enzyme structure and function: comparing student...

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EnzymeStructureandFunction:ComparingStudentResponsestoMultipleQuestionVersions

TannerFoster,KevinHaudek,RosaMoscarella,RachelYoho,MarkUrban-Lurain,JohnMerrillAutomatedAnalysisofConstructedResponse(AACR)ResearchGroup

www.msu.edu/~aacrWHATDOESAACRDO?

WHYISENZYMEBINDINGIMPORTANT?

WHYCONSTRUCTEDRESPONSE(CR)?

EXPLORATORYANALYSISOFQUESTIONVERSIONS

TEXTBOOKINFLUENCES

EXPERTRESPONSEVS.STUDENTANSWERS

WHAT'SNEXT?

• OurresearchgroupfollowswhatwecallaQuestionDevelopmentCycle(QDC).

• Ourresearchquestionsaredesignedbasedonthediscipline'sbigideas,coreconcepts,ofconceptinventories.

• Theultimategoalistocreatemodelsthatcanpredictthehumanscore.

• Structureandfunctionisoneof5coreconceptsforBiologicalLiteracyasstatedbyVisionandChangeinUndergraduateBiologicalEducation.

• Thisconceptisdifficultformanystudents,andinstructorsaffiliatedwiththeprojectareinterestedinexploringstudentideas.

ConstructedResponseallowsstudentsto:• Expresswhattheyknowintheirownwords(KuechlerandSimkin,2010)

• Highlightmisconceptionstheymayhave.• Informinstructorsofwhatstudentsdoanddonotunderstand(BirenbaumandTatsouka,1987)

Version1(n=48)Enzymeshelpchemicalreactionsinlivingorganisms.Howwouldamolecularbiologistexplainhowanenzymemoleculebindstoitscorrectsubstrateandreducesthepossibility ofincorrectinteractions?

Version2(n=48)Enzymeshelpinchemicalreactionsinlivingorganisms.Howwouldamolecularbiologistexplainthemechanismthathelpsanenzymetobindtoitscorrectsubstrateandreducesthepossibility ofincorrectinteractions?

Version3(n=51)Enzymeshelpinchemicalreactionsinlivingorganisms.Therearethousandsofdifferentmoleculesinacell.Howwouldamolecularbiologistexplainthemechanismthatallowsanenzymetobindtoacorrectmolecule?

References:AmericanAssociationfortheAdvancementofScience.(2011).Visionandchangeinundergraduatebiologyeducation:acalltoaction. Washington,DC.Birenbaum,M.,&Tatsouka,K.K.(1987).Open-endedversusmultiple-choiceresponseformats- Itdoesmakeadifferencefordiagnosticpurposes.AppliedPsychologicalMeasurement,11,329-341.Freeman,etal. BiologicalScience. 6thed. 2017.Kuechler,W.L.,&Simkin,M.G.(2010).Whyisperformanceonmultiple-choicetestsandconstructed-responsetestsnotmorecloselyrelated?Theoryandanempiricaltest.DecisionSciencesJournalofInnovativeEducation,8(1),55-73.Mason,etal. UnderstandingBiology. 1sted. 2014.Acknowledgements:ThismaterialisbaseduponworksupportedbytheNationalScienceFoundation(DUEgrants1323162,1347740).Anyopinions,findingsandconclusionsorrecommendationsexpressedinthismaterialarethoseoftheauthor(s)anddonotnecessarilyreflecttheviewsofthesupportingagencies.

• Presentquestionstolargersamplesizeofstudentsinsimilarcourses.

• Analyzeresponsestodeterminebestquestionversion(s).• Investigateifclasslevelaffectsresponsevariability.• Beginrubricdevelopment.

AACRIIICOLLABORATINGINSTITUTIONSFreeman:“Giventhatanenzyme’sstructureiscriticaltoitsfunction,it’snotsurprisingthatanenzyme’sactivityissensitivetoconditionsthatalterproteinshape.”(182)

Mason:“Bybringingtwosubstratestogetherinthecorrectorientationorbystressingparticularchemicalbondsofasubstrate,anenzymelowerstheactivationenergyrequiredfornewbondstoform.Thereactionthusproceedsmuchmorequicklythanitwouldwithouttheenzyme”(122)

Instructorsagreedthatanexpertlevelanswerwouldinclude:• Threedimensionalshapeofthemolecules• Mentionofchemicalpropertiesaffectingbinding• Energeticaspectstatingthecorrectinteractionsaremost

favorableBelowareexamplesofstudentanswers:Enzymeshaveaspecific"lockandkey"structurewhichisspecificforthatmolecule.Itmakessurethatwhentheenzymebinds,itfitsintothestructureandthenchangesthemolecule'sstructuretomakesurenothingelsebindsonit.

Thesubstratecanbindtotheenzymebyhydrogenorcovalentbinding.Toreducethepossibilityofincorrectinteractionstheenzymehasaspecificshapethatallowsforbindingtoaspecificsubstrate.

Therearetwomainmechanismsforenzymebinding.Oneisinducedfit,wherethesubstratechangestheconformationoftheenzymesoitcanbind.Theotheristhelockandkeymodel,inwhichthesubstratefitsperfectlyintotheenzyme'sbindingsite.Enzymesalsohavedifferentaffinitiesfordifferentsubstrates.

Thesethreequestionversionswereaskedaspost-instructionhomeworkinanupperlevelBiochemistryatalargeMidwestern

ResearchUniversity.

Wefoundthatstudentsrespondedsimilarlytoeachquestionversion.However,theirresponsesweremostlybasedonthethee-dimensionalstructureofmoleculesratherthanontheenergeticsoftheirinteraction.