Biochemistry Lipids 1 - uomustansiriyah.edu.iq · Biochemistry Lipids 1 2ndyear Biology ......
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BiochemistryLipids1
2nd yearBiologyMustansiriyahUniversity
زھراء سالم محسن. عبیرحازم مصطفى د.د
1
Copyright ©
2007 by Pearson Education, Inc. Publishing as Benjam
in Cum
mings
Lipids
Lipids are are non-polar (hydrophobic) compounds, soluble in organic solvents.
• Most membrane lipids are amphipathic, having a non-polar end and a polar end.
• Biomoleculesthatcontainfattyacidsorasteroidnucleus.
• NamedfortheGreekwordlipos,whichmeans“fat.”
• Extractedfromcellsusingorganicsolvents.2
Lipids are consist of fatty acids (F.As) as a building block and could be grouped as:
1. Neutral fats and oils (triglycerides)3. Phospholipid and sphingolipids 4. Waxes5. Steroids 6. Prostaglandins 6. Fat soluble vitamins
Lipids
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Lipids
Saponificationlipids
TriglycerideOil+fat
Waxes
Phospholipids
SphingolipidsNon-saponification
lipids
Steroids Prostaglandins
Classes of Lipids
LipidsFattyAcids(F.As)
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Fatty acids (F.As) : a hydrocarbon chain with a carboxylic acid at one end.
A 16-C fatty acid:
CH3(CH2)14-COO-
Non-polar polar
OH
O
F.AsFormulas
TheformulasforF.Asarewrittenas• Condensedformulas.• Line-bondformulas.• Forexamplecaprylic acidwith8carbonatoms.CH3—(CH2)6—COOH
CH3—CH2—CH2—CH2—CH2—CH2—CH2—COOH
7OH
O
FattyAcids
F.As• Arelong-chaincarboxylicacids.
• Typicallycontain12-18carbonatoms.
• Arewaterinsoluble.• Canbesaturatedorunsaturated.
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Saturated Fatty Acids
CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OHO
1245678 3
Octanoic Acid
Unsaturated Fatty Acids
CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OHO
1245678 3
CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OHO
1245678 3
3 - Octenoic Acid
3, 6 - Octadienoic Acid
Short hand: 8:1 (D3)
8:2 (D3,6)
Cis 9 - Octadecenoic Acid (oleic)
Trans 9 - Octadecenoic Acid (elaidic acid)
O
CH3(CH2)7 C C (CH2)7 C OHHH
910
OCH3(CH2)7 C C (CH2)7 C OH
H
H
Cis And Trans Fatty Acids
A 16-C fatty acid with one cis double bond between C atoms 9-10 may be represented as 18:1 cis D9.
A 16-C fatty acid with one trans double bond between C atoms 9-10 may be represented as 18:1 trans D9.
Saturated Fatty Acids
Saturatedfattyacids have• SingleC–Cbonds.• Moleculesthatfitcloselytogetherinaregularpattern.
• Strongattractionsbetweenfattyacidchains.
• Highmeltingpointsthatmakethemsolidsatroomtemperature.
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Some Saturated Fatty Acids
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Unsaturated Fatty Acids
Unsaturatedfattyacids• HaveoneormoredoubleC=Cbond.
• Typicallycontaincisdoublebonds.
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PropertiesofUnsaturatedFattyAcids
Unsaturatedfattyacids• Have“kinks”inthefattyacidchains.
• Donotpackclosely.
• Havefewattractionsbetweenchains.
• Havelowmeltingpoints.
• Areliquidsatroomtemperature.
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“kinks” in chain
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Polyunsaturated Fatty Acids
Linoleic acid: Cis, cis, 9, 12 - Octadecadienoic acid
Linolenic acid: Cis, cis, cis 9, 12, 15 - Octadecatrienoic acid
Arachidonic acid: Cis, cis, cis, cis 5, 8, 11, 14 - Eicosatetraenoic acid
Linoleic Acid
Linolenic Acid
Arachidonic Acid
Somefattyacidsandtheircommonnames:14:0 myristic acid;16:0palmitic acid;18:0 stearic acid;18:1cisD9 oleicacid18:2cisD9,12 linoleic acid18:3cisD9,12,15 a-linonenic acid20:4cisD5,8,11,14 arachidonic acid
Double bonds in fatty acids usually have the cis configuration. Most naturally occurring fatty acids have an even number of carbon atoms.
