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?