SOLUTIONS
FinalTest:EDEXCELADDITIONALSCIENCEBiology–Enzymes(15marks)
1. Whatisthepartofanenzymethatthesubstratebindsto?(circlethecorrectanswer)
A.
Activesite
B.
Aminoacids
C.Adenine
D.
Substrates
(1mark)
2. Completethesentenceswiththewordsintheboxbelow;thewordsmaybeusedonce,morethanonceor
notatall.
shape optimum increase
denatured
bigger
Increase
Temperatureaffectstherateofenzymeactivity.Whenyou……………..thetemperature
Optimum
therateofenzymeactivityincreasesuntilitreachesthe………………………..temperature.
Shape
Pastthispointthe…………………..oftheactivesitecanchangeandthiscausesthe
Denatured
enzymetobecome…………………………..Itwillnolongerwork.
(3marks)
3. DigestiveenzymessuchasproteasesfoundinthestomachworkbestatpH2.Whatwouldhappentothe
enzymesiftheyareplacedinalkalineconditions?
Theshapeoftheactivesitewouldchange.(1)
Substrates/proteinswillnolongerbind.(1)
Enzymeactivitywilldecrease/enzymewillnolongerwork.(1)
(3marks)
4. Stateonewaythatproteinsandenzymesaresimilarandonewaythatproteinsandenzymesaredifferent.
Proteinsandenzymesaremadefromaminoacids.(1)
Enzymescatalysereactionswhereasnotallproteinsdo.(1)
(2marks)
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SOLUTIONS
5.QWC:
Thequalityofwrittencommunicationwillbeassessedinyouranswertothisquestion.
Explainhowenzymesspeedupchemicalreactions.Youmustdiscussthemechanismsenzymesusetospeed
upreactions.
(6marks)
QWCSuggestedmarkingguidance(Total6marks)
MarksawardedforthisanswerwillbedeterminedbytheQualityofWrittenCommunication(QWC)aswellasthe
standardofthescientificresponse.Teachersshouldapplya‘best-fit’approachtothemarking.
0marks
Norelevant
content.
Level1(1-2marks)
Level2(3-4marks)
Level3(5-6marks)
Ananswerwhichdescribes
thatenzymeshaveanactive
siteandsubstratesbindto
theactivesite
Thespelling,punctuation
andgrammararevery
weak.
Adescriptionofspecificitybetween
activesiteandsubstrates
Thereisreasonableaccuracyin
spelling,punctuationandgrammar,
althoughtheremaystillbesome
errors.
Anexplanationofhowthismodel
relatestothelockandkey
mechanismandspeedsup
reactions
Theanswershowsalmostfaultless
spelling,punctuationand
grammar.
Enzymehasaregioncalledanactivesite.
Substratebindstoactivesite.
Activesitespecificshape/specificity.
Soonlyacertain/specificsubstratecanbind.
Othersubstratescannotbindtheydonothavetherightshape.
Thisislikeakeyfittingalock–onlythekeywiththerightshapecanfit.Otherkeyscannotopenthe
lock.
Thiscausesreactionstospeedupastheenzymeslowertheenergyneededforsubstratestoreact.
1
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