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AQA GCSE Biology (Combined Science) Unit 2: Organisation
Principles of Organisation
Food Tests (Required Practical) Effect of pH on the Rate of
Reaction of Amylase (Required Practical)The Digestive System
6.
Add2cm3ofstarchsolutionintothetesttube,usingadifferentmeasuringcylindertomeasure,andbeginatimer(leavethetimertoruncontinuously).
7.
After10seconds,useapipettetoextractsomeoftheamylase/starchsolution,andplaceonedropintothefirstwellofthespottingtile.Squirttheremainingsolutionbackintothetesttube.
8.
Continuetoplaceonedropintothenextwellofthespottingtile,every10seconds,untiltheiodineremainsorange.
9.
Recordthetimetakenforthestarchtobecompletelydigestedbytheamylasebycountingthewellsthatweretestedpositiveforstarch(indicatedbytheblue/blackcolourchangeoftheiodine).Eachwellrepresents10secondsoftime.
10. Repeatsteps1to8forpHvalues7and10.
cell tissue organ organ system organism
Cells are the basicbuilding blocks of alllivingthings.
Agroupofcellswithasimilarstructureandfunctioniscalledatissue.
Anorganisacombinationoftissuescarryingoutaspecificfunction.
Organsworktogetherwithinanorgansystem.
Organsystemsworktogethertoformwholelivingorganisms.
What are you testing for?
Which indicator do you use?
What does a positive result look like?
sugar Benedict’sreagent
Onceheated,thesolutionwillchangefromblue-greentoyellow-red.
starch iodine Blue-blackcolourindicatesstarchispresent.
protein biuret Thesolutionwillchangefrombluetopink-purple.
lipid sudanIII
Thelipidswillseparateandthetoplayerwillturnbrightred.
Iodineisusedtotestforthepresenceofstarch.
Ifstarchispresent,thecolourwillchangetoblue-black.
Theindependent
variableintheinvestigationisthepHofthebuffersolution.
Thedependent
variableintheinvestigationisthetimetakenforthereactiontocomplete(howlongittakesforallthestarchtobedigestedbytheamylase).
Method:1.
UsethemarkerpentolabelatesttubewiththefirstvalueofpHbuffer
solution(pH4)andstanditinthetesttuberack.
2. Intoeachwellofthespottingtiles,placeadropofiodine.
3.
Usingameasuringcylinder,measure2cm3ofamylaseandpourintothetesttube.
4.
Usingasyringe,measure1cm3ofthebuffersolutionandpourintothetesttube.
5.
Leavethistostandforfiveminutesandthenusethethermometertomeasurethetemperature.Makeanoteofthetemperature.
Thepurposeofthedigestivesystemistobreakdownlargemoleculesintosmaller,solublemolecules,whicharethenabsorbedintothebloodstream.Therateofthesereactionsisincreasedbyenzymes.
tonguemouth
livergallbladder
smallintestine
anus
salivaryglands
oesophagus
stomach
pancreas
largeintestine
rectum
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AQA GCSE Biology (Combined Science) Unit 2: Organisation
The Heart and Blood Vessels
Theheartisalargemuscularorganwhichpumps blood
carryingoxygenorwasteproductsaroundthebody.Thelungsarethesiteofgas
exchange
whereoxygenfromtheairisexchangedforwastecarbondioxideintheblood.Oxygenisusedintherespirationreactiontoreleaseenergyforthecellsandcarbondioxideismadeasawasteproductduringthereaction.
glucose + oxygen carbon dioxide + water + [energy]
Thethreetypesofbloodvessels,shownabove,areeachadaptedtocarryouttheirspecificfunction.
Capillariesarenarrowvesselswhichformnetworkstocloselysupplycellsandorgansbetweentheveinsandarteries.Thewallsofthecapillariesareonlyone
cell thick,whichprovidesashortdiffusion
pathwaytoincreasetherateatwhichsubstancesaretransferred.
