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Lecture 5

BIOL 112 Lecture Notes - Lecture 5: Anabolism, Endergonic Reaction


Department
Biology
Course Code
BIOL 112
Professor
Joseph Dent
Lecture
5

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Metabolism
Canbedividedintotwotypesofacvates:
Anabolicreaconslinksimplemoleculestogethertomakecomplexones.Theyareenergy‐
storingreacons.Theyrequireenergy
Catabolicreaconsbreakdowncomplexmoleculesintosimplerones.Theyreleaseenergy
Cellsmustconstantlyacquireenergyfromtheirenvironment
Energyconversions
Firstlawofthermodynamics:duringanyconversionofenergy,thetotalinialenergy
equalsthetotalfinalenergy.Energyisneithercreatednordestroyed
Nottheenergycontentbutthedriveofenergytobecomeevenlydistributedordispersed
Secondlawofthermodynamics:energyspontaneouslydispersesfrombeinglocalizedto
becomingspreadoutifitisnothinderedfromdoingso(entropyincreases)
Energyconversions,chemicalreaconsonlyoccurifenergydispersesintheuniverse
Thedispersingenergyisthedrivingforceforenergyconversions
Energytransformaonsalwaysresultinastateofhigherprobability(amoredisordered
state)
Tojudgebiochemicalreacons,weneedanequaonthatgivesustheamountofenergy
releasedtodriveareacon(changeinentropyintheuniverse,orfreeenergy)
Cellreleasefreeenergy
Withachemicalreaconcreangdisorderinthecell(digesngapolymer)
Withachemicalreaconreleasingheatwhichgeneratesdisorder/dispersesenergyinthe
surrounding(environment)
TotalFreeEnergy
G=H‐TS
H=enthalpy=heat
S=entropy=disorder
T=absolutetemperature
Wedon’twanttoknowthetotalfreeenergyofamolecule,onlythechangeassociated
withaspecificchemicalreacon
Thischangecanbemeasuredincaloriesorjoules
Freeenergychange:deltaG=deltaH‐TdeltaS
deltaG=Gend‐Gstart
IfdeltaGisnegave,energyisreleased/dispersed(disorderiscreatedintheuniverse)
IfdeltaGisposive,energyisrequired
Onlyfourtypesofreacons
1. Heatisreleaseanddisorderisincreased:alwaysspontaneous(exergonic)
Mostcatabolicreacons
deltaGistheactualamountofenergydispersedduringachemicalreacon
1. Heatisreleased,butdisorderdecreases:onlyspontaneousbelowacertaintemperature
Thisreaconoccursonly(‐deltaG)iftheheatreleasedisgreaterthantheincreasein
order
1. Heatisused,butdisorderincreases:spontaneousaboveacertaintemperature
2. Heatisusedanddisorderdecreases:neverspontaneous(endergonic)
Mostanabolicreacons
ThesedeltaGcalculaonsaregoodforfindingoutwhichreaconscanoccurandwhich
cannot
Exergonicreacons
Spontaneous,deltaGnegave
Cellrespiraon
catabolism
Endergonicreacon
Non‐spontaneous,deltaGposive
Acvetransport
Cellmovements
Energy
February4,2015 9:38AM
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