O level Bio notes

Cells 1. Organellesofacell Part Details Cellmembrane D:partiallypermeableF:controlsmovementoffoodsubstancesandoxygeninto,andwasteproductsoutofthecelltomaintainchemicalbalancewithcell’ssurroundingmedium Cytoplasm D:jelly-likesubstanceF:servesassitefornumerousmetabolicchemicalreactionsandcellactivities Nucleus D:consistsofnucleoplasm,chromatinandanucleolus;surroundedbynuclearenvelopeF:nucleolus:playsaroleinthemakingofproteins;nuclearenvelope:separatescontentsofthenucleusfromrestofcytoplasm;chromatin:eachchromatinthreadismadeofproteinsanddeoxyribonucleicacid(DNA),whichstoreshereditaryinformationandinstructionscellneedsforcarryingoutactivities Cellwall D:madeofcellulose;fullypermeableF:protectscellfrominjury;givesplantcellafixedshape Roughendoplasmicreticulum(RER) D:ribosomesattachedtooutersurface;continuouswithnuclearenvelopeF:containsribosomesthatsynthesiseproteins;transportsproteinsmadebyribosomestotheGolgibodyforsecretionoutofthecell Smoothendoplasmicreticulum(SER) D:doesnothaveribosomesattachedtooutersurface;moretubularthanRERF:synthesisesfatsandsteroids;carriesoutdetoxification Ribosomes D:smallroundstructures;eitherattachedtothemembraneoftheRERorliefreelyinthecytoplasmF:ribosomesattachedtoRERmakeproteinsthatareusuallytransportedoutofcell;ribosomeslyingfreelyincytoplasmmakeproteinsthatareusedwithincytoplasmofcell Golgibody D:consistofastackofflattenedspacessurroundedbymembranes;vesiclescanbeseenfusingwithoneoftheGolgibodyandpinchingofffromoppositesideF:chemicallymodifiessubstancesmadebyER;storesandpackagesthesesubstancesinvesiclesforsecretionoutofcell Mitochondria D:small,oval-shaped;hasitsowngeneticmaterialF:carriesoutaerobicrespirationtoreleaseenergy Chloroplasts D:containgreenpigmentchlorophyll;hasitsowngeneticmaterialF:chlorophylltrapslightenergy;chloroplastscarryoutphotosynthesis

Vacuoles D:inplantcells:onelargeandcentral,surroundedbytonoplast;inanimalcells:small,numerousandtemporaryF:inplantcells:containscellsapwhichcontainsdissolvedsubstancessuchassugars,dissolvedmineralsaltsandaminoacids;inanimalcells:containswaterandfoodsubstances 2. Histologyofcells Nucleus - Nucleushavelargersizesthanotherorganelles RER - Directlyoutsidethenucleus- Inalayeredfashion,isextensive-verylongstacked‘pratas’(toomanylayersforaGolgiapparatus-howtodifferentiate)

SER - notacontinuouslayer,getcutoff- canbecontinuouswithroughER Golgibody - Curved- mustlabelthevesiclesarounditassecretoryvesicles- ‘stacked-offprata’,“wi-fi”sign Mitochondrion

Chloroplast 3. Proteinsynthesispathwaya. mRNA(instructions)synthesisedbynucleusb. leavesnucleusthroughnuclearporesc. MovestoRERwhenribosomesusethemastemplatesd. forsynthesisofpolypeptidese. PolypeptidesmovewithinRERandaremodifiedandassembledintoproteinsf. Proteins are transferred to Golgi apparatus for modification and packaging fortransportinto(secretory)vesicleswhichpinchoff.g. Secretoryvesiclesfusewithcellmembrane,releasingproteinsoutsidethecell. *note(s):- Proteinsynthesis:mayneedtomentiontRNA- Productsmaybeusedwithinthecell(intracellular)- Productsreleasedoutsidethecell:usesecretoryvesicles 4. Comparisonbetweenplantandanimalcells Plantcell Animalcell Cellwallpresent Cellwallabsent Chloroplastspresent Chloroplastsabsent Centriolesabsent Centriolespresent Alargecentralvacuole Vacuolesaresmall,numerousandtemporary 5. DifferentiationDifferentiationistheprocessbywhichacellbecomesspecialisedforaspecificfunction.a. RBCi. Biconcave(andelastic)ii. ContainsHbiii. Nonucleusiv. Elasticb. RHCi. Concentratedcellsapii. Longnarrowprotrusionc. Xylemi. Nocrosswalls/continuouslumen