CO
O-12
34a
bg
fatty acid with a cis-D9 double bond
ComparingMeltingPoints of SomeFattyAcids
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Effects of Double Bonds on the Melting Points
16:0 6016:1 118:0 6318:1 1618:2 -518:3 -1120:0 75
Fatty. Acids. Melting point. P. (0C)
20:4 -50
Melting Points of Fatty Acids and Solubility in Water
Solubility in H O
Chain Length
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Melting Point
Mel
ting
poin
t
H2O
LearningCheck
Assignthemeltingpointsof–17°C,13°C,and69°Ctothecorrectfattyacid.Explain.
stearicacid(18C) saturatedoleicacid(18C) onedoublebondlinoleicacid(18C) twodoublebonds
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Solution
Stearicacidissaturatedandwouldhaveahighermeltingpointthantheunsaturatedfattyacids.Becauselinoleichastwodoublebonds,itwouldhavealowermpthanoleicacid,whichhasonedoublebond.
stearicacidmp69°Csaturatedoleicacidmp13°C
linoleicacidmp-17°Cmostunsaturated
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Omega-6andOmega3- FattyAcids
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Fatty acids § In vegetable oils are mostly omega-6 with
the first C=C at C6.linoleic acid CH3─(CH2)4─CH=CH─CH2─CH=CH─(CH2)7─COOH
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§ In fish oils are mostly omega-3 with the first C=C at C3.linolenic acidCH3─CH2─(CH=CH─CH2)3─(CH2)6─COOH
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Publishing as Benjamin Cummings
SomeOmega-6andOmega-3FattyAcids
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LearningCheck
Writeafattyacidwith10carbonatomsthatis:
A.saturated
B.monounsaturatedomega-3
C.monounsaturatedomega-6
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Solution
Writeafattyacidwith10carbonatomsthatis:A.saturatedCH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH2—COOH
B.monounsaturatedomega-3CH3—CH2—CH=CH—CH2—CH2—CH2—CH2—CH2—COOH
C.monounsaturatedomega-6CH3—CH2—CH2—CH2—CH2—CH=CH—CH2—CH2—COOH
26https://youtu.be/Os22YEYObDs
Lipids
FatsandOils
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FatsandOils:Triacylglycerols
Fatsandoils are• Alsocalledtriacylglycerols (TG).• Estersofglycerol.• Producedbyesterification.• FormedwhenOHgroupsofglycerolreactwiththeCOOHofF.AsandliberateH2O
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Fats
Fats are mostly Triglycerides (TG):
Solid
FormationofaTriacylglycerolglycerol+threefattyacidstriacylglycerol
OHCH2
OH
OHCH2
CHO
(CH2)14CH3CHO
O(CH2)14CH3CHO
O(CH2)14CH3CHO
OOC (CH2)14CH3
CH OOC (CH2)14CH3
CH2 OOC (CH2)14CH3
CH2
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+ 3H2O
+
Triacylglycerols
Inatriacylglycerol,• Glycerolformsesterbondswiththreefattyacids.
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GlycerophospholipidsGlycerophospholipids (phosphoglycerides):-commonconstituentsofcellularmembranes.-Theyhaveaglycerol backbone.-HydroxylsatC1 &C2 areesterifiedtofattyacids.
C OHH
CH2OH
CH2OH
glycerol
An ester forms when a hydroxyl reacts with a carboxylic acid, with loss of H2O.
Formation of an ester:
O O
R'OH + HO-C-R" R'-O-C-R'' + H2O
Glycerides
Monoglyceride (a - monostearin) Diglyceride (a, a' - distearin)
H2C OH
HC OH
H2C OOC (CH2)16 CH3
H2C O
HC OH
H2C OOC (CH2)16 CH3
C (CH2)16 CH3
O
Triglyceride (b - palmityl distearin)
H2C O
HC O
H2C OOC (CH2)16 CH3
C (CH2)16 CH3
O
OC (CH2)14 CH3
( C18 )
(C16 )
(C18 )
Oils
Oliveoil• Containsahighpercentageofoleicacid,whichisamonounsaturatedfattyacidwithonecisdoublebond.
