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EdexcelGCEBiologyBiology Human)AdvancedSubsidiary/AdvancedUnit Test1Thursday January 003 MorningTime: hour15minutesMaterials required for examination Items included with questionpapersRuler

Instructions to CandidatesIn the boxes above,write your centrenumber,candidate umber, hepaper eference, oursignature,urname nd nitials. Thepaper eferences shownabove.Check hat you have hebooklet for the correctunit.AnswerALL NINE questionsn the spaces rovided n this booklet.Youranswer o Question shouldbe writtenon the inedpages. f you need o use additional;j , ,rswer heets, ttach hem ooselybut securelynside hiibooklet. -Showall the steps n any calculations ndstate he units. Calculatorsmay be used.Includediagrams n your answerswhere hesearehelpful.Information for CandidatesThemarks or individualquestions ndpartsof questions reshown n roundbrackets: .g. 2).The otalmark for thisquestion aper s 70.Advice to CandidatesYouwill be assessedn your ability to organise ndpresentnformation, deas,descriptionsandarguments learly and ogically, akingaccountof your use of grarnmar, unctuationandspelling.

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N15s09A I||lililllilililil]iltlil||ilililil]N 1 5 5 0 9 A Turn overw850/R6r0l/57570 /10/r6,100Thispublication ayonlybe eproducedn accordanceith Edexcel opyrightolicy. dexcel oundationsa registeredharitv.@2003 dexcel EdexcelSuccesshrough qualifications

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Answer ALL questions n the spacesprovided.The tablebelow refers o the structureof different types of nucleic acids. If the featureis present,place a (l) in the appropriatebox and if the feature is absentplace across x) in the appropriate ox.

Feature DNA mRNACytosinepresentUracil presentPentose ugarpresent

Is singlestranded(Total 4 marks)

Z. Readthrough the following passage boutprotein structure, hen write on the dottedlines he mostappropriateword or wordsto complete he passage.The tertiary structureof a protein dependson its primary and secondarystrucfure.The primary structure s the .. of amino acids,which arejoined togetherby .. . bonds o form a chain. This type ofbond s formedwhen a .... reaction akesplacebetweentwo aminoacids.The chainof aminoacidsmaybe folded nto an alphahelix,held in shape y

bonds.

A numberof different typesof bondshold the tertiary and quaternarystructurein shape.For example,he two peptidechains n insulin areheld togetherbv .. ' bondswhich form between he

of certainaminoacids.

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(Total 6 marks)

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Chromosomes

3. Yeastcells grown tnThe diagrambelow

culturewill divide asexuallyo form a clone of yeastcells.shows hisprocess ccurring.

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(a) Explainwhat is meantby the term clone.

(b) On the diagramof oneof thebe found n thenucleus.

Daushtercel1s

(2)daughterells,draw n the chromosomeshatwould

(1)(c ) Suggestwo advantagesf asexualeproductiono an organlsm.

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(2)btal 5 marks

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4 . The diagram below representssoffre of theproductionof the enzymeproteaseor use n the stages nvolved in the commercialmanufacture f a biologicaldetergent.

(a) Explain why proteases re ncorporatednto biologicaldetergents.

(3)

Bacterialcellsgrown n culture

Protease roduced y bacteriaandsecretednto culture luid

Bacterialcells filtered off and discarded

Protease urified

Proteasencorporatednto granules

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(b) The bacteriaused n this probessnormally live in hot water springs where thetemperaturetaysabove45'C.Suggestwo reasons hy it is anadvantageo use heenzymesrom thesebacteriain the detergents.

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(c) When hegranules ontaining he protease ome nto contactwith water heyswelland releaseheircontents.Suggestwhy the enzymes re ncorporatedntoof biologicaldetergents. granulesduring the manufacfure

(2)(Total7 marks)

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5. The diagrambelow sllmmariseshe steps nvolved n the semi-conservativeeplicationof DNA.

Double strandof DNAStepI EnzymeA

Two strandsseparatedStep2

Complernentaryucleotidesine up againsteachstrandStep3 EnzvmeB

Nucleotidesoin to form two new polynucleotide hainsStep4

Two identicalDNA moleculesormed(a) Describehow EnzymeA separateshe two DNA strandsn Step1.

(1)

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(b) In Step 3 the individual nucleotidesare oined up to forrn a polynucleotidechainby Enzyme B.Name the type of reaction hat EnzymeB catalyses.

(c) Give thephaseof the cell cycle during which DNA replicationoccurs.

(1)(d) Draw and abel a diagram o show the appearancef a chlomosomeas t appears

in metaphase f mitosis.

