Lipids -composition

Lipids composition- Glycerol and fatty acids. Classification of fatty acids

1. LIPIDS
(COMPONENTS)
FORTH SEM BIOCHEMISTRY

2. LIPIDS
The term ‘Lipids’ first coined by German Biochemist Bloor in 1943
Lipids are important heterogenousgroup of organic substances in plant and
animal tissue
Chief concentrated storage form of energy
These are related either actually or potentially to the fatty acids
Chemically these are esters of alcohol (commonly glycerol)with fatty acids
Insoluble in water and soluble in nonpolarorganic solvents like ether,
chloroform, acetone, benzene etc( fat solvents)
Hydrophobic in nature
Oily or greasy substances
Unlike carbohydrates and proteins these are not polymers
Lipids are mostly small molecules
In addition to alcohol and fatty acids, some of the lipids may contain
phosphoric acid, nitrogenous base and carbohydrates.
“Lipids may be regarded as organic substances relatively insoluble in water, soluble in organic
solvents actually or potentially related to fatty acids and utilized by the living cells.”

3. Functions of lipids
Storageformofenergy(triglycerides)
Structuralcomponentsofbiomembranes(phospholipidsandcholesterol)
Metabolicregulators(steroidhormonesandprostaglandins)
Actassurfactants,detergentsandemulsifyingagents(amphipathiclipids)
Actaselectricinsulatorsinneurons
Provideinsulationagainstchangesinexternaltemperature(subcutaneous
fat)
Giveshapeandcontourtothebody
Protectinternalorgansbyprovidingacushioningeffect(padsoffat)
Helpinabsorptionoffatsolublevitamins(A,D,EandK)
Improvetasteandpalatabilityoffood.

4. Composition of lipids
1. ALCOHOL
The alcohol found in lipids are saturated
It include glycerol and higher alcohol such as cetylalcohol, myricyl
alcohol etc
The unsaturated alcohol present in lipids are pigments like phytol
(constituent of chlorophyll), lycophyll(pigment in tomato)
Glycerol is the most common alcohol present in lipids
Glycerol is a 3C compound. The 1
st
and 3
rd
C atom are identical
Glycerol
Cetylalcohol
CH
3
-(CH
2
)
14
-CH
2
OH
Myricylalcohol
CH
3
-(CH
2
)
28
-CH
2
OH

5. Composition of lipids
2. FATTY ACID
Fattyacids(FA)arethecarboxylicacidswithhydrocarbonsidechain
Generalformula,R—CO—OH,whereCOOH(carboxylicgroup)represents
thefunctionalgroup
DependingontheRgroup(thehydrocarbonchain),thephysicalpropertiesof
fattyacidsmayvary
Thesearelongchainorganicacidshavingusually4-30carbonatoms
Itcontainsonlyonecarboxylicgroup(monocarboxylic)
Thenonpolarhydrocarbontailmakesthelipidshydrophobicinnatureand
oilyorgreasy
Containsevennumberofcarbonatomsasthesearesynthesizedfrom2C
units.
Theseareusuallystraightchainderivatives.Stillotherpossessringstructure
(cyclicFA)
Somecontainshydroxylgroups(hydroxyoroxygenatedfattyacids)
Do not occur in free state in tissues ,found in covalently bound form
If free, the carboxyl group of fatty acid will be ionized

6. Fatty acids

7. Nomenclature of fatty acid
Thesystemicnameisbasedonthehydrocarbonfromwhichisderived
(Genevansystem)
Thesaturatedfattyacidendwithasuffix–anoic(eg:octanoicacid)whilethe
unsatuatedfattyacidendwithsuffix–enoic(eg:octadecenoicacid)
ThepositionofCatominthefattyacidchainisindicatedeitherbynumbering
(1,2,3etc)orbyuseofGreekletters(α,βetc)
Thenumberingstartsfromthecarboxylcarbon(fromthe–COOHcarbon)–
carbonNo.1.(C1)
Thecarbonadjacentto–COOHgroup-carbonnumber2(α-carbon),then
carbonatom3(β-carbon)andsoon.
Theend–CH3carbonisknownastheω-carbon(‘Omega’carbon).
starting from the methyl end, the carbon atoms may be numbered as omega
(ω)-1,2,3, etc.
6 5 4 3 2 1
CH3 —CH2 —CH2 —CH2—CH2 —COOH
ω1 ω2 ω3 ω4 ω5
6 5 4 3 2 1
CH3 —CH2 —CH2 —CH2—CH2 —COOH
ω δ γ β α