Thetablebelowcomparesthestructureandfunctionofarteriesandveins:
The Heart as a Double Pump
The Heart as Pacemaker
vein artery capillary
Enzymes
Anenzymeisabiologicalcatalyst;enzymesspeedupchemicalreactionswithoutbeingchangedorusedup.
Thishappensbecausetheenzymelowerstheactivation
energyrequiredforthereactiontooccur.Enzymesaremadeupofchainsofaminoacidsfoldedintoaglobularshape.
Enzymeshaveanactive
sitewhichthesubstrate(reactants)fitsinto.Enzymesareveryspecificandwillonlycatalyseonespecificreaction.Ifthereactantsarenotthecomplimentaryshape,theenzymewillnotworkforthatreaction.EnzymesalsoworkoptimallyatspecificconditionsofpHandtemperature.InextremesofpHortemperature,theenzymewilldenature.Thismeansthatthebondsholdingtogetherthe3Dshapeoftheactivesitewillbreakandtheactiveshapewilldeform.Thesubstratewillnotbeabletofitintotheactivesiteanymoreandtheenzymecannotfunction.
Theheartworksasadouble
pumpfortwocirculatorysystems;thepulmonarycirculationandthesystemic
circulation.The pulmonary circulation serves thelungs and bring
deoxygenated blood toexchange waste carbon dioxide gas
foroxygenatthealveoli.Thesystemiccirculationservestherestofthebodyandtransportsoxygenandnutrientsfromdigestionto
the cells of the body, whilst carrying
carbondioxideandotherwasteawayfromthecells.The systemic circulation
flows through the
wholebody.Thismeansthebloodisflowingatamuchhigherpressurethaninthepulmonarycircuit.
Theproductsofdigestionareusedtobuildnewcarbohydratesandproteinsandsomeoftheglucoseisusedforrespiration.
Bileisproducedintheliverandstoredinthegallbladder.
Itisanalkalinesubstancewhichneutralisesthehydrochloricacidinthestomach.Italsoworkstoemulsify
fatsintosmalldroplets.Thefatdropletshaveahighersurface
areaandsotherateoftheirdigestionbylipaseisincreased.
Enzyme Reactant Product
amylase starch sugars(glucose)
protease protein aminoacids
lipase lipid glycerolandfattyacids
Artery Vein
directionofbloodflow awayfromtheheart towardstheheart
oxygenatedordeoxygenatedblood?
oxygenated(exceptthepulmonaryartery)
deoxygenated(exceptthepulmonaryvein)
pressure high low(negative)
wallstructure
thick,elastic,muscular,connectivetissueforstrength
thin,lessmuscular,lessconnectivetissue
lumen(channelinsidethevessel)
narrow wide(withvalves)
The rate of the heart beating is very carefully, and
automatically, controlled within the heartitself.Located in the
muscular walls ofthe heart are small groups ofcells which act as
pacemakers. They produce electrical impulseswhichstimulate
thesurroundingmuscletocontract,squeezingthechambersoftheheartandpumpingtheblood.
The sino-atrial node (SAN) is located near
therightatriumanditstimulatestheatriatocontract.Theatrio-ventricular
node (AVN) is located inbetween
theventriclesandstimulatesthemtocontract.
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AQA GCSE Biology (Combined Science) Unit 2: Organisation
Drugs–illegaldrugs(e.g.ecstasyandcannabis)canleadtoincreasedheartrateandbloodpressure,increasingtheriskofheartdisease.
Alcohol – regularly exceeding unit guidelines for alcohol can
lead to increasedbloodpressureandriskofheartdisease.
Artificialpacemakerscanbesurgicallyimplantedintoapersoniftheirheartnodesarenotfunctioningcorrectly.
Coronary Heart Disease
Coronary heart disease isaconditionresulting fromblockages in
thecoronary
arteries.Thesearethemainarterieswhichsupplybloodtotheheartitselfandtheycanbecomeblockedbybuild-upoffatty
deposits.
IntheUKandaroundtheworld,coronaryheartdiseaseisamajorcause
ofmanydeaths.
