SM_c13BioenergeticsandBiochemicalReactionTypes

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1、c13BioenergeticsandBiochemicalReactionTypes.qxd12/6/124:32PMPageS-142chapterBioenergeticsandBiochemical13ReactionTypes1.EntropyChangesduringEggDevelopmentConsiderasystemconsistingofanegginanincuba-tor.Thewhiteandyolkoftheeggcontainproteins,carbohydrates,andlipids.Iffertilized,theeggistrans

2、formedfromasinglecelltoacomplexorganism.Discussthisirreversibleprocessintermsoftheentropychangesinthesystem,surroundings,anduniverse.Besurethatyoufirstclearlydefinethesystemandsurroundings.AnswerConsiderthedevelopingchickasthesystem.Thenutrients,eggshell,andoutsideworldarethesurroundings.T

3、ransformationofthesinglecellintoachickdrasticallyreducestheentropyofthesystem(increasestheorder).Initially,thepartsoftheeggoutsidetheem-bryo(withinthesurroundings)containcomplexfuelmolecules(alow-entropycondition).Duringincubation,someofthesecomplexmoleculesareconvertedtolargenumbersofCO2a

4、ndH2Omolecules(highentropy).Thisincreaseinentropyofthesurroundingsislargerthanthedecreaseinentropyofthechick(thesystem).Thus,theentropyoftheuniverse(thesystemsurroundings)increases.2.CalculationofGfromanEquilibriumConstantCalculatethestandardfree-energychangeforeachofthefollowingmetabo

5、licallyimportantenzyme-catalyzedreactions,usingtheequilibriumconstantsgivenforthereactionsat25CandpH7.0.aspartateaminotransferase(a)Glutamateoxaloacetateaspartate888888888888zy88888888888a-ketoglutarateKeq6.8triosephosphateisomerase(b)Dihydroxyacetonephosphate888888888888zy88888888888

6、glyceraldehyde3-phosphateKeq0.0475phosphofructokinase(c)Fructose6-phosphateATPfructose8888888y8888888888888888888z81,6-bisphosphateADPKeq254AnswerGGRTln[products]/[reactants]and[products]/[reactants]isthemass-actionratio,Q.Atequilibrium,G0andQKeq,soGRTlnKeqwhereR8.31

7、5J/molKandT25C298K.UsingthevalueRT2.48kJ/mol,wecancalculatetheGvaluesfromtheKeqforeachreaction.(a)G(2.48kJ/mol)ln6.84.8kJ/mol(b)G(2.48kJ/mol)ln0.04757.56kJ/mol(c)G(2.48kJ/mol)ln25413.7kJ/molS-142c13BioenergeticsandBiochemicalReacti