ìMetabolismAPBiologyChapter8
ìEnergy
Energymanagement
ì Bioenergetics isthestudyofhoworganismsmanagetheirenergyresources.
ìEnergy isthecapacitytodowork.ìEnergyexistsinvariousformsìCellstransformenergyfromonetypeintoanother.
Kineticenergy
• Kineticenergy istheenergyassociatedwiththerelativemotionofobjects.
• Objectsinmotioncanperformworkbyimpartingmotiontoothermatter.• Newton’sCradle• Photonsoflightcanbecapturedandtheirenergy
harnessedtopowerphotosynthesisingreenplants.• Heat orthermalenergy iskineticenergyassociated
withtherandommovementofatomsormolecules.
Potentialenergy
ì Potentialenergy istheenergythatmatterpossessesbecauseofitslocationorstructure.ì Chemicalenergy isaformofpotentialenergystored
inmoleculesbecauseofthearrangementoftheiratoms.
Learning Check
ì WhichstatementdoesNOTdescribechemicalenergy?ì Theenergyrequiredbychemicalsì Atypeofpotentialenergyì Theenergystoredinthebondsofthemoleculeì Storedenergythatcanbeusedtodowork
Learning Check
ì Whatisthemostgeneraldefinitionofenergy?ì Heatì Thecapacitytodoworkì Themotionofmoleculesì Sunlight
Learning Check
ì Whichofthefollowingisanexampleofpotentialenergy?ì Heatì Lightì ChemicalEnergyì Allofthesearecorrect
The energy transformations of life are subject to laws of thermodynamics
ì Thermodynamics isthestudyofenergytransformations
ì Inthisfield,thetermsystem referstothematterunderstudyandthesurroundings includeeverythingoutsidethesystem.
ì Aclosedsystem isisolatedfromitssurroundings.ì Inanopensystem, energyandmattercanbe
transferredbetweenthesystemanditssurroundings.
Types of Systems
MatterExchanged?
EnergyExchanged?
Open Yes YesClosed No YesIsolated No No
Opensystems
ì Organismsareopensystems.
ì Theyabsorbenergy(lightorchemicalenergyintheformoforganicmolecules)andreleaseheatandmetabolicwasteproducts(suchasureaorCO2 )totheirsurroundings.
Firstlawofthermodynamics
ì Energycanbetransferredandtransformed,butitcannotbecreatedordestroyed.
ì LawofConservationofEnergy.
ì Energyoftheuniverseisconstant
2nd Law of Thermodynamics
• EverytransformationresultsinareductionoftheFREEENERGY(useableenergy).
• EnergytransfersandtransformationsincreaseENTROPY(disorder,randomnessorchaos).
• LawofEntropy.
• Energyalwaystendstogofromamoreusable(higherquality)formtoalessusable(lowerquality)form.
•Mostconversionsarelessthan100%efficientandthereforesomeenergyislostorwasted.•EnergyislostintheformofHEAT (randomenergyofmolecularmovement).
Solarenergy
Wasteheat
Chemicalenergy
(photosynthesis)
Wasteheat
Wasteheat
Wasteheat
Chemicalenergy(food)
Mechanicalenergy(moving,thinking,living)
Only25%ofchemicalenergystoredingasolineistransformedintomotionofthecarand75%islostasheat!!
Withoutaddingenergytoasystem,thesystemwillbreakdown.
Learning Check
ì Thetransformationofenergyalwaysresultsinthelossofsomeenergyintheformof:ì ATPì ChemicalEnergyì Heatì Light
Learning Check
ì Imagineaglassbox(terrarium)containinglivingplantsandanimalsandsittingonawindowsill.Thegrowthoftheplantsprovidesfoodforsnails,insects,fungi,andbacteriathatliveinthebox.Ventsallowgoodaircirculation.Whatwillhappenifyouputablackclothoverthebox,cuttingoffalllight?