(TG+3Oleicacid)Liquid
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Unsaturated fatty acid chains have kinks that do not allow close packing.
LearningCheck
Whatarethefattyacidsinthefollowingtriacylglycerol?
(CH2)12CH3
OC
CH(CH2)7CH3(CH2)7CHOC
O(CH2)16CH3C
O
O
OCH2
CH2
CH
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Solution
(CH2)12CH3
OC
CH(CH2)7CH3(CH2)7CHOC
O(CH2)16CH3C
O
O
OCH2
CH2
CH
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Stearic acid
Oleic acid
Myristic acid
MELTING POINTS OF TRIGLYCERIDES
C6 -15
C12 15
C14 33
C16 45
C18 55
C18:1 (cis) -32
Triglyceride Melting Point (°C)
C18:1 (trans) 15
MeltingPointsofFatsandOils
Atriacylglycerolthatisafat• Issolidatroomtemperature.• Isprevalentinmeats,wholemilk,butter,andcheese.
Atriacylglycerolthatisanoil• Isliquidatroomtemperature.• Isprevalentinplantssuchasoliveandsafflower.
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OilswithUnsaturatedFattyAcids
Oils• Havemoreunsaturatedfats.• Havecisdoublebondsthatcause“kinks”inthefattyacidchains.
• Cannotpacktriacylglycerolmoleculesasclosetogetherasinfats.
• Havelowermeltingpointsthansaturatedfats.• Areliquidsatroomtemperature.
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SaturatedandUnsaturatedFattyAcidsInFatsandOils
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WaxesWaxes are• Estersofsaturatedfattyacidsandlong-chainalcohols.• Coatingsthatpreventlossofwaterbyleavesofplants.
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LipidsPhospholipids
&Glcerophospholipids
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Glycerol
PO4Amino alcohol
Fatty acid
Fatty acid
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PhospholipidsPhospholipids are the major component of all cell membranes.Phospholipid = two hydrophobic F.As "tails" + a hydrophilic"head" which is consisting of a phosphate group.-They can form lipid bilayers because of their amphiphiliccharacteristic.
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Glycerophospholipids (GPL)Glycerophospholipids (GPL)arepolar:• Themostabundantlipidsincellmembranes.• GPL=twochainsoffattyacids+phosphate+anaminoalcohol.
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Glycerol
PO4Amino alcohol
Fatty acid
Fatty acid
StructureandPolarityofAGlycerophospholipid
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GlycerophospholipidsGlycerophospholipids arepolar:
• ThepolaraminoalcoholareethanolamineorcholineandSer
CH3│++
HO−CH2−CH2−N−CH3 HO−CH2−CH2−NH3│
cholineCH3 ethanolamine+NH3│Aminoalcohols
HO−CH2−CH−COO−serine
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O
O
H2C O C RO
R C O CH
H2C O P O CH2 CH2 N+ CH3
CH3
CH3
O_Phosphatidic Acid Choline
Glycerophospholipids
LecithinandCephalin
Lecithin andcephalin areglycerophospholipids• Abundantinbrainandnervetissues.• Foundineggyolk,wheatgerm,andyeast.
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in Cumm
ings
Examplesofglycerophospholipids
LipidsSphingolipids
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SphingolipidsSphingolipids• Aresimilartophospholipids.• Containsphingosine (along-chainaminoalcohol)+afattyacid+phosphate+asmallaminoalcohol.
• Havepolarandnonpolarregions.
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sphingosine
PO4amino alcohol
fatty acid
Sphingosine
Sphingosineisalong-chainunsaturatedaminoalcohol.
CH3−(CH2)12−CH=CH−CH−OH│CH−NH2│CH2−OH
Sphingosine
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Link to F.As
Link to phosphate + amino alcohol
SphingolipidsInsphingomyelin,asphingolipidfoundinnervecells• Thereisanamidebondbetweenafattyacidandsphingosine,an18-carbonalcohol.
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Glycosphingolipids• Glycosphingolipidscontainmonosaccharidesbondedtothe–OHofsphingosinebyaglycosidic bond.
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GlycosphingolipidsandCerebrosidesGlycosphingolipids.• Canbeacerebroside whenlinkedwithgalactose.
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StructuresofLipids
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2007 by Pearson Education, Inc.Publishing as B
enjamin C
umm
ings