8. Nomenclature of fatty acid (conts…)
Widelyusedconventiontoindicatethenumberandpositionofthedoublebond(s)in
thecaseofunsaturatedfattyacidsistowritethenumberofcarbonatoms,thenumber
ofdoublebond(s)andthepositionofthedoublebonds(s)belowthenameoftheacid.
Forexample,
1.Oleicacidhaving18carbonatomsandadoublebondbetweencarbonatoms9and10
iswrittenas18:1;9.
2.Linoleicacid(18carbonatomsand2doublebondsatC9andC12)iswrittenas18:2;
9,12.
Analternativemethodtowritethenameofanunsaturatedfattyacidistowritefirst
thepositionofdoublebond(s)innumeralsandthenthetotalnumberofcarbonatoms
inRomanfollowedbythesuffix-enoicacid.
Eg:
1.Oleicacidwrittenas9-octadecenoicacidand
2.Linoleicacidwrittenas9,12-octadecadienoicacid.
Otherrepresentations
∆representsdoublebonds-eg:∆9indicatesdoublebondisbetween9and10
ω–eg:ω6seriesindicatesdoublebondisbetween6and7fromtheωend.

9. Classification of fatty acids
1.Based on the presence or absence of double bond
•Saturated FA (no =bond)
•Unsaturated FA (1 or more =bond)
2. Based on nature of chain
•Straight chain FA
•Branched chain FA
•Cyclic fatty acids
•Hydroxyor oxygenated fatty acids
3. Based on total number of carbon atoms
•Even chain FA
•Odd chain FA
4. Based non length of hydrocarbon chain
•Short chain FA (2 to 6 carbon atoms)
•Medium chain FA (8 to 14 carbon atoms)
•Long chain FA (16 to 22 carbon atoms)
•Very long chain FA (>24 carbon atoms)

10. 1.Based on the presence or absence of double bond
1. SATURATED FATTY ACIDS
>Containsonlysinglebonds
>ThegeneralformulafortheseacidsisC
nH
2n+1COOH.
>Eg:butanoicacid(C4)-C
3H
7COOH orCH
3-CH
2-COOH or
CH
3-(CH
2)
2-COOH
>Saturatedfattyacidsmayfoundin
a.Straightchainfattyacids
#Evennumbered-eg:palmiticacid(16C),stearicacid(18C)
#Oddnumbered-eg:propionicacid(3C),Valericacid(5C)
b.Branchedchainfattyacids
#Evennumbered–eg:Isopalmiticacid(16C)
#Oddnumbered-eg:Anteisopalmiticacid(17C),
Tuberculostearicacid(19C)

