CHAPTER 2 Water and pH

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1、CHAPTER2:Water&pHPeterJ.Kennelly;VictorW.RodwellINTRODUCTIONOBJECTIVESAfterstudyingthischapter,youshouldbeableto:Describethepropertiesofwaterthataccountforitssurfacetension,viscosity,liquidstateatambienttemperature,andsolventpower.Usestructuralformulastorepre

2、sentseveralorganiccompoundsthatcanserveashydrogenbonddonorsoracceptors.Explaintheroleplayedbyentropyintheorientation,inanaqueousenvironment,ofthepolarandnonpolarregionsofmacromolecules.Indicatethequantitativecontributionsofsaltbridges,hydrophobicinteractions,

3、andvanderWaalsforcestothestabilityofmacromolecules.ExplaintherelationshipofpHtoacidity,alkalinity,andthequantitativedeterminantsthatcharacterizeweakandstrongacids.CalculatetheshiftinpHthataccompaniestheadditionofagivenquantityofacidorbasetothepHofabufferedsol

4、ution.Describewhatbuffersdo,howtheydoit,andtheconditionsunderwhichabufferismosteffectiveunderphysiologicorotherconditions.IllustratehowtheHenderson-HasselbalchequationcanbeusedtocalculatethenetchargeonapolyelectrolyteatagivenpH.BIOMEDICALIMPORTANCEWateristhep

5、redominantchemicalcomponentoflivingorganisms.Itsuniquephysicalproperties,whichincludetheabilitytosolvateawiderangeoforganicandinorganicmolecules,derivefromwater’sdipolarstructureandexceptionalcapacityforforminghydrogenbonds.Themannerinwhichwaterinteractswithaso

6、lvatedbiomoleculeinfluencesthestructurebothofthebiomoleculeandofwateritself.Anexcellentnucleophile,waterisareactantorproductinmanymetabolicreactions.Regulationofwaterbalancedependsuponhypothalamicmechanismsthatcontrolthirst,onantidiuretichormone(ADH),onretentio

7、norexcretionofwaterbythekidneys,andonevaporativeloss.Nephrogenicdiabetesinsipidus,whichinvolvestheinabilitytoconcentrateurineoradjusttosubtlechangesinextracellularfluidosmolarity,resultsfromtheunresponsivenessofrenaltubularosmoreceptorstoADH.Waterhasaslightprop

8、ensitytodissociateintohydroxideionsandprotons.Theconcentrationofprotons,oracidity,ofaqueoussolutionsisgenerallyreportedusingthelogarithmicpHscale.Bicarbonateandotherbuffersn