MetabolismandEnergyMetabolismandEnergyBIOL222

Ch.8

Overview:TheEnergyofLifeOverview:TheEnergyofLife

• Thelivingcellisaminiaturechemicalfactorywherethousandsofreac?onsoccur

• Thecellextractsenergyandappliesenergytoperformwork

• Someorganismsevenconvertenergytolight,asinbioluminescence

• Lux‐bacteria

• Luciferase‐fireflies

MetabolismMetabolism

• Metabolism

• Thetotalityofanorganism’schemicalreac?ons

• Sumofanabolismandcatabolism

• emergentpropertyoflifethatarisesfrominterac?onsbetween

moleculeswithinthecell

• Butinacontrolledmanner…

• homeostasis

MetabolicPathwaysMetabolicPathways

• Metabolicpathway

• beginswithaspecific

moleculeandendswith

aproduct

• Eachstepiscatalyzed

byaspecificenzyme

Fig.8‐UN1Fig.8‐UN1

Enzyme 1 Enzyme 2 Enzyme 3DCBA

Reaction 1 Reaction 3Reaction 2Startingmolecule

Product

• Catabolicpathways

• Releaseenergybybreakingdowncomplexmoleculesinto

simplercompounds

• Cellularrespira?on

• Thebreakdownofglucoseinthepresenceofoxygen

• isanexampleofapathwayofcatabolism

CatabolismCatabolism

• Anabolicpathways

• consumeenergytobuildcomplexmoleculesfromsimplerones

• Thesynthesisofproteinfromaminoacids

• Bioenerge?cs

• Thestudyofhoworganismsmanagetheirenergyresources

• Alllifeboilsdowntoenergybudget

AnabolismAnabolism

• Kine?cenergy

• energyassociatedwithmo?on

• Heat(thermalenergy)

• kine?cenergyassociatedwithrandommovementofatomsor

molecules

• Poten?alenergy

• energythatmaSerpossessesbecauseofitsloca?onorstructure

• Chemicalenergy

• poten?alenergyavailableforreleaseinachemicalreac?on

• Energycanbeconvertedfromoneformtoanother

TypesofEnergyTypesofEnergy

Fig.8‐2Fig.8‐2

Climbing up converts the kineticenergy of muscle movementto potential energy.

A diver has less potentialenergy in the waterthan on the platform.

Diving convertspotential energy tokinetic energy.

A diver has more potentialenergy on the platformthan in the water.

TheLawsofEnergyTransforma?onTheLawsofEnergyTransforma?on

• Thermodynamics

• Thestudyofenergytransforma?ons

• Closedsystem

• Isolatedfromitssurroundings

• Likeliquidinathermos

• Opensystem

• energyandmaSercanbetransferredbetweenthesystemanditssurroundings

• Organismsareopensystems

TheFirstLawofThermodynamicsTheFirstLawofThermodynamics

• Firstlawofthermodynamics

• Theenergyoftheuniverseisconstant:

–Energycannotbecreatedordestroyedbuttransferredand/ortransformed

• Alsocalledtheprincipleofconserva?onofenergy

TheSecondLawofThermodynamicsTheSecondLawofThermodynamics• Secondlawofthermodynamics:

–Everyenergytransferortransforma5onincreasestheentropy

(disorder)oftheuniverse

• Duringeveryenergytransferortransforma?on,someenergyis

unusable,andisoWenlostasheat

• Increasesentropy

• Livingcellsunavoidablyconvertorganizedformsofenergytoheat

• Spontaneousprocessesoccurwithoutenergyinput;theycanhappen

quicklyorslowly

• Foraprocesstooccurwithoutenergyinput,itmustincreasethe

entropyoftheuniverse

• Generallycorrespondstobreakdown

EnergyEnergy

BiologicalOrderandDisorderBiologicalOrderandDisorder

• Cells

• Createorderedstructuresfromlessorderedmaterials

• Anabolism

• Equalslessentropy

• Requirestheinputofenergy

• Cells

• AlsoreplaceorderedformsofmaSerandenergywithlessordered

forms

• Catabolism

• Energyflowsintoanecosystemintheformoflightandexitsintheformof

heat

• Evolu?on

• Yieldsmorecomplexorganisms

• Doesnotviolatethesecondlawofthermodynamics

• Entropy(disorder)maydecreaseinanorganism

• Theuniverse’stotalentropyincreases

OrganismalOrganismalOrderOrder

Free‐EnergyChange(Free‐EnergyChange(ΔΔG)G)

• Biologistswanttoknowwhichreac?onsoccurspontaneouslyand

whichrequireinputofenergy

• needtodetermineenergychangesthatoccurinchemical

reac?ons

• (Gibbs)Freeenergy

• Alivingsystem’senergyavailabletodoworkwhentemperature

andpressureareuniform

• Enthalpy

• Ameasureofthetotalenergyofathermodynamicsystem

• Freeenergychange

• (∆G):duringachemicalreac?on

• (∆H):Changeinenthalpy(totalenergyinbiologicalsystems)

• (∆S):Changeinentropy(disorder)

• (T):temperatureinKelvin

• ∆G=∆H–T∆S

• Onlyprocesseswithanega?ve∆Garespontaneous

• Spontaneousprocessescanbeharnessedtoperformwork

Free‐EnergyChange(Free‐EnergyChange(ΔΔG)G)

FreeEnergy,Stability,andEquilibriumFreeEnergy,Stability,andEquilibrium

• Freeenergy

• measureofasystem’sinstability,itstendencytochangetoamore

stablestate

• Duringspontaneouschange

• freeenergydecreasesandthestabilityofasystemincreases

• Equilibrium

• stateofmaximumstability

• Lowestenergy

• Aprocessisspontaneousandcanperformworkonlywhenitismoving

towardequilibrium