生物化学试题标准答案(2005秋季,A卷).doc

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1、中山大学生命科学学院试卷051.Withregardtoaminoacids,whichstatementisfalse?A)Aminoacidscanactasprotondonorsandacceptors.B)AllaminoacidsdiscoveredinorganismareLenantiomers.C)AnLaminoacidcanbeDextrorotary.D)Non-standardaminoacidscanbefoundinthehydrolysisproductofaprotein.2.Inahighlyacidicsolution,pH=1.3,th

2、edominantformofglycineis:A)NH2-CH2-COOH；B)NH3+-CH2-COOH；C)NH2-CH2-COO–；D)NH3+-CH2-COO–.3.Intheisoelectricformofatetrapeptide:A)Theaminoandcarboxylterminiarenotcharged.B)TwointernalaminoacidsofthetetrapeptidecannothaveionizableRgroups.C)Thetotalnetchargeiszero.D)Onlytheaminoandcarboxyltermin

3、icontributecharge.4.Whichwouldelutefirstfromagel-exclusionchromatographiccolumn?A)anegativelychargedproteinofMW=40,000B)apositivelychargedproteinofMW=40,000C)aproteinatitsisoelectricpointofMW=30,000D)apolysaccharideofMW=100,0005.Inanaqueoussolution,proteinconformationisdeterminedbytwomajorf

4、actors.Oneistheformationofthemaximumnumberofhydrogenbonds.Theotheristhe:A)formationofthemaximumnumberofhydrophilicinteractions.B)maximizationofionicinteractions.C)minimizationofentropybyformingawatersolventshellaroundtheprotein.D)placementofallhydrophobicaminoacidresidueswithintheinteriorof

5、theprotein.6.YoucandestabilizeaduplexDNAmoleculeinanaqueoussolutionbyA)Decreasingtheconcentrationofsalt.B)Decreasingtheconcentrationoforganicsolvents.C)AdjustingthepHtoavaluenear7.D)Addingadetergent.7.WithregardtoDNA,whichstatementisfalse?A)Triplehelixandtetraplextendtoappearatsiteswhererep

6、lication,recombinationortranscriptionisinitiatedorregulated.B)HydrogenbondsaretheonlyforcetostabilizeDNAstructure.C)TheabsorbanceofDNAat260nmwillrisewhenitisdenatured.D)Z-DNAtractsmayplayanroleintheregulationoftheexpressionofsomegenesoringeneticrecombination.7中山大学生命科学学院试卷8.Thrand/orLeuresid

7、uestendtodisruptanahelixwhentheyoccurnexttoeachotherinaproteinbecause:A)ofelectrostaticrepulsionbetweentheThrand/orLeusidechains.B)bothaminoacidsarehighlyhydrophobic.C)theRgroupofneitheraminoacidcanformahydrogenbond.D)ofsterichindrancebetweenthebulkyThra