11. STRAIGHT CHAIN -EVEN NUMBERED FATTY ACIDS
Trivial name Systemic name Carbon
skeleton
structure Common source
Aceticacid Ethanoicacid 2 : 0 CH
3COOH Vinegar
Butyricacid n-Butanoicacid 4 : 0 CH
3 (CH
2)
2COOH Butter
Caproicacid n-Hexanoicacid 6 : 0 CH
3 (CH
2)
4COOH Butter,Coconutoiland
palmoils
Caprylicacid n-Octanoicacid 8 : 0 CH
3 (CH
2)
6COOH Coconutoiland
palmoils
Capricacid n-Decanoicacid 10 : 0 CH
3 (CH
2)
8COOH Coconutoiland
palmoils
Lauricacid(laurus=laurel
plant)
n-Dodecanoicacid 12 : 0 CH
3 (CH
2)
10COOH Laureloil,
Spermaceti
Myristicacid
(Myristica=nutmeg)
n-Tetradecanoicacid 14 : 0 CH
3 (CH
2)
12COOH Butterandwool
Fats
Palmiticacid
(palma=palmtree)
n-Hexadecanoicacid 16 : 0 CH
3 (CH
2)
14COOH Bodyfat
Stearicacid
(stear=hardfat)
n-Octadecanoicacid 18 : 0 CH
3 (CH
2)
16COOH Bodyfat
Arachidicacid
(Arachis=legume)
n-Eicosanoicacid 20 : 0 CH
3 (CH
2)
18COOH Peanutoil(Arachisoil)
Behenicacid n-Docosanoicacid 22 : 0 CH
3 (CH
2)
20COOH Groundnutoil
Lignocericacid
(lignum=wood;cera=wax)
n-Tetracosanoicacid 24 : 0 CH
3 (CH
2)
22COOH Groundnutoiland
Rapeseedoils
Ceroticacid n-Hexacosanoic 26 : 0 CH
3 (CH
2)
24COOH Woolfat
Montanicacid n-Octacosanoic 28 : 0 CH
3 (CH
2)
26COOH

12. STRAIGHT CHAIN -ODD NUMBERED FATTY ACIDS
Trivial name Systemic name Carbon
skeleton
structure Common
source
Prpionicacid n-Propanoicacid 3 : 0 CH
3CH
2COOH Metabolic
intermediate
Valericacid n-Pentanoicacid 5 :0 CH
3(CH
2)
3COOH Metabolic
intermediate
BRANCHED CHAIN -EVEN NUMBERED FATTY ACIDS
Isopalmiticacidn-Isohexadecanoic
acid
16 : 0 Woolfat
BRANCHED CHAIN -ODD NUMBERED FATTY ACIDS
Anteisopalmitic
acid
n-Methyl
hexadecanoicacid
17 : 0 Woolfat
Tuberculostearic
acid
n-Methyl
octadecanoicacid
19 :0 Bacteria

13. 1.Based on the presence or absence of double bond
2. UNSATURATED FATTY ACIDS
>Containsoneoremoredoublebonds
>These may be classified, based on the degree of unsaturation.
A. Monoethenoidacids —Contains one double bond
C
nH
2n–1COOH;
eg: oleic acid.
B. Diethenoidacids —Contain Two double bonds;
C
nH
2n−3COOH;
eg: Linoleicacid.
C. Triethenoidacids —ContainThreedouble bonds;
C
nH
2n−5COOH;
eg:Linolenicacid.
D. Tetraethenoidacids —Contain Four double bonds;
C
nH
2n−7COOH;
eg: Arachidonicacid
>Monoethenoidacids are commonly called as monounsaturated fatty acids (MUFAs)
and the remaining ones aspolyunsaturated fatty acids (PUFAs).

14. ISOMERISM
1.Exhibit geometric isomerism;
Iftheatomsoracylgroupsonsamesideofdoublebond-cisconfiguration
Ifthegroupsonoppositesideofdoublebond-transconfiguration.
➢cis-isomersarelessstablethantrans-isomers.
➢Mostofnaturallyoccurringunsaturatedfattyacidsexistascisisomer
➢Eg:
2.PositionalIsomers:Avariationinthelocationofthedoublebondsalongthe
unsaturatedfattyacidschainproducesisomerofthatcompound.Thus,oleic
acidcouldhave15differentpositionalisomers.

15. ➢DOCOSAHEXAENOICACID:DHA(Ω3,22:6)
➢Docosahexaenoicacid(DHA)isapolyunsaturated
fattyacidwhichissynthesizedfromα-linolenicor
obtaineddirectlyfromdietaryfishoil.Thisfattyacidis
presentinhighconcentrationsinretina,cerebralcortex,
andsperms.
➢DHAisparticularlyneededfordevelopmentofthe
brainandretinaandissuppliedviatheplacentaand
milk.InEFAdeficiency,nonessentialpolyenoicacidsof
theω9familyreplacetheessentialfattyacidsin
phospholipids(PL),othercomplexlipidsand
membranes.

