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Fattyacidmetabolism–topicsRoleoflipases–breakdownoftriglyceridesandphospholipidsActivationoffattyacidsfortheβ-oxidationcycle(CoASH)Transportintothemitochondria(carnitine)β-oxidationpathwayEvenchainsaturatedFAUnsaturatedFAOddnumberedFARoleofbiotinandVitB12EnergycalculationsStarvationEnergysourcesforexerciseFattyacidoxidation-energyfromlipidsLongchainFAserveasmainsourceforanimals:FAareoxidizedandbrokendowntoAcCoA.Thereleaseofelectrons(NADH)drivesATPsynthesisEnergyTheproductionofAcCoAfeedstheTCAcycleEnergySourcesofFA:DietCellstorage(lipiddroplets)Synthesis(excesscarbs,etc.)FattyacidoxidationoutlineLipasesareproducedinthepancreasRoleofLipasesBreakdownofTriglyceridesTriglyceridesingestedwaterinsolubleEmulsifiedbybilesalts(detergents)inintestineLipasesbreakthemdowntofattyacidsandglycerolwhicharetakenupbyintestinalmucosaTriglyceridesstoredinadiposetissueBrokendownbylipases,triggeredbyhormonalsignals(epinephrine,glucagon)LipasesR=fattyacidchain(CH2)nCH3BreakdownofphospholipidsbyphospholipasesPhospholipasesA(1and2),C,andD.PhospholipasesimportantforintracellularsignalsEx:InositoltriphosphatefromPhosphotidylinositolwhichisinvolvedinsignallingCa+releasefromER(musclecontraction,otheracitivties)Phospholipasesalsopresentinsnakevenomandwasp/beepoisonsβ-oxidationSequentialbreakdownoffattyacidstoyieldAcCoAOccursinmitochondria(likeTCA)Seriesof4basicstepsthatarerepeatedoverandoverAcCoAproducedTCAcycleCO2andenergyForaC16wehave7roundsofβ-oxidationtoyield:8AcCoA7NADH7FADH2β-oxidationPalmiticacid(C16):C15H31COOH+2302

16CO2+16H2O ∆Go`=-9773KJ/molGlucose(CH2O)6+6O2

6CO2+6H2O ∆Go`=-2868KJ/molPalmiticacidhasmanymorecarbonstooxidizeandismuchmorereducedΒ-oxidation-transportintomitochondriaThefattyacids,oncetakenupbythecell,mustbetransportedtothemitochondriaFattyAcylCoASynthetaseisboundtomitochondrialoutermembraneSummaryoftransportActivationwithCoASHbyfattyacylCoAsynthetaseTransportacrossmitochondrialINNERmembranebylinkingwithcarnitinebycarnitineacyltransferaseIandremovalbycarnitineacyltransferaseII.Fattyacylesterlinkagehereβ-oxidationofstraightchainFAAcylCoAdehase:Has3isoenzymes:Longchain(12-18C)Mediumchain(4-14C)Shortchain(4-8C)Thisisrepeated6moretimestoyield:7AcCoA7NADH7FADH27roundsforaC16Whynot8?Β-ketoacyl-CoAthiolaseβ-oxidationofstraightchainFAEnergyyield:Activation:-2ATPΒ-oxidation:

7NADH 17.5ATP7FADH2 10.5ATP8AcCoA:24NADH 60ATP8FADH2 12ATP8GTP 8ATPTotal 106ATPOxidationofpalmiticacid:~9800KJ/mol106ATP:energyfromphosphatebonds:106x30.5KJ/mol=3230KJ/molThereforeefficiencyis3230/9800x100%=33%Comparabletoefficiencyinglycolysisβ-oxidationofstraightchainFAQuestion:HowmuchmoreATPfromstearicacid?(C18)1moreroundβ-oxidation:1NADH,1FADH21moreAcCoA:3NADH,1FADH2,1GTPTotal=14extraATPβ-oxidationofunsaturatedFAMonounsaturatedFAβ-oxidationofunsaturatedFAPolyunsaturatedFA:Ex:linoleicacid(cis-∆9,cis-∆12)Requiresadienoyl-CoAreductase(NADPH)stepaswellasanenoylCoAisomerasestepbeforecontinuingnormalβ-oxidationβ-oxidationofodd-numberedfattyacidsNormalβ-oxidationproceedsuntilweareleftwithaC3chainEx:C17willproceedfor7roundsofβ-oxidation…..CO2incorporatedviaBiotinRoleofbiotin…Biotiniscommonlyusediscarboxylationreactionsascofactor:ATPADPBiotinCarboxybiotinPropionylCoAcarboxylaseMethylMalonylCoAPropionylCoACO2Starvation–fateoffattyacidsWhathappenswhenyou’restarving?Runoutofglucose,glycogenstores(diabetics)BodyinitiatesgluconeogenesisGlucoseneededforkeyareas(brain,etc)TCAcycleintermediates(suchasOAA)aredepletedtodothisβ-oxidationinitiated……AcCoAproducedinlargeamountsPotentialproblem?Starvation–fateoffattyacidsExcessAcCoAproducedthatbodycannotmetabolizeLiverconvertsittoacetoacetateandβ-hydroxybutyrateandreleasesitintobloodAcetoacetateusedbyperipheraltissuesforenergyCanleadtoadecreaseinbloodpH–acidosis(commontodiabetics)EnergysourcesforexerciseCreatine:anotherenergycarrierotherthanATPActsasareservoirofphosphorylgroupsWhenATPisdepletedbyrapidexerciseorexertion,creatine-phosphateisusedtoreplenishATPstoresbythereversereactionCreatineisfoundinmanytissues(muscle,heart,brain)andisfoundat~10xtheconcentrationofATPCreatineissynthesizedinliver(orfromexogenoussources:fishandmeat)mostlystoredinmuscle(

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