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