Themainsymptomscanincludechest pain,heart attackorheart failure.
Yet,notallpeoplesufferthesamesymptoms,ifanyatall.Lifestyle
factorscan increase
theriskofapersondevelopingcoronaryheartdisease.
Diet–ahigh-fatdiet(containinglotsofsaturatedfat)canleadtohighercholesterol
levels and this cholesterol forms the fatty deposits
whichdamageandblockthearteries.
Smoking–chemicalsincigarettesmoke,includingnicotineandcarbonmonoxide,
increasetheriskofheartdisease.Carbonmonoxidereducestheamountofoxygenwhichcanbetransportedbytheredbloodcellsandnicotinecausesanincreasedheartrate.Thelackofoxygentotheheartandincreasedpressurecanleadtoheartattacks.
Stress–prolongedexposuretostressorstressfulsituations(suchashighpressurejobs)canleadtohighbloodpressureandanincreasedriskofheartdisease.
Blood
Bloodiscomposedofredbloodcells(erythrocytes),whitebloodcellsandplatelets,allsuspendedwithinaplasma(atissue).
Theplasmatransportsthedifferentbloodcellsaroundthebodyaswellascarbondioxide,nutrients,ureaandhormones.Italsodistributestheheatthroughoutthebody.
Red blood cellstransportoxygenattachedtothe
haemgroupintheirstructure.Ithasabiconcaveshapetoincreasesurfaceareaanddoesnotcontainanucleussoitcanbindwithmoreoxygenmolecules.
White blood cells form part of the immune system and ingest
pathogensand produce antibodies. Platelets are important blood
clotting factors.
at the lungshaemoglobin+oxygenoxyhaemoglobin
at the cells
Theright atriumreceivesdeoxygenatedbloodviathevena cava. It is
then pumped down through the valvesinto the right ventricle. From
here, it is forced upthrough the pulmonary artery towards the lungs
where it exchanges carbon dioxide for oxygen. The oxygenated blood
then enters the left atrium via thepulmonary vein and down into the
left ventricle. Themuscularwalloftheleft
ventricleismuchthickersoitcanpumpthebloodmoreforcefullyoutoftheheartandaroundtheentirebody,viatheaorta.
Thebloodonlyflowsinone direction.Thisisbecausethereare valves in
the heart which close under pressure
andpreventthebackwardflowofblood.
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AQA GCSE Biology (Combined Science) Unit 2: Organisation
Cancer
Cancer is the result of uncontrolled cell growth and division.
Theuncontrolledgrowthofcellsiscalledatumour.
Plant Tissues, Organs and Systems
Leaves are plant organs and their main function is to absorb
sunlightenergyforuseinphotosynthesis.Withinthecellsaresmallorganellescalledchloroplastswhichcontainagreenpigmentcalledchlorophyll.This
is
thepartoftheplantwhichabsorbsthesunlightandwherephotosynthesisoccurs.
sunlightcarbondioxide+water oxygen+glucose
Leavesareadaptedtocarryouttheirfunction.Leavesaretypicallyflatandthinwith
a large surface area. Thismeans theyhave amaximumarea
toabsorbthesunlightandcarbondioxide.Thethinshapereducesthedistancefordiffusionofwaterandgases.
Leavescontainvesselscalledxylemandphloem.Thexylemtransportwateranddissolvedmineralstowardtheleaves.Thephloemtransportglucoseandotherproductsfromphotosynthesisaroundtheplant.
The largeair spacesbetweenthecellsof thespongymesophyll
layerallowforthediffusionofgases.Carbon
dioxideenterstheleavesandoxygenexitstheleaves.
Theguard cells
arespeciallyadaptedcellslocatedontheundersideoftheleaf.Theyarepositionedinpairs,surroundingthestomata(asmallopeningintheepidermislayer).Theguardcellschangeshapetoopenandclosethestomata,controllingtherateofgas
exchange intheleaf.
Root Hair Cells
Xylem and Phloem
Rate Calculations for Blood Flow
Thenumberofbeatstheheartperformseachminuteiscalledthepulse(orheartrate).
