Download LECTURE 9 – 20th March 2015

LECTURE9–20thMarch2015
Energy
-Metabolism=Chemicalandenergytransformationsincells.
-ComplexSystemrequiresenergy.Humansareexampleofcomplexsystem,
whichmeanshumansneedenergytokeepgoing;energybuildsus.
-Energyisconserved.Itisstored.Soifthereischemicalreactionthatliberated
energy,theenergyisgoingtogosomewhere,caneitherbeusedbythecellto
dosomework,ordissipatedasheat;itisnotdestroyed.
βOxidation
- Initialprocessingoflipids
- Lipidshydrolysedintofreefattyacidsandglycerol
- Thefattyacidsarebeingconvertedintomoleculecalled
AcetylCoA
- AcetylCoA=gatewaytothecitricacidcycle
- ProducesFADH2andNADH
HarvestingChemicalEnergy
-ATPisusedtodrivethecellularprocesses
ATP
-Adenineunitwithribosesugarand3phosphategroups
-Thebondsthatholdthephosphategroupsarehigh-energybonds,sowhen
oneofthephosphategroupsisbrokenoff,theenergyreleasedcanbeusedby
celltodosomething.
-Example:SubstrateAbrokendowntoitsproduct,energyisbeingreleased
whichthenusedtostickphosphategroupontoADPtogiveATP,andthen
whenthat’sremovedtheenergycanusedtodrawsomeotherreaction
-Energyreleasedfromanexergonicreaction(energyisreleased)isusedto
phosphorylateADP,whichisthendephosphorylatedtodriveanendergonic
reaction(energyisabsorbed)
EnzymeCatalyticCycle
1.Thesubstrate,sucrose,consistofglucoseandfructosebondedtogether
2.Thesubstratebindstotheenzyme,forminganenzyme-substratecomplex
3.Thebindingofthesubstrateandenzymeplacesstressontheglucosefructosebond,andthebondbreaks
4.Productsarereleaseandtheenzymeisfreetobindothersubstrates.
CellularRespiration
-Breakdownmolecules(mostlyglucose)toproduceenergy
-Glycolysis->TheCitricAcidCycle->ElectronTransport
-Inaerobiccellularrespiration,Oxygenisthefinalelectronacceptorofthe
electrontransportsystem;theenergyreleasedfromreducedelectroncarriers
isusedtocreateaprotongradientacrossthemitochondrialinnermembrane
1.Glycolysis
- Occursinthecytosol
- Initialprocessingofglucose(fuelmoleculesofcells)
- Glycolysisisanetproducerofenergy
- Glycolysisisthefirstchoiceratherthanbetaoxidation
- Acetyl-CoAisproducedbyprocesscalleddecarboxylationofpyruvate
- Forglycolysistocontinue,thecellrequireNAD+
- Startingmaterial=6-carbon-glucose
- Product=2pyruvicacid,2ATP,2NADHand2water
2.TheCitricAcidCycle(KrebsCycle)
- Occursinmatrixmitochondria
- TheoxidationofpyruvatetoAcetyl-CoA
- Theoxidativestepsarecoupledtothereductionofelectron
carriers
- Reducedelectroncarriersareproduced
- Startingmaterial=AcetylCoAand4-carbonmolecule
- Product=2ATP,4CO2,6NADH,2FADH2
- TheconversionofpyruvatetoAcetylCoAresultsinCO2
isproducedandthefirstNADHisformed
- Inthefinalstep,the4-carbonmoleculeisfurtheroxidizedand
hydrogenthatareremovedareusedtoformNADHandFADH2
3.ElectronTransportChain
- Have10NADH,and2FADH2fromglycolysisandKrebscycle
- Occursinthemitochondrialmembrane
- NADHisbeingconvertedbacktoNAD+,anditgoesback
totheKrebsCycle,picksupanothercoupleofelectrons,
runsbackagaintotheElectronTransportChain.
- NADHdehydrogenase=pullsthehydrogenionfrom
NADH(temporaryelectroncarrier)
- Theelectronbeingpasseduptooneenzymescomplextoanother
withaseriesofredoxreaction.Everytimethathappens,itispassed
downwithaslightlydifferentenergystates.Theenergylossisused
topumpthehydrogenionfrommitochondrialmatrixacrossthe
inter-membranespace.
- ElectronsdonatedbyNADHandFADH2fromthecitricacidcycle
driveprotonpumpscoupledtoATPsynthesis
- Produce:6H2Oand26-28ATP
Fermentation
- ATPproductionwithoutoxygen
- Thepyruvateproducedbyglycolysisisconvertedtolactateorethanol
- InvolvesglycolysisthatconsumeNADHproducedinglycolysisfor
reductionofpyruvate
- RecyclesNAD+forreuseinATPproduction
Mitochondria
- Thesiteofcellularrespiration
- Releaseenergybyoxidationofsugars
- ReleaseenergystoredinATP
- Cellswithhighlevelofmetabolicactivityhavelargenumbersof
mitochondria
- Theproteincomplexesoftheelectrontransportsystemofchloroplast
createaprotongradientthatdrivesATPsynthesis
Chemiosmosis
- Movementsofionsacrossaselectivelypermeablemembrane,down
theirelectrochemicalgradient.Morespecifically,itrelatestothe
generationofATPbythemovementofhydrogenionsacrossa
membraneduringcellularrespirationorphotosynthesis.
- ATPisbeingsynthesizeherewithATPSynthase
- TheenergyforthesynthesisofATPduringtheflowofelectronsdown
therespiratorychainisprovideddirectlybythediffusionofprotons
- Protonsarepumpedoutofmitochondrialmatrixintotheintermembranespaceofthemitochondria
1Glucose=36ATPwith2ATPproducedfromglycolysisisbeingusedagainto
producedNADH2inglycolysis)