LIPIDS AND BIOLOGICAL MEMBRANES · Lipids are all water insoluble biomolecules aside from carbohydrates, proteins and nucleic acids. 2 Fay acid based

LIPIDSANDBIOLOGICALMEMBRANESHLeeYuJsuicoJunsay

DepartmentofChemistry

SchoolofScienceandEngineering

AteneodeManilaUniversity1

Lipidsareallwaterinsolublebiomoleculesasidefromcarbohydrates,proteinsandnucleicacids.

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FaGyacidbased Non‐faGyacidbased

FATTYACIDBASEDLIPIDS

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Fa8yacidsarecarboxylicacidswithlong,unbranchedaliphaLcchain.

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SaturatedFa8yacids–Nodoublebonds


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UnaturatedFa8yacids–presenceofdoublebonds.

Monounsaturated–betweenC9andC10.


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HO

O

Linolenicacid

9 10 12 13 15 16 ω

ThecarbonchaindictatesphysicalandchemicalproperLesoffaGyacids

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Fa8yAcid Condensed Solubility(g/LsoluHon) MP

Caprylic C8:0 0.7 16.7

Capric C10:0 0.15 31.6

Lauric C12:0 0.055 44.2

MyrisLc C14:0 0.02 53.9

PalmiLc C16:0 0.007 63.1

Stearic C18:0 0.003 69.6

Oleic C18:1(cis) 16.2

Elaidic C18:1(trans) 43.7

Linoleic C18:2 ‐5

hGp://www.cyberlipid.org/cyberlip/home0001.htm


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COOH: CanreactwithbasestoformSOAPS

-O

O

Na+

Polarhead Non‐polartail

AggregaLontoformmicelles

Iodinevaluetest


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HO

O

Linolenicacid

Alkenes: CanreactviaelectrophilicaddiLon CanreactviaoxidaLon/reducLonreacLons

SuscepLbletoAUTOOXIDATIONwhenexposedtoair!OXIDATIVERANCIDITY

O

O

FaGyacidsmaybereactedwithAlcoholstoformesters.

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Beeswax Carnauba Leafwax

WAXES:ESTERSofFATTYACIDSandLONGALCOHOLS

AcylglycerolsareestersoffaGyacidwithglycerol.

1‐Monoglyceride2‐Monoglyceride1,2‐Diglyceride1,3‐DiglycerideTriglyceride

=FATS

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13

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Triglyceridescanbedegradedinthepresenceofwater:HYDROLYTICRANCIDITY.

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AddiLonofBasescanalsocleavetheesterlinkagetoformglycerolandsoaps:SAPONIFICATION.

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Doublebondsmaybehydrogenatedtoformsaturatedfats(butthisisusuallyincomplete)resultsintotransfats.

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Doublebondsmaybehydrogenatedtoformsaturatedfats(butthisisusuallyincomplete)resultsintotransfats.

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Lipidscanhavechargedorpolarparts,creaLngamphiphilicmolecules.

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Phospholipidsarelipidsthatcontainaphosphategroup

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Phospholipidsdifferontheirpolargroups

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Phospholipidsdifferontheirpolargroups

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Sphingolipidsarelipidsthathavethesphingosinebackbone

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Becauseoftheirshape,phospholipidsformbilayersinsteadofmicelles

NON‐FATTYACIDBASEDLIPIDS:ISOPRENOIDS

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Isoprenoidsmakeupanotherclassoflipids.Theyarecomposedofisopreneunits.

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Isoprenoidsaregroupedaccordingtohowmanyisopreneunitsmakeupthecompound

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No.ofIsopreneunits Name

1(C5) Hemiterpenes

2(C10) Monoterpenes

3(C15) Sesquiterpenes

4(C20) Diterpenes

6(C30) Triterpenes

SterolsandSteroidsarederivedfromTriterpenes.Amongthemostfamousoftheseischolesterol.

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Whilecholesterolisanintegralpartofthecellmembrane,italsoservesasaprecursortohormonesandbileacids.

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Plantsalsohavesimilarsterolmoleculescalledphytosterols.

Theyaresaidtolowercholesterollevelsinblood.