(3)(Total6 marks)

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n// \( (d) J\ )A6. The diagrambelow shows he structure f the cell surfacemetnbrane.

(a) The cell surfacemembranes composedof a phospholipidbilayer. Explainwhythe phospholipids n the bilayer are anangedwith the fatty acid tails pointinginwardsand he phosphate eadsoutwards.

(3)(b) The diagramhasbeenmagnified hree nillion (3 x 106)imes. Calculatehe widthof the cell surfacemembranen pm (micrometres).Showyour working.

Glycopr",.,"ltCarbohydrate Ranndilmnuuuuuuuu

N15509A

Answer

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(c) State one function of each of the following componentsof the cell surfacemembrane.CarbohydrateProtein (2)

(Total 8 marks)

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7. Somebacteriawere grown in a culturewith radioactiveamino acids. They used helabelledamino acids o synthesiseroteinswhich were ncorporatednto their cells.The bacteriawere then washed horoughlyand mixed with somewhite blood cells.The arnount of radioactivity taken up by the white blood cells was lneasuredatintervalsof two hours for 24 hours.Thewhite bloodcellswerephagocytic ndengulfed tookup) the bacteria y aprocesscalledphagocytosis.Piragocytosiss a fonn of endocytosis.This processs illustratedin the diagram below.

lnL

--->

White blood cellLysosomeshen tise with thephagosome ndreleaseheir contentsnto it .The tablebelow shows he level of radioactivity ound inside andoutside he whiteblood cells during the24 hourperiod.

Bacteriu Phagosorne(phagocytic acuole)Membrane xtensrons

oo o o oo o

o tllai,'],t:i;$i;jri/ - oo o o i / o o s o

o o o o o

Nucleus

o o \i'sjflz oo o o l f

A -( o o o o

o tr"ffi;#.H#Y - oo o o f / o o o o

o 9 o o o

Time aftermixing cellstogether/hours Radioactivitynsidewhitebloodcells arbttram'units

Radioactivityoutsidewhiteblood cells arbttraryunits02468

1 01 21 4T61 8202224

01 6486 T7012727 I432 T1 085

8064321 91 0889

a F ,J I59707275

N 1 5094 l 0

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(a) (i) Describe he structure f a lysosome. Leaveblank

(2)(ii) Describehe rolesof lysosomes.

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(b) Describe he changes n the level of radioactivitycellsduringtheperiodof 24 hours.

(2)found nside he whiteblood

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(3)

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(c) Suggestwhat is happeningo the bacteria nside hephagosomesetween 0 and14 hours.

(1)Explain why the amountof radioactivity ncreases utside he white blood cellsafter 14 hours.

(e) Suggestwhy the white blood cells did not takeup all the radioactivity.

(1)(Total11marks)

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(d)

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8. The rate of an enzyme-catalysedeactioncanbe alteredby thepresence f an nhibitor.An investigationwas caffied out into the effect of an inhibitor on enzymeactivity inbarley root tips. Enzyme activity was measuredby finding the rate at which oxygenwasusedby the root tips.Several rolrpsof students arriedout experimentsn which the volumeof oxygenusedby root tips of barleyseedlings as measured vera periodof 2 hours.Each$oup of students sed50 root tips fiom seedlings f the sameage. Thesewereplaced n the samevolumeof a pH 6.5 bufter solutionand kept at 30 oC.After 2 hours, he samevolumeof a 1% solutionof an nhibitorwasadded o eachsetof root tips. The students ontinuedo record he volumeof oxygenused or a furtherhour.The resultsare shown n the graphbelow.

6Total 5volume ofoxygenused 4(arbitrary units)

aJ

2.0 2.5Time hours

3.0

(a) Compare he enzymeactivity during the first two hours of the experimentwith theactivifv after the inhibitor was added.

(2)

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(b) The inhibitor used n this experimentwas a non-activesite-directed nhibitor.Explain what is meantby non-activesite-directed nhibition.

iii(. ) Suggestwhateffect ncreasinghe concentration f the nhibitor mighthaveon therate at which oxygen was used by the root tips. Give an explanation or youranswer.

(2)(d) Suggestwhy readingswere taken for 2 hours before the inhibitor was added.

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(e ) Suggestwhy the root tips were kept atinvestigation.

(1)a temperature f 30oCthroughout his

(2)

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(0 Explainwhy a buffer solutionwas used n this experiment. Leaveblanlc

(e) Strggest ne reasonvary.(2)

different roups f students ighthv the results fi'om the

(1)(Total13marks)

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9. Give an accountof the structureand function of the polysaccharid.esellulose,starchandglycogen.

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(Total 10 marks)

ENDTOTAL FOR PAPER:70 MARKS