Lipids Biomolecules

Lipids A Biomolecules: introduction, chemical nature, classification, and biological role.

1. Lipid
Presented by-Shubhrat Maheshwari
Assistant Professor

2. Definition
•Alipidisatypeoforganicmoleculefoundinlivingthings.Itisoilyorwaxyand
insolubleinwater.Fatsaremadefromlipidmolecules.Lipidsarelongchainsof
carbonandhydrogenmolecules.
•Lipidsareamajorsourceofenergyforthebody,andtheyprovidethehydrophobic
barrier.
•Lipidsserveadditionalfunctionsinthebody,forexample,somefat-solublevitamins
haveregulatoryorcoenzymefunctions,andtheprostaglandinsandsteroidhormoneshaveregulatoryorcoenzymefunctions,andtheprostaglandinsandsteroidhormones
playmajorrolesinthecontrolofthebody'shomeostasis

3. Chemical nature
1.The basic unit of lipids is triglyceride (glycerol and fatty acids).
2. Lipids have hydrophobic hydrocarbon chains.
3. Soluble in organic solvents.

4. General Characters of Lipids
-Lipidsarerelativelyinsolubleinwater.
-Theyaresolubleinnon-polarsolvents,likeether,chloroform,andmethanol.
-Lipidshavehighenergycontentandaremetabolizedtoreleasecalories.
-Lipidsalsoactaselectricalinsulators,theyinsulatenerveaxons.
-Fatscontainsaturatedfattyacids;theyaresolidatroomtemperatures.
Example,animalfats.Example,animalfats.
-Plantfatsareunsaturatedandareliquidatroomtemperatures.
-Purefatsarecolorless,theyhaveextremelyblandtaste.
-Thefatsaresparinglysolubleinwaterandhencearedescribedare
hydrophobicsubstances.
-Theyarefreelysolubleinorganicsolventslikeether,acetoneandbenzene.
-Themeltingpointoffatsdependsonthelengthofthechainoftheconstituent
fattyacidandthedegreeofunsaturation.

5. General characters of Lipids(cont.)
-Geometricisomerism,thepresenceofdoublebondintheunsaturatedfatty
acidofthelipidmoleculeproducesgeometricorcis-transisomerism.
-Fatshaveinsulatingcapacity,theyarebadconductorsofheat.
-Emulsificationistheprocessbywhichalipidmassisconvertedtoanumber
ofsmalllipiddroplets.Theprocessofemulsificationhappensbeforethefats
canbeabsorbedbytheintestinalwalls.canbeabsorbedbytheintestinalwalls.
-Thefatsarehydrolyzedbytheenzymelipasestoyieldfattyacidsand
glycerol.
-Thehydrolysisoffatsbyalkaliiscalledsaponification.Thisreactionresults
intheformationofglycerolandsaltsoffattyacidscalledsoaps.
-Hydrolyticrancidityiscausedbythegrowthofmicroorganismswhich
secreteenzymeslikelipases.Thesesplitfatsintoglycerolandfreefattyacids.

6. Classification of lipids

7. •Classification of lipids
1.Simplelipids:Estersoffattyacidswithvariousalcohols.
a.Fats:Estersoffattyacidswithglycerol.Oilsarefatsintheliquidstate.
b.Waxes:Estersoffattyacidswithhighermolecularweightmonohydricalcohols.
2.Complexlipids:Estersoffattyacidscontaininggroupsinadditiontoanalcoholand
afattyacid.
a.Phospholipids:Lipidscontaining,inadditiontofattyacidsandanalcohol,a
phosphoricacidresidue.Theyfrequentlyhavenitrogencontainingbasesandother
substituents,eg,inglycerophospholipidsthealcoholisglycerolandin
sphingophospholipidsthealcoholissphingosine.sphingophospholipidsthealcoholissphingosine.
b.Glycolipids(glycosphingolipids):Lipidscontainingafattyacid,sphingosine,and
carbohydrate.
c.Othercomplexlipids:Lipidssuchassulfolipidsandaminolipids.Lipoproteinsmay
alsobeplacedinthiscategory.
3.Precursorandderivedlipids:Theseincludefattyacids,glycerol,steroids,other
alcohols,fattyaldehydes,andketonebodies,hydrocarbons,lipid-solublevitaminsand
hormones.

8. Examples of lipid
Fattyacids-Oleicacid,Linoleicacid,Palmitoleicacid,Arachidonic
acid.
-FatsandOils-Animalfats-Butter,Lard,Humanfat,Herringoil.
Plantoils-Coconutoil,Corn,Palm,Peanut,Sunfloweroil.
-Waxes-Spermacti,Beeswax,Carnaubawax.-Waxes-Spermacti,Beeswax,Carnaubawax.
-Phospholipids-Lecithins,Cephalins,Plasmoalogens,Phosphatidyl
inositols,Sphingomyelins.
-Glycolipids-Kerasin,Phrenosin,Nervon,Oxynervon.
-Steroids-Cholesterol.
-Terpenes-Monoterpenes,Sesquiterpenes,Diterpenes,Triterpenes.
-Carotenoids-Lycopene,Carotenes,Xanthophylls.

