生物化学试题答案与评分标准(2005秋季，A卷)

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1、中山大学生命科学学院试卷生物化学I标准答案（2005年秋季学期,A卷）专业(班级)：姓名：学号：阅卷教师：题号一二三四五合计分数警示《中山大学授予学士学位工作细则》第六条：“考试作弊不授予学士学位”。一、选择唯一正确答案（每小题1.5分，共15分）1.Withregardtoaminoacids,whichstatementisfalse?A)Aminoacidscanactasprotondonorsandacceptors.B)AllaminoacidsdiscoveredinorganismareLenan

2、tiomers.C)AnLaminoacidcanbeDextrorotary.D)Non-standardaminoacidscanbefoundinthehydrolysisproductofaprotein.2.Inahighlyacidicsolution,pH=1.3,thedominantformofglycineis:A)NH2-CH2-COOH；B)NH3+-CH2-COOH；C)NH2-CH2-CO–；D)NH3+-CH2-COO–.3.Intheisoelectricformofatetrap

3、eptide:A)Theaminoandcarboxylterminiarenotcharged.B)TwointernalaminoacidsofthetetrapeptidecannothaveionizableRgroups.C)Thetotalnetchargeiszero.D)Onlytheaminoandcarboxylterminicontributecharge.4.Whichwouldelutefirstfromagel-exclusionchromatographiccolumn?A)aneg

4、ativelychargedproteinofMW=40,000B)apositivelychargedproteinofMW=40,000C)aproteinatitsisoelectricpointofMW=30,000D)apolysaccharideofMW=100,0005.Inanaqueoussolution,proteinconformationisdeterminedbytwomajorfactors.Oneistheformationofthemaximumnumberofhydrogenbo

5、nds.Theotheristhe:A)formationofthemaximumnumberofhydrophilicinteractions.B)maximizationofionicinteractions.C)minimizationofentropybyformingawatersolventshellaroundtheprotein.D)placementofallhydrophobicaminoacidresidueswithintheinterioroftheprotein.7中山大学生命科学学院

6、试卷6.YoucandestabilizeaduplexDNAmoleculeinanaqueoussolutionbyA)Decreasingtheconcentrationofsalt.B)Decreasingtheconcentrationoforganicsolvents.C)AdjustingthepHtoavaluenear7.D)Addingadetergent.7.WithregardtoDNA,whichstatementisfalse?A)Triplehelixandtetraplextend

7、toappearatsiteswherereplication,recombinationortranscriptionisinitiatedorregulated.B)HydrogenbondsaretheonlyforcetostabilizeDNAstructure.C)TheabsorbanceofDNAat260nmwillrisewhenitisdenatured.D)Z-DNAtractsmayplayanroleintheregulationoftheexpressionofsomegenesor

8、ingeneticrecombination.8.Thrand/orLeuresiduestendtodisruptanahelixwhentheyoccurnexttoeachotherinaproteinbecause:A)ofelectrostaticrepulsionbetweentheThrand/orLeusidechains.B)bothaminoacids