Spontaneousprocesses
• Foraprocesstooccuronitsown,withoutoutsidehelpintheformofenergyinput,itmustincreasetheentropyoftheuniverse.
• Thewordspontaneous describesaprocessthatcanoccurwithoutaninputofenergy.
• Spontaneousprocessesneednotoccurquickly.– Somespontaneousprocessesareinstantaneous,
suchasanexplosion.Someareveryslow,suchastherustingofanoldcar.
MetabolicDisequilibrium
ì Acellthathasreachedmetabolicequilibriumisdead!
ì Noenergyisavailabletodowork
ì Cellsmaintaindisequilibriumbecausetheyareopensystems.
ì Theconstantflowofmaterialsintoandoutofthecellkeepsmetabolicpathwaysfromeverreachingequilibrium.
ATPPowersCellularWork
ì Acelldoesthreemainkindsofwork:ì Mechanicalwork- thebeatingofcilia,contractionof
musclecells,movementofchromosomesduringcellularreproduction.
ì Transportwork-pumpingofsubstancesacrossmembranesagainstthedirectionofspontaneousmovement.
ì Chemicalwork- drivingendergonicreactionssuchasthesynthesisofpolymersfrommonomers.
EnergyCoupling
ì Cellsmanagetheirenergyresourcestodoworkbyenergycoupling
ì Energyfromanexergonic(givesoffenergy)processisusedtodriveanendergonic(takesinenergy)process
ì Inmostcases,theimmediatesourceofenergytopowercellularworkisATP.
ìATP
ATPì ATP(adenosinetriphosphate) =atypeofnucleotideconsisting
ofthenitrogenousbaseadenine,thesugarribose,andachainofthreephosphategroups.
ATPì Thebondsbetweenphosphategroupscanbebrokenby
hydrolysis.ì ATPà ADP+Pi
ATPcyclingì ATPisarenewableresourcethatcanberegeneratedbythe
additionofaphosphategrouptoADP.
ì RegenerationofATPisanendergonicprocess,requiringaninvestmentofenergy.
ì DG =7.3kcal/mol.
Learning Check
ì HowareATPandADPstructurallydifferent?
ì WhichofthefollowingareexamplesofcellularworkthatrequireATPasasourceofenergy?ì Musclecontractionsì Synthesisofcomplexmoleculesì Activetransportofmaterialsacrossmembranes
Learning Check
ì ATPiscontinuouslybuilttoreplacewhatisconsumedbytheactivitiesofthecell.WhatcanyoupredictaboutareactionthatwouldbuildATPfromADPandP?
ì Woulditreleaseorrequireenergy?
ìMetabolism
Metabolism is an Emergent Property of Life
ì Metabolism:totalityofanorganism’schemicalreactions
ì Chemistryoflifeisorganizedintometabolicpathwaysì Beginswithaspecificmolecule,whichisthenaltered
inaseriesofdefinedstepstoformaspecificproduct.ì Aspecificenzymecatalyzeseachstepofthepathway.
Metabolicpathways
• Catabolicpathwaysreleaseenergybybreakingdown complexmoleculestosimplercompounds.
• Ex:cellularrespiration
• Anabolicpathways consumeenergytobuildcomplicatedmoleculesfromsimplercompounds.
• Ex:Thesynthesisofprotein
• Theenergyreleasedbycatabolicpathwayscanbestoredandthenusedtodriveanabolicpathways.
Learning Check
ì Whichiswhich?
Learning Check
Anabolic Catabolic
CellularRespiration
Photosynthesis
SynthesizeStarchfromGlucose
DigestFoodMolecules
BuildComplexProducts
ReleaseEnergy
RequiresEnergy
Breakdowncomplex molecules
Learning Check
ì Putinthecorrectorderì AnabolicReactionì CatabolicReactionì ATPì ADP+P
Learning Check
ì AnabolicreactionsrequireATP.ButittakesenergytomakeATP.WheredoestheenergyforATPsynthesiscomefrom?