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- Productsmaybeusedwithinthe