BIOSC 1000 Lecture 18: Lecture 18

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plumwhale361

12 Apr 2019

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Lecture18(3/21)

Thursday,March21,2019 10:58AM

LipidCatabolism



•Lipids

○Builtfromfattyacidsortheirderivatives

○Threemaintypes

•Triacylglycerols

•Energystorageformoffattyacids

•Membranelipids

•Phospholipids&sphingolipids

•Cholesterol

•Membranecomponentsandprecursorsofsteroidhormones

•FattyAcidNomenclatureReview

○AcylGroup

•

•Basicallyacarboxylicacidwithoutthe‑OH

○KetoGroup

•



○

•Omegacarbonistheendcarbon

•Triacylglycerolscontain3fattyacidsesterifiedtoglycerol.

○

○CalledfatsorTAGs

○Functioninenergystorage

○Contain3fattyacidsesterifiedtoaglycerol

•EnergyStorageMolecules

○Glycogenvs.Fat

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•

•Takeslotsofvolumetostoreglycogen

•Triacylglycerolsarederivedfromthediet,biosynthesisinliver,andadipocytes.

○

○Primaryformofenergystorageinanimals

○Dietarytriacylglycerolsaretransportedbychylomicrons

•Largelipoproteincomplexes

○TriacylglycerolssynthesizedintheliveraretransportedbyVLDLparticles.

○Triacylglycerolsstoredinadipocytesarereleasedasfreefattyacidsin

responsetohormonesignaling

•Transportedbythecarrierproteinalbumin.

•Dietarytriacyclglycerolsaremetabolizedintheintestineandtransportedtothe

circulatorysystem.

○

○Solubilizedsothatsolublelipasescaninteract

•Bileacids(salts)emulsifydietaryfatsinthesmallintestine,forming

mixedmicelles

•Intestinallipaseshydrolyzetriacylglycerolstogeneratefreefattyacids

•Fattyacidsaretakenupbytheintestinalmucosa(epithelialcells)and

convertedbacktotriacylglycerols

•Triacylglycerolsareincorporatedwithcholesterolandapolipoproteins

intochylomicrons

•Chylomicronsmovethroughthelymphaticsystemandenterthe

bloodstreamtotravel

○PancreaticlipasesconverttriacyglycerolsintoFAandmonoacylglycerolfor

absorptioninintestines.

•Chylomicronstransporttriacylglycerolsanddietarycholesterolthroughthe

lymphaticsystemandbloodstreamtotissues.

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○

○Mainconstituent:triglycerides

•Alsocontaincholesterolesters

○Surroundedbymonolayerofphospholipids

•Phospholipidmembraneisderivedfromtheendomembranesystemof

intestinalepithelialcells

•Embeddedwith~6differentapolipoproteins.

•Apolipoproteinsactassignalsforuptakeandmetabolismof

chylomicroncontents

•Apolipoproteinsonchylomicronsserveassignalsforlipoproteindeliveryand

metabolism.

○

○Lipase

•Enzymethatcleaveslipids

○ApolipoproteinC‑IIbindstolipaseonendothelialcells

•Leadstoreleaseoffattyacidsintothecells

○Fattyacidsenternearbyadipocytesormusclecells

•Ortransportedbyserumalbumin(transport)proteintoothertissues

○Glycerolproducedbylipasereturnstotheliverwhereitisconvertedto

DHAP

•TypesofLipoproteins

○

•VLDL

•Verylowdensitylipids

•Highconcentrationoffat

•TriacylglycerolssynthesizedintheliverarepackagedandtransportedinVLDL

particles.

○

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