16. OLEIC ACID
18 : 1 ; 9 (ω9 Fatty acid)
C
17H
33COOH
18
CH
3-
17
CH
2-
16
CH
2-
15
CH
2-
14
CH
2-
13
CH
2-
12
CH
2-
11
CH
2-
10
CH=
9
CH-
8
CH
2-
7
CH
2-
6
CH
2-
5
CH
2-
4
CH
2-
3
CH
2-
1
COOH-
2
CH
2
LINOLEIC ACID
18 : 2 ; 9, 12 ,(ω6 Fatty acid)
C
17H
31COOH
18
CH
3-
17
CH
2-
16
CH
2-
15
CH
2-
14
CH
2-
13
CH=
12
CH-
11
CH
2-
10
CH=
9
CH-
8
CH
2-
7
CH
2-
6
CH
2-
5
CH
2-
4
CH
2-
3
CH
2-
2
CH
2-
1
COOH-
ARACHIDONIC ACID
20 : 4 ; 5, 8, 11, 14(ω6 Fatty acid)
C
19H
31COOH
20
CH
3-
19
CH
2-
18
CH
2-
17
CH
2-
16
CH
2-
15
CH=
14
CH-
13
CH
2-
12
CH=
11
CH-
10
CH
2-
9
CH=
8
CH-
7
CH
2-
6
CH=
5
CH-
4
CH
2-
1
COOH-
2
CH
2-
3
CH
2
LINOLENIC ACID
18 : 3 ; 9, 12, 15 (ω3 Fatty acid)
C
17H
29COOH
18
CH
3-
17
CH
2-
16
CH=
15
CH-
14
CH
2-
13
CH=
12
CH-
11
CH
2-
10
CH=
9
CH-
8
CH
2-
7
CH
2-
6
CH
2-
5
CH
2-
4
CH
2-
3
CH
2-
1
COOH-
2
CH
2

17. MONO UNSATURATED FATTY ACIDS
TRIVIAL NAME SYSTEMIC NAME C SKELETON STRUCTURE COMMON SOURCE
Crotonicacid 2-butenoic acid 4 : 1 ; 2 CH
3CH=CHCOOH Croton oil
Myristoleicacid 9-tetradecenoic acid14 : 1 ; 9 CH
3(CH
2)
3CH=CH(CH
2)
7COOH Pycnanthyus
Palmitoleicacid 9-hexadecenoic acid16 : 1 ; 9 CH
3(CH
2)
5CH=CH(CH
2)
7COOH Animal and plant
fats
Oleic acid
(oleum= oil)
9-octadecenoic acid18 : 1 ; 9 CH
3(CH
2)
7CH=CH(CH
2)
7COOH Animal and plant
fats
Vaccenicacid 11-octadecenoic acid18 : 1 : 11 CH
3(CH
2)
5CH=CH(CH
2)
9COOH Bacterial fat
POLY UNSATURATED FATTY ACIDS
Linoleicacid
(linon= flax)
9, 12-octadecadienoic
acid
18 : 2 ; 9, 12 CH
3(CH
2)
4CH=CHCH
2CH=CH
(CH
2)
7COOH
Linseed and cotton
seed oils
Eleostearicacid 9, 11, 13-
octadecatrienoic acid
18 : 3 ; 9, 11,
13
CH
3(CH
2)
3CH=CH-CH=CH-
CH=CH(CH
2)
7COOH
Tung oil
Linolenicacid 9, 12, 15-
octadecatrienoic acid
18 : 3 ; 9, 12,
15
CH
3CH
2CH=CHCH
2CH=CHCH
2CH=CH(C
H
2)
7COOH
Linseed oil
Arachidonicacid 5, 8, 11, 14-
eicosatetraenoic acid
20 : 4 ; 5, 8,
11, 14
CH
3(CH
2)
4CH=CHCH
2CH=CHCH
2
CH=CHCH
2CH=CH(CH
2)
3 COOH
Animal fat