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EICOSANOIDSANDOTHERLIPIDS

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Eicosanoidsarederivedfromarachidonicacidandhavehormone‐likeacLvity

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COX‐1:consLtuLveCOX‐2:inflammatoryresponse

UseofNSAIDs


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Pheromonesaresignalingsubstancesthatarereleasedbyoneorganismtoalterthebehaviorofanotherorganism

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ElectroncarriersareimportantmoleculesforenergyharvesLngfromelectrons(intheelectrontransportchainandphotosynthesis)

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ElectroncarriersareimportantmoleculesforenergyharvesLngfromelectrons(intheelectrontransportchainandphotosynthesis)

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FATSANDHEALTH

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FuncLonsofFats•  Usedtobuildcellsandpartsofthecell(e.g.braincells,nerve

Lssues,cellmembrane)

•  StoredinthebodyinadiposeLssue–  AdiposeLssuearecalledfatdepots

•  Surroundvitalorgans(e.g.heart,kidney,spleen)toserveasprotecLvecushion

•  StoredundertheskinforinsulaLon•  FatreservesareconvertedtoglycerolandfaGyacids(9kcal

pergram)–  Glycerolisburnedforenergyorconvertedtoglucose

Thehumanadipocyte

•  ComposeadiposeLssue•  Forstorageandsynthesisof

triacylglycerides,insulaLon,energystorage(higherenergycontentthanglycogen)

•  Whitefatcells:lipiddropletwithperipheralcytoplasmandnucleus;semi‐liquidfatwithsomesterolderivaLves

•  Brownfatcells:lipiddropletsscaGered,highmitochondriacontent

www.cnrs.fr,www.vulgaris‐medical.com

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FatsTransport•  Someimportantbloodlipoproteins–  Groupofproteinswithatriglycerideorcholesterol

–  Very‐lowdensitylipoprotein(VLDL)•  TransportnewtriglyceridesfromlivertoadiposeLssue

–  Lowdensitylipoprotein(LDL)•  Transportcholesterolfromlivertocells

–  Highdensitylipoprotein(HDL)•  TransportcholesterolfromLssuestoliver

Atherosclerosis:Notjustasimplecloggingproblem!

From:hGp://www.nia.nih.gov/NR/rdonlyres/C3B176CB‐3173‐4F89‐8FDA‐2774FB751108/4227/pic_atherosclerosis.jpg

Cholesterolbiosynthesis

From:hGp://banon.cshl.edu/cgi‐bin/eventbrowser?DB=gk_current&FOCUS_SPECIES=Homo%20sapiens&ID=191273&

Loweringcholesterolsynthesis

•  Usehypolipidemicdrugs(eg.StaLns)•  STATINSareHMG‐CoAinhibitors– Eg.LovastaLn

Tablefrom:hGp://en.wikipedia.org/wiki/StaLn

CriscoandOlestra(byP&G)

1911:Shortening

“Toeat,ornottoeat‐fatistheques1on.”‐fromtheIntroduc1onofMaryEnig,KnowyourFats:TheCompletePrimerforUnderstandingtheNutri1onofFats,Oils,andCholesterol,BethesdaPress,USA,2000.

Olestra•  1998,ProctorandGambleintroducedanewfat/oilsubsLtutecalledOlestra(brandnameOlean®

•  materialreplacesfatsinsnackfoodssuchaspotatochips

•  claimedthatfoodusingOlestrainplaceofdigesHblefatsprovidelesscaloriessincetheOlestraisnotdigestedandpassesthroughthebodyunchanged

•  Somesideeffectsincludeabdominalcrampingandloosestools

Olestra

HowdoesOlestrawork?

hGp://www.cnn.com/HEALTH/9802/10/fakefat.olestra/olestra.large.jpg

Olean®

Olean®

hGp://staLc.howstuffworks.com/gif/quesLon526‐fat‐chips.jpghGp://staLc.howstuffworks.com/gif/quesLon526‐olestra‐chips.jpg

CarniLneCraze

•  ResponsibleforfaGyacidtransportfromcyosoltomitochondriawheretheFAismetabolised

•  NaturallysynthesizedfromLysandMet(L‐isomer)inliverandkidneys

ImagefromhGp://en.wikipedia.org/wiki/Image:Acyl‐CoA_from_cytosol_to_the_mitochondrial_matrix.gif

CarniLneCraze•  Highestamountinmeat,dairy,nuts•  Healthyindividuals,includingstrict

vegetarians,generallysynthesizeenoughL‐carniLnetopreventdeficiency.

