IGCSE-Biology(生物)

IGCSEBiology2012://://://revision-guides.com/gcse/biology.phpCharacteristicsoflivingthings1Listanddescribethecharacteristicsoflivingorganisms.Assimilationisamuchbetterwordthannutrition(becauseplantstakinginandusingCO2andH2Oisnotnutritionbutisassimilation).Thewordassimilationinbiologymeanstakinginsubstancesfromthesurroundingenvironmentandbuildingthemintoyourownstructures.Sensitivityleadstoaresponse.Respirationisoneofthebiochemicalreactionsofcellmetabolism.Sowecanproduceanalternatelist.GrowthAssimilation(replacesnutrition)Metabolism(includesrespiration)ExcretionResponse(sensitivity)ReproductionGAMER2AssimilationTakingininorganicandorganicchemicalsfromthesurroundingenvironment,andusingthemforcellconstructionandcellmetabolism.MetabolismAllthechemicalreactionsthatoccurinacellandresultinwhatwecalllife.ExcretionRemovalofthewasteproductsofmetabolismfromacell.SensitivityUsingthesenseorganstonoticechange.ResponseReactingtoexternalchangefromtheenvironment.ReproductionProducingnewcellsfrompre-existingcells.TobealivingthingsomethingmustexhibitallofGAMER2andbemadeofcells.Cellstructureandorganisation1Statethatlivingorganismsaremadeofcells.Everything,frombacteriatoplantstoinsectstoanimalsareallmadeofone(unicellular)ormorecells(multicellular)CellTheoryLivingorganismsarecomposedofcells.Cellsarethesmallestunitoflife.Cellscomefrompre-existingcells.2Identifyanddescribethestructureofaplantcell(palisadecell)andananimalcell(livercell),asseenunderalightmicroscope.3Relatethestructuresseenunderthelightmicroscopeintheplantcellandintheanimalcelltotheirfunctions.(a)cellsurfacemembrane,whichcontrolswhatentersandleavesthecellThecellmembraneallowsdiffusionofsimplesubstanceswithoutcontrol(passivetransport),e.g.movementofoxygenintothecell,carbondioxideoutofthecellsandionsintooroutofthecells.Additionallythemembraneproteinscancontrolmovementofsubstancesintooroutofthecellandagainstaconcentrationgradient(ifneeded).ThecellusesATPenergytodothis(activetransport)(b)nucleus,whichcontainsDNAwhichisinherited,andwhichcontrolstheactivitiesofthecellNuclearDNAcontainedwithinthecellcarriesthemessagesoflife(genes).Genestellthecellhowtobuildspecificproteinsneededforallthefunctionsofacell.(c)chloroplasts,inwhichphotosynthesistakesplaceChloroplastsaremembraneboundorganellesfoundingreenplants.Eachchloroplastcontainsagreenpigmentproteinmoleculecalledchlorophyll,whichiscapableofusingtheenergyfromsunlighttoproduceglucoseduringphotosynthesis.(d)cellwall,providessupporttothecellsoitcanmaintainitsshape.Italsohelptopreventdamagetothecellmembrane.Thecellwallhaslargespacesinitallowinganythingtopasseasily,itisfullypermeable.4Describethedifferencesinstructurebetweentypicalanimalandplantcells.AnimalCellsPlantcellsNocellwallCellwallNovacuoleMayhaveavacuole,butnotalwaysNochloroplastsChloroplastsinphotosynthesizingcellsHeterotrophic–musttakeinorganicmoleculesfromthesurroundingenvironmentAutotrophic–canmaketheirownOrganicmoleculesfrominorganicMoleculesusingphotosynthesis.Usetheorganicmolecules-Glucose-Lipids-Aminoacids-NucleicacidsUsetheinorganicmolecules-Water-Carbondioxide-Nitrates-PhosphatesRelyonplantsforfoodSelfsufficient5Calculatemagnificationandsizeofbiologicalspecimensusingmillimetresasunits.Magnification=Drawingorimagesizeforthespecimenbiological(mm)Actualsizeofthebiologicalspecimen(mm)Howbigisacell?://://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.htmlO2,CO2,andsmallionscandiffuseinoroutofcells.2Describetheimportanceofdiffusionofgasesandsolutesandofwaterasasolvent.ingorganismsWater(H2O)isnotanorganiccompoundbutitisessentialforlifeonEarth.Cellmembranesareshapedintohollowspheresbecauseofthepolarnatureofwaterandthewayitinteractswithlipidmoleculesthatmakeupthebilipidlayer.Waterhasahighthermalcapacity.Thismeansittakesalotofenergytochangethetemperatureofwater.Thiskeepstemperaturestableinlivingcells.Waterdissolvesmanychemicalsallowingchemicalreactionstooccurmoreeasily.Waterallowsgasessuchasoxygenandcarbondioxidetodiffuseanddissolveintothewatermakingthetransportofthesegasesmuchfasteracrosscellmembranes.Waterflowsandisthereforeagreattransporterofsubstances.Enzymes1Defineenzymesasproteinsthatfunctionasbiologicalcatalysts.Catalystsspeedupchemicalreactions,withoutthemselvesbeingpartofthereactantsortheproducts.Enzymesarespeciallyfoldedproteins.Thefoldingdependsontheexactorderoftheaminoacidsthatmakeuptheprotein.Thefoldedproteinthenhasonesideofits3Dshapecalledanactivesite.Theactivesiteisaspecificmatchforspecificsubstrate/s(reactant/s)inachemicalreaction.Ifanenzymeisaffectedbyhightemperatureorby