18. Unusual unsaturated fatty acid
Nemotinicacid(16C)
Itisexcretedinthegrowthmediumbyacitrivorium
mould.
Thisfattyacidisuniqueinthatitcontainsthesingle,
doubleandtripleC—Clinkages.
Nemotinicacidisoneofthefewnaturally-occurring
compoundscontainingtheallenegroup

19. 2. Based on nature of chain
1.STRAIGHT CHAIN FATTY ACIDS
Linearchain
Eg:
1.Palmiticacid(C16)
16
CH
3-
15
CH
2-
14
CH
2-
13
CH
2-
12
CH
2-
11
CH
2-
10
CH
2-
9
CH
2-
8
CH
2-
7
CH
2-
1
COOH-
2
CH
2-
3
CH
2-
4
CH
2--
5
CH
2-
6
CH
2
2.Stearicacid(C18)
2.BRANCHED CHAIN FATTY ACIDS
Eg:Anteisopalmiticacid(C17)(Methylhexadecanoicacid)
18
CH3-
17
CH2-
16
CH2
15
CH2-
14
CH2-
13
CH2-
12
CH2-
11
CH2-
10
CH2-
9
CH2-
8
CH2-
7
CH2-
6
CH2-
1
COOH-
2
CH2--
3
CH2-
4
CH2
5
CH2

20. 2. Based on nature of chain
3.HYDROXY OR OXYGENATED FATTY ACIDS
Ricinoleicacid (found in castor oil -87%). It is a C 18 acid with a double bond at C9 and an
OH group on C12.
Cerebronicacid, a C 24 acid obtained from animal lipid, is another important hydroxyacid
with an OH group on C2.
9, 10 dihydroxystearicacid(C18). A common oxygenated fatty acid, isolated from plants and
bacterial lipids.
9, 10-epoxystearic acid (C18)is isolated from rust spore lipids (20%).

21. 4. CYCLIC FATTY ACIDS
Theseareofrareoccurrence.
HydnocarpicacidandChaulmoogricacid.Chaulmoograoil,obtainedfromtheplant
Hydnocarpuskurzilandusedinthetreatmentofleprosy,contains2suchacids.Chaulmoogric
acidhasacyclopentenylringinits18-carbonstructure..
Lactobacillicacid,Lipidsfromthelactobacillicontainafattyacid,withacyclopropylgroup.
Thisfattyacidmayresultfromtheadditionofamethylenegroupacrossthedoublebond
ofvaccenicacid.
Sterculicacidfromplantsourceshasacomparablestructure,withasuggestedrelationship
tooleicacid.Itmaybederivedfromoleicacidbytheadditionofamethylenegroup
acrossthedoublebondinamannerthattheunsaturatednatureisnotaltered,unlikethe
lactobacillicacid.
2. Based on nature of chain

22. 3. Based on total number of carbon atoms
1. EVEN CHAIN FATTY ACIDS
Eg:palmiticacid(16C)
Stearicacid(18C)
Isopalmiticacid(16C)
2. ODD CHAIN FATTY ACIDS
Eg:Valericacid(5C)
Propionicacid(3C)
Tuberculostearicacid(19C)

23. 4. Based non length of hydrocarbon chain
•Short chain FA (2 to 6 carbon atoms)
•Acetic acid(2C), Caproicacid(6C)
•Medium chain FA (8 to 14 carbon atoms)
•Caprylicacid (8C), Myristicacid (14C)
•Long chain FA (16 to 22 carbon atoms)
•Palmiticacid(16C), Behenicacid(22C)
•Very long chain FA (>24 carbon atoms)
•Cerotic acid(26C)

24. ESSENTIAL FATTY ACIDS
The fatty acids that cannot be synthesized by
the body and therefore, should be supplied
through diet is known as essential fatty
acids(EFA)
Chemicallytheyarepolyunsaturatedfattyacids(PUFA)
Eg:linoleicacid(ω6,18C,Δ9,12)
Linolenicacid(ω3,18C,Δ9,12,15)
Arachidonicacid(ω3,20C,Δ5,8,11,14)
NormaldietaryallowanceofPUFAis2-3%oftotal
calories.