•  TherolesofL‐carniLnesupplementaLonasanadjuncttostandardmedicaltherapyinmyocardialinfarcLon,heartfailure,anginapectoris,Alzheimer'sdisease,andHIVinfecLonrequirefurtherresearch.

•  Althoughrecentstudiesinratssuggestacetyl‐L‐carniLnesupplementaLonmaybebeneficialinprevenLngage‐relateddeclinesinenergymetabolismandmemory,itisnotknownwhetheracetyl‐L‐carniLnesupplementaLonwillhelppreventsuchage‐relateddeclinesinhumans.

•  ThereisliGleevidencethatL‐carniLnesupplementaLonimprovesathleLcperformanceinhealthypeople.

Infofrom:hGp://en.wikipedia.org/wiki/CarniLne,TheLinusPaulingInsLtute(OregonStateUniversity).hGp://lpi.oregonstate.edu/infocenter/othernuts/carniLne/

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BIOLOGICALMEMBRANES

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Biologicalmembranesservesmanypurposes:

1.  Physicalbarrier2.  SelecLvefilter3.  CommunicaLon4.  Energymanagement

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Biologicalmembranesaresupramolecularassembliesofproteins,lipidsandcarbohydrates.

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Biologicalmembranesaresupramolecularassembliesofproteins,lipidsandcarbohydrates.

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Lipids:PhospholipidsSphingolipidsSterolsGlycolipids

Proteins:IntegralproteinsPeripheralproteinsGlycoproteins

Lipidbilayersmakeupthemainmatrixormembraneenvironment.

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Liposomes:phospholipidbilayers

MembranesaremadeupmostlyofphospholipidswhichcanfreelymoveinalateraldirecLon(FLUID).

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PhospholipidcomposiLonofthemembraneisasymmetrical.

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Otherlipidmoleculesgiverigiditytothemembrane

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MembranelipidsallowfordynamicacLonsofmembranes

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Integralproteins:spansthemembrane(monolayerorbilayer)

Peripheralproteins:noncovalentlybondedtointegralproteins

IntegraLonofproteinsmaybeviaalphahelices,betabarrelsorcovalentlinkagetolipids

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BecauseofthisfluidcombinaLonofdifferentmolecules,thecurrentlyacceptedmodelformembranesistheFluidMosaicModel.

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MEMBRANETRANSPORT

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Membranesregulatetheflowofmoleculesinandoutofthecell

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Studiesusingtheplanarbilayersshowthatmembraneshaveverylowpermeabilitytoionsandmostpolarmolecules

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•  Thepermeabilitycoefficientsofsmallmoleculesarecorrelatedwiththeirsolubilityinanonpolarsolventrela8vetotheirsolubilityinwater(KD)

•  Totraverseamembrane,asmallmolecule

1.shedsitssolvaLonshellofwater

2.becomesdissolvedinthehydrocarboncoreofthemembrane

3.diffusesthroughthecore

4.becomesresolvatedwithwater

MembranesallowpassiveandacLvetransportofmolecules

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Passive:noenergyneededAcHve:needsATP!

MembranesallowpassiveandacLvetransportofmolecules

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Passive:noenergyneededAcHve:needsATP!

Proteinmediatedpassivetransport(alsocalledfacilitateddiffusion)maybeofdifferentmodes

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Aquaporinsfacilitatediffusionofwateracrossthemembrane

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AcLvetransportneedsenergy.UsuallyittransportsmoleculesfromregionsoflowconcentraLontoregionsofhighconcentraLon.

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ProtonpumpsinthemitochondriaaredrivenbyhighenergyelectronswhileATPsynthaseisapassivetransportsystemthatcounteractsanimbalanceof+chargeononesideofthemembrane.

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LIPIDS AND BIOLOGICAL MEMBRANES · Lipids are all water insoluble biomolecules aside from carbohydrates, proteins and nucleic acids. 2 Fay acid based