaoflowconcentraBondownaconcentraBongradient. InsidetheSmallIntes.ne 1. Digestedfoodpassesintobloodbydiffusion 2. Biggersurfaceareas=morediffusion 3. Finger-likefoldscalledVilliincreasesurfaceareaofsmallintesBne FeaturesofaVillustospeedupdiffusion 1. Goodnetworkofcapillariesmovingabsorbednutrients 2. LowconcentraBonoffood 3. SteepconcentraBongradientmaintained 4. Wallisasinglecelllayer(shorterdistance todiffuse) B2.34ProbioBcsandPrebioBcs–FuncBonalfoods PlantStanolEsters • Oilysubstancesinplants • StopthesmallintesBneabsorbingcholesterol • Lowersbloodcholesterol • Useinmanyfoodslikeyogurtandspreads. Probio.cs • Livebacteria–friendlyorbeneficial • BifidobacteriaorLactobacillus • Theyproducelac.cacidinyourgutandcompaniesclaimtheyimprovehealth • NOTENOUGHEVIDENCEtosupporttheclaimstheyareeffecBve Prebio.cs • Substancesthebodycannotdigest • Theyactasfoodforthebeneficialbacteria • OligosaccharidesareacommonformofprebioBc(containedintomatoes,onionsandasparagus) • Alsofoundinspeciallymadedairyfoodsandsoldascapsules • IncreasingevidencesupportstheirposiBveeffectonhealth