buffers - george mason university：缓冲区-乔治梅森大学

《buffers - george mason university：缓冲区-乔治梅森大学》由会员上传分享，免费在线阅读，更多相关内容在应用文档-天天文库。

1、BuffersSafetyPrecautionsSafetygogglesandglovesmustbewornatalltimesduringthisexperiment.Wewillbeusingstrongacidsandbaseswhichcancausesevereburnsandeyeinjuries;therefore,payattentiontohowyouhandlecontainersandhowyouaddandmixdifferentreagents.Washcontaminatedareaswithcoldwater.Reportanyspillstothe

2、instructor.BackgroundInformationBiochemicalprocessesonmolecularorcellularlevelsdependonstrictregulationofthehydrogenionconcentration.TheactivityofdifferentenzymesinourbodyvariesgreatlyasthepHoftheenvironmentchanges.Thenaturalconformationofmostbiomoleculesisafactorofextracellularorintracellularp

3、H.SignificantvariationsinpHcanresultinreversibleandirreversibledenaturationandinactivationofproteins.Therefore,toachieveoptimalcellularactivitythepHmustbekeptataconstantvalue.Thisisassuredbythepresenceofnaturallyoccurringbuffers.ThesebuffershavetheabilitytoresistpHchangesbasedontheirpKavalues.A

4、bufferconsistsofaweakacidinequilibriumwithitsconjugatebase.Therefore,ifanacidicagentisintroducedintotheenvironment,theprotonsreleasedbytheacidaretakenupbytheconjugatebaseandnodropinpHisobserved.Ifabasicagentisaddedtotheenvironment,theadditionalhydroxideionsareneutralizedbytheweakacid,thusthepHi

5、snotincreased.ThestorystandsuntiltheamountofH+orOH-addedtothesolutionovercomestheweakacidandbaseofthebuffer.Oncealltheweakacidandweakbaseareconsumedduetotheadditionofbaseoracidrespectively,thebufferingcapacityislost.Thebufferingsysteminourbloodstreaminvolvescarbonicacid/bicarbonateandCO2reactin

6、ginaclosedsystem.Experimentally,itisdifficulttousethisbufferingsysteminthelabduetothelossofCO2totheenvironment,whichinturnresultsinlossofbufferingcapacity.Inexperimentalanalysis,bufferssuchasHEPES(pKa=7.55),whicharecompatiblewiththenaturalbuffersinthebody,areusedtomimicthecellularenvironment.An

7、otherdifficultyinchoosingtherightbufferforabiochemicalexperimentisprovidingtherightconditionsunderwhichthebufferisexpectedtofunctionsuchastheconcentration,salteffect,andtemperatureofthesolution.Itisalsoimportanttokeepinmindthatsom