25. ESSENTIAL FATTY ACIDS(conts..)

26. ESSENTIAL FATTY ACIDS(conts..)
BIOCHEMICAL BASIS OF ESSENTIALITY
Humanslacktheenzymethatcanintroducedouble
bondsbeyondcarbons9to10
Introductionofadditionaldoublebondsinunsaturated
fattyacidislimitedtotheareabetween–COOH
groupandtheexistingdoublebondandthatitisnot
possibletointroduceadoublebondbetweenthe–
CH3groupattheoppositeendofthemoleculeandthe
firstunsaturatedlinkage.Thiswouldexplainbody’s
inabilitytosynthesiseanEFAfromoleicacid.

27. ESSENTIAL FATTY ACIDS(conts..)
Functions of EFA
Structuralelementsoftissues:Polyunsaturatedfattyacidsoccurinhigherconcentrationinlipidsassociated
withstructuralelementsoftissues.
Structuralelementofgonads:Lipidsofgonadsalsocontainahighconcentrationofpolyunsaturatedfatty
acids,whichsuggestsimportanceofthesecompoundsinreproductivefunction.
Synthesisofprostaglandinsandothercompounds:ProstaglandinsaresynthesisedfromArachidonicacid
bycyclooxygenaseenzymesystem.Leucotrienesareconjugatedtrienesformedfromarachidonicacidin
leucocytesbytheLipoxygenasepathway.
Structuralelementofmitochondrialmembrane:AdeficiencyofEFAcausesswellingofmitochondrial
membraneandreductioninefficiencyofoxidativephosphorylation.Thismayexplainforincreasedheat
productionnotedinEFAdeficientanimals.
Serumlevelofcholesterol:Fatswithhighcontentofpolyunsaturatedfattyacidstendstolowerserumlevel
ofcholesterol.
Effectonclottingtime:ProlongationofclottingtimeisnotediningestionoffatsrichinEFA.
Effectonfibrinolyticactivity:AnincreaseinfibrinolyticactivityfollowstheingestionoffatsrichinEFA.
RoleofEFAinfattyliver:DeficiencyofEFAproducesfattyliver.
Roleinvision:Docosahexaenoicacidisthemostabundantpolyenoicfattyacidspresentinretinal
photoreceptormembranes.Docosahexaenoicacidisformedfromdietarylinolenicacid.Itenhancesthe
electricalresponseofthephotoreceptorstoillumination.Hencelinolenicacidisnecessaryinthedietfor
optimalvision.

28. ESSENTIAL FATTY ACIDS(conts..)
DEFICIENCY MANIFESTATIONS:
A deficiency of EFA has notyetbeen unequivocally demonstrated in humans.
In weaning animals, symptoms of EFA deficiency are readily produced. They are:
Cessation of growth.
Skin lesions: Acanthosis(hypertrophy of prickle cells) and hyperkeratosis
(hypertrophy of stratum corneum). Skin becomes abnormally permeable to water.
Increased loss of water increases BMR.
Abnormalities of pregnancy and lactation in adult females.
Fatty liver accompanied by increased rates of fatty acids synthesis, lessened
resistance to stress.
Kidney damage.
FATE OF EFA
EFAundergoesβ-oxidationafternecessaryisomerisationand
epimerisation,likeotherunsaturatedfattyacids

29. REFERENCE
Dr. M.N. Chatterjea, and RanaShinde; Extbookof Medical
Biochemistry; Eighth Edition ;JaypeeBrothers Medical
Publishers (P) Ltd
D.M .Vasudevan, SreekumariS., and KannanVaidyanathan;
Textbook of Biochemistry, For Medical Students; Sixth
Edition; JaypeeBrothers Medical Publishers (P) Ltd
J.L. Jain, SunjayJain and NitinJain; Fundamentals of
Biochemistry for University and College Students in India
and Abroad; Sixth Edition; S. Chand& Company Ltd.; 2005
Dr. U. Satyanarayanaand U. Chakrapani; Biochemistry;
Fourth Edition; Elsevier India Pvt. Ltd; 2013