9. Fatty acids
Fatty acids:Fatty acids are carboxylic acids with hydrocarbon side chains (4 to 36 carbon).
The fatty acids are broadly class
a) Saturated fatty acids: it contains only single carbon bond chain and a carboxylic group:
•E.g. Palmiticacid: CH
3
(CH
2
)
14
COOH
b) Unsaturated fatty acids: It also contains double bonds with single carbon bond and carboxylic
group. EgOleic acid (cisisomer): CH
3
CH=CH(CH
2
)
7
COOH.
Cyclic Fatty acids: containing ring in their structure E.g: Hydnocarpicacid.Cyclic Fatty acids: containing ring in their structure E.g: Hydnocarpicacid.
Essential Fatty acids: These acids can not be synthesized by the body and therefore should be
supplied in the diet. E.g. Linoleic acid, Linolenicacid, arachidonicacid.
Fats: Fats are esters of fatty acids and glycerin also called triacylglycerols.
Simple Triacylglycerol contains the same fatty acid in all three positions. E.g. Tripalmitin.
Mixed triacylglycerol: they contain two or more different fatty acids.

10. Fatty acids(cont.)
•Tests to determine purity of fat sample are acid value (rancidity
measurement), Saponification number (fatty acid measurement),
Iodine number (unsaturation measurement) and Reichert-Meissl
number (volatile fatty acid measurement).
•Phospholipids: They contain phosphoric acid in addition to alcohol,
nitrogen base and fatty acids eg. Phosphotidicacid.
•Glycolipids: It contains three different molecules, namely amino •Glycolipids: It contains three different molecules, namely amino
alcohol, fatty acid and a carbohydrate eg. Nervon
•Lipoproteins: Molecular complexsof lipids and proteins are called
as lipoproteins. The protein part is called apoproteinthe major
functions are transport and delivery of the lipids.
•Steriods: Compounds containing cyclopentano
perhydrophenanthrenenucleus in their structreare called as
steroids. eg. Cholesterol, aldosterol.

11. Biological role of lipids
BiologicalRoleofLipids
1.Foodmaterial:Lipidsprovidefood,highlyrichincalorificvalue.Onegramlipid
produces9.3kilocaloriesofheat.
2.Foodreserve:Lipidsprovideareinsolubleinaqueoussolutionsandhencecanbe
storedreadilyinthebodyasafoodreserve.
3.Structuralcomponent:Lipidsareanimportantconstituentofthecellmembrane.3.Structuralcomponent:Lipidsareanimportantconstituentofthecellmembrane.
4.Heatinsulation:Thefatsarecharacterizedfortheirhighinsulatingcapacity.Great
quantitiesoffataredepositedinthesubcutaneouslayersinaquaticmammalssuchas
whaleandinanimalslivingincoldclimates.
5.Fattyacidabsorption:Phospholipidsplayanimportantroleintheabsorptionand
transportationoffattyacids.
6.Hormonesynthesis:Thesexhormones,adrenocorticoids,cholicacidsandalso
vitaminDareallsynthesizedfromcholesterol,asteroidallipid.

12. Biological role of lipids(cont.)
7.Vitamincarriers:Lipidsactascarriersofnaturalfat-solublevitaminssuchasvitaminA,D
andE.
8.Bloodcholesterollowering:Chocolatesandbeef,especiallythelatterone,werebelievedto
causemanyheartdiseasesastheyarerichinsaturatedfattyacids,whichboostcholesterollevels
inbloodandclogthearterialpassage.ButresearchesconductedattheUniversityofTexasby
ScottGrundyandAndreaBonanome(1988)suggestthatatleastonesaturatedfattyacidstearic
acid,amajorcomponentofcocoabutterandbeeffat,doesnotraisebloodcholesterollevelatall.acid,amajorcomponentofcocoabutterandbeeffat,doesnotraisebloodcholesterollevelatall.
Theresearchersplaced11menonthreecholesterolpoorliquiddietsforthreeweekseachin
randomorder.Oneformulawasrichinpalmiticacid,aknowncholesterolbooster;thesecondin
oleicacid;andthethirdinstearicacid.Whencomparedwiththedietrichinpalmiticacid,blood
cholesterollevelswere14%lowerinsubjectsputonthestearicaciddietand10%lowerinthose
ontheoleicaciddiet.
9.Antibioticagent.Squalamine,asteroidfromthebloodofsharks,hasbeenshowntobean
antibioticandantifungalagentofintenseactivity.Thisseemstoexplainwhysharksrarely
contractinfectionsandalmostnevergetcancer

13. Chemical structure of Lipids

14. Thank You