Itiseasilymeasuredbycountingthenumberofbeatsinagiventime,e.g.15s,andfindingthetotalbeatsper
minute.
Typically,alowerrestingpulserateindicatesagreaterlevelofphysicalfitness.Duringexercise,andforsometimeafter,thepulserateincreaseswhiletheheartisworkingtoprovidemoreoxygentothemuscles.
Cardiac
outputisameasureofthevolumeofbloodpumpedbythehearteachminute.Stroke
volumeisameasureofthevolumeofbloodpumpedfromthehearteachcontraction(heartbeat).
Cardiacoutput(cm³/min)=heartrate(bpm)×strokevolume(cm³/beat)
Benign Tumour Malignant Tumour
• Usuallygrowsslowly.
• Usuallygrowswithinamembraneandcanbeeasilyremoved.
• Doesnotnormallygrowback.
• Doesnotspreadaroundthebody.
• Cancausedamagetoorgansandbelife-threatening.
• cancerous
• Usuallygrowsrapidly.
• Canspreadaroundthebody,viathebloodstream.
•
Cellscanbreakawayandcausesecondarytumourstogrowinotherareasofthebody(metastasis).
waxycuticle
spongymesophyll
palisadelayer
lowerepidermis
upperepidermis
guardcells
xylem
stomata
Plantsabsorbwaterbyosmosisthroughtheroothaircellsoftheroots.Dissolvedinthewaterareimportantmineralsforthe
plant’s growth and development,whichareabsorbedbyactive
transport.
Theroot hair
cellsareadaptedtotheirfunctionwiththefollowingfeatures:
• Finger-likeprojectioninthemembraneincreasesthesurface area
availableforwaterandmineralstobeabsorbedacross.
• Thenarrow shape of theprojection can squeeze into
smallspacesbetweensoilparticles,bringingitcloserandreducingthedistanceofthediffusion
pathway.
•
Thecellhasmanymitochondria,whichreleaseenergyrequiredfortheactivetransportofsomesubstances.
Xylemvesselstransportwaterthroughthe plant, from roots to
leaves. They are made up of dead, lignifiedcells, which are joined
end to
endwithnowallsbetweenthem,formingalongcentraltubedownthemiddle.The
movement of the water,
anddissolvedminerals,alongthexylemisinatranspirationstream.
Xylemvesselsalsoprovide support and strength to
theplantstructure. They are found in the middle of roots so
theyaren’t crushedwithin the soil. They are found in themiddleof
the stem to provide strength and prevent bending. In theleaves,
they are found in vascular bundles alongside thephloem and can be
seen as the veins which network across theleaf.
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AQA GCSE Biology (Combined Science) Unit 2: Organisation Phloem
vessels transport food such as dissolved sugars and glucose
fromphotosynthesis. The food is
transportedaroundtheplanttowheregrowthisoccurring
(rootandshoottips),aswellastotheorganswhich store the food. The
transport occursin all directions throughout the plant. The cells
making up the phloem tube are
living,withsmallholesinthewallswherethecellsarejoined.
Transpiration and Translocation
Transpiration is the loss of water, by evaporation and
diffusion,
fromtheleavesoftheplant.Waterisacohesivemoleculeandasitevaporates,thereislesswaterintheleaf,sowaterfromfurtherbackmovesuptotakeitsplace.This,inturn,drawsmorewaterwithit.Thisisthetranspiration
stream.Transpiration occursnaturally as there is a tendency
forwater to
diffusefromtheleaves(wheretheconcentrationisrelativelyhigh)totheairaroundtheplants(wheretheconcentrationisrelativelylow),viathestomata.
Environmental
factorscanchangetherateatwhichtranspirationoccurs:• Increasedlight
intensitywillincreasetherateoftranspirationbecauselightstimulatesthestomatatoopen.Theleafwillalsobewarmedbythesunlight.
•
Increasedtemperaturewillcausethewatertoevaporatemorequicklyandsoincreasetherateoftranspiration.
