aqa gcse biology (combined science) unit 2: organisation · aqa gcse biology (combined science)...

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

visit twinkl.comPage 1 of 6

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.

visit twinkl.comPage 2 of 6

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.

visit twinkl.comPage 3 of 6

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.

visit twinkl.comPage 4 of 6

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.

visit twinkl.comPage 5 of 6

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.

visit twinkl.comPage 6 of 6