生物化学试题标准答案(2005秋季,a卷)

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1、1.Withregardtoaminoacids,whichstatementisfalse?A)Aminoacidscanactasprotondonorsandacceptors・回)AllaminoacidsdiscoveredinorganismarcLenantiomers・C)AnLaminoacidcanbeDextrorotary.D)Non-standardaminoacidscanbefoundinthehydrolysisproductofaprotein・2.Inahighlyacidicsolution,pH

2、=1.3,thedominantformofglycineis:A)NH2-CH2-COOH；g)NH3+-CH2-COOH；C)NH2-CH2-COO~；D)NH3+-CH2-COO_.3.Intheisoelectricfonnofatetrapeptide:A)Theaminoandcarboxyltenniniarenotcharged・B)TwointernalaminoacidsofthetetrapeptidecannothaveionizableRgroups・冋)Thetotalnetchargeiszero.D)O

3、nlytheaminoandcarboxyltenninicontributecharge・4.Whichwouldelutefirstfromagel-exclusionchromatographiccolumn?A)anegativelychargedproteinofMW=40,000B)apositivelychargedproteinofMW=40,000C)aproteinatitsisoelectricpointofMW=30,000冋)apolysaccharideofMW=100,0005.Inanaqueousso

4、lution,proteinconfonnationisdetenninedbytwomajorfactors.Oneistheformationofthemaximumnumberofhydrogenbonds.Theotheristhe:A)formationofthemaximumnumberofhydrophilicinteractions・B)maximizationofionicinteractions.[cj)minimizationofentropybyformingawatersolventshellaroundth

5、eprotein.D)placementofallhydrophobicaminoacidresidueswithintheinterioroftheprotein・6.YoucandestabilizeaduplexDNAmoleculeinanaqueoussolutionbyA)Decreasingtheconcentrationofsalt.B)Decreasingtheconcentrationoforganicsolvents.C)AdjustingthepHtoavaluenear7.(D

6、)Addingadeterge

7、nt.7.WithregardtoDNA,whichstatementisfalse?A)Triplehelixandtetraplextendtoappearatsiteswherereplication,recombinationortranscriptionisinitiatedorregulated・回)HydrogenbondsaretheonlyforcetostabilizeDNAstructure.C)TheabsorbanceofDNAat260nmwillrisewhenitisdenatured・D)Z-DNAt

8、ractsmayplayanroleintheregulationoftheexpressionofsomegenesoringenetic1.Withregardtoaminoacids,whichstatementisfalse?A)Aminoacidscanactasprotondonorsandacceptors・回)AllaminoacidsdiscoveredinorganismarcLenantiomers・C)AnLaminoacidcanbeDextrorotary.D)Non-standardaminoacidsc

9、anbefoundinthehydrolysisproductofaprotein・2.Inahighlyacidicsolution,pH=1.3,thedominantformofglycineis:A)NH2-CH