• Increased humidity (moisture in the air) will reduce the rate
oftranspiration. Whereas if the air becomes drier, the rate
increases.
Agreaterconcentrationgradientwillincreasetherateofdiffusion.
• Ifthewind
speedincreases,thentherateoftranspirationalsoincreases.Thisisbecauseasthewatersurroundingtheleavesismovedawaymorequickly,theconcentrationgradientisincreased.
• Ifthe water content
inthesoilisdecreased,thentherateofabsorptionintherootsdecreases.Thiscausesthestomatatobecomeflaccidandclose,reducingtranspiration.Ifthelossofturgoraffectsthewholeplant,thenitwillwilt.
Health and Disease
Health is thestateofbeing free from illnessordisease.
Itreferstophysicalandmentalwellbeing.
Disease and lifestyle factors, such as diet, stress,
smoking,alcohol consumption and the use of illegal drugs, can
allimpactthehealthofaperson.
Someconditionsareassociatedwithcertainlifestylechoices:
•
Liverconditionsareassociatedwithpoordietandprolongedexcessivealcoholconsumption.
• Lungcancerisassociatedwithsmoking.
• Memory loss, poor physical health and hygiene are
associatedwiththeuseofillegalorrecreationaldrugs.
• Obesityanddiabetesareassociatedwithpoordiet.
• Anxiety and depression are associated with stress
andprolongedexcessivealcoholconsumption.
Disease Interactions
Havingonetypeofillnesscanoftenmakeapersonmoresusceptibletoanothertypeofillness:
• immunedisordersincreasedriskofinfectiousdisease
• viralinfectionofcellsincreasedriskofcancer
• immunereactionscantriggerallergies
•
verypoorphysicalhealthincreasedriskofdepressionorothermentalillness
Therecanoftenbecorrelationsbetweensomefactorsandtypesofillnessorspecificdiseases.
Forexample,inthegraphshowntotheright,thereisapositivecorrelationbetweenthenumberofcigarettessmokedandthenumberoflungcancerdeaths.
However,thereareotherfactorswhichcancontributetothedevelopmentoflungcancere.g.workingwithasbestos,geneticpredisposition.
Thismeansthatalthoughtheevidence inthegraphgivesastrong
indication thatsmoking isacauseoflung cancer, it cannot be stated
that ‘smoking will cause lung cancer’. Not every person who
smokeswill develop lung cancer and not every
personwhodevelopslungcancerwillbeasmoker.
Therefore,itcanbestatedthatsmoking increases the risk of lung
cancer.
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AQA GCSE Biology (Combined Science) Unit 2: Organisation
Heart Disease (Treatments)
Therearearangeofmedicaltreatmentsforheartdisease.
Treatment Description Advantages Disadvantages
statins Drugsused to lower cholesterol levels in theblood,
byreducingtheamountproducedintheliver.
• Canbeusedtopreventheartdiseasedeveloping.
• Improvedqualityoflife.
• Long-termtreatment.
• Possiblenegativeside-effects.
stents Mechanical
devicewhichisusedtostretchnarroworblockedarteries,restoringbloodflow.
• Usedforpatientswheredrugsarelesseffective.
• Offerslong-termbenefits.
• Madefrommetalalloyssowillnotberejectedbythepatientsbody.
• Improvedqualityoflife.
•
Requiressurgeryundergeneralanaesthetic,whichcarriesriskofinfection.
heart transplant
Theentireorganisreplacedwithonefromanorgandonor(apersonwhohasdiedandpreviouslyexpressedawishfortheirorganstobeusedinthisway).
• Cantreatcompleteheartfailureinaperson.
• extendedlife
• Improvedqualityoflife.
•
Artificialplasticheartscanbeusedtemporarilyuntiladonorisfound.
•
Requiresmajorsurgeryundergeneralanaesthetic,whichcarriesrisks.
• Lackofdonorsavailable.
• Riskofinfectionortransplantrejection.
• Longrecoverytimes.
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