ii. Nocytoplasm/deadiii. Lignifiedd. Epithelialcelle. Cilliatedcellsoftrachea MovementofSubstances 1. Diffusiona. Diffusionisthenetmovementofparticlesfromaregionofhigherconcentrationtoaregionoflowerconcentration,downaconcentrationgradient.b. Condition(s):Theremustbeaconcentrationgradient.c. Canassumethatmovementofonetypeofparticleisunaffectedbythepresenceofothertypesofparticles.2. OsmosisOsmosisisthenetmovementofwatermoleculesfromasolutionofhigherwaterpotentialtoasolutionoflowerwaterpotential,throughapartiallypermeablemembrane,downawaterpotentialgradient.Condition(s):p.p.m;waterpotentialgradient.a. Templatei. Comparewp.Thereisahigherwpinthe__thaninthe__.ii. DescribemovementThereisanetmovementofwatermoleculesfrom__to__byosmosis.iii. ResultSo____b. Knowhowosmosiscausesbendingi. Ifonegroupofcellsisunabletoshrinkorexpandduetoawaxycuticleorishardened, then there will be uneven expansion/contraction resulting inbendingii. Examples:guardcellshavewallthickerononeside;cuttingofstrips)c. Sourcesoferrorforosmosisexperimentsi. Epithelial layers can interfere (do NOT use vague language! If there is aneffect, state the effect and why it occurs) withresults-e.g.affectsmassmeasuredii. Evaporation(DODGY) - e.g. usingtest tubevs petri dish-largerexposedsurfaceareausingpetridish,solutionwillevaporatefasteriii. Dilutioneffects(DODGY)watermovingoutofthepotatostripswillaffecttheconcentrationof thesolution- better wayistouselargervolumesusinglargercontainersiv. Differentpartsoftheorganmayhavedifferentcompositionsinthetissue,leadingtodifferentresults3. Activetransporta. Activetransportistheprocessinwhichenergyisusedtomovetheparticlesofasubstanceacrossamembrane(notp.p.m/cellmembrane)againstitsconcentrationgradient.a. Requiresenergy(fromrespiration,whichrequiresoxygen)-showthisunderstandinginexplanations

b. Lowerconcentrationtohigherconcentration-however,activetransporthappenswhenthebodyneedstoabsorbimportantsubstances,evenwhenitisdownaconcentrationgradient,sothatthesesubstancescanbeabsorbedmorequickly(e.g.selectivereabsorptionofglucosefromglomerularfiltrate;absorbingionstocreateaconcentratedcellsap;absorptionofglucose,aminoacidsandfattyacidsandglycerolfromsmallintestine;absorptionofpotassiumionsbyguardcells,etc)c. Activetransportdoesnotrequireap.p.m,bydefinition(butinthesyllabus,you’llusuallyseeactivetransporthappeningacrossalivingp.p.msinceactivetransportrequiresenergy) 4. Comparison Diffusion Osmosis Doesnotrequirep.p.m Requiresp.p.m Movementofanytypeofparticles Movementofwatermolecules Higherconcentrationtolowerconcentration Higherwaterpotentialtolowerwaterpotential Similarities(diffusion&osmosis):a. Bothpassiveprocesses-noenergyrequiredb. Bothcanoccuracrossap.p.mc. Both involve the movement of substance from higher concentration of thatsubstancetoalowerconcentrationofthatsubstanceuntil dynamicequilibriumisreached(DODGY) a. Diffusioni. Absorptionofnutrientsinsmallintestineii. Absorptionofoxygeninalveolib. Osmosisi. Absorptionofwaterinrootsii. Absorptionofwaterinsmallintestine/largeintestinec. Activetransporti. Absorptionofnutrientsinsmallintestineii. MovementofK+ionsintoguardcells

Nutrients 1. Watera. Transportmediumb. Mediumforchemicalreactionsc. Keycomponentofmanysecretions&bodilyfluidsd. Lubricatessurfacese. Usedinhydrolyticreactionsf. Controllingbodytemperature:i. Waterinsweatevaporatesfromskinsurface → latentheatlost → coolbodydownii. Maintainstemperatureofthebodysinceithashighheatcapacity2. Fibrea. Providesroughage;addsbulktofoodsothatthealimentarycanalcanpropelfoodalongmoreeasilythroughperistalsis,reducingtheriskofconstipationandallowingfoodtopassthroughthedigestivesystemfaster3. Carbohydratesa. MadeupofC,HandOb. Madeupofmonosaccharideunits(glu,gal,fru)joinedbyglycosidicbondstoformdisaccharides(maltose-glu-glu,lactose-glu-gal,sucrose-glu-fru)andpolysaccharides(starch,glycogen,cellulose)throughcondensationreactionsc. Monosaccharidesi. Glucose:foundinplantsandanimalsii. Fructose:commoninplants,rareinanimalsiii. Galactose:presentinmilksugarofmammalsd. Disaccharidesi. Sucrose:foundinplants,notinanimals,sucrose=glucose+fructoseii. Maltose:occursingerminatinggrains,maltose=glucose+glucoseiii. Lactose:occursinmilkofmammals,lactose=glucose+galactosee. Polysaccharidesi. Starch:storageformofcarbohydratesinplants;canbedigestedtoglucoseforaerobicrespirationtoreleaseenergyii. Cellulose:foundincellwalls,whichprotectplantcellsfrominjury;cannotbedigestedinintestinesofhumans;enzymethatbreaks