lipids-structure and classification.pptx

7/23/2019 lipids-structure and classification.pptx

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Lipids

1


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Lipids

Lipids are esters of long chain fatty acids

They are insoluble in waterand soluble in

nonpolar solventssuch as acetone, alcohol, ether

or chloroform.

Their low water solubility is due to a lack of

polarizing atoms such as N, S, and P


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Lipids

Lipids are composed of , !, "# long hydrocarbon chains $!%&

'(amily groups)# fats

# phospholipids

# steroids


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Functions of lipids Storage form of energy

*mportant dietary components because of their highenergy value and also because of the fat%soluble

+itamins and the essential fatty acids contained inthe fat of natural foods.

Structural components of biomembranes

Ser+e as thermal insulators in the subcutaneous

tissues and around certain organs

Nonpolar lipids act as electrical insulators,allowingrapid propagation of depolarization wa+es along

myelinated nerves


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Functions of lipids(Contd.)

Pro+ide shape and contour to the body

ct as metabolic regulators

ombinations of lipid and protein $lipoproteins&are important cellular constituents, occurring bothin the cell membraneand in the mitochondria,and ser+ing also as the means of transporting

lipidsin the blood.


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Biological roles of lipids:


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Lipid functions

Lipids are used in

Fuel storage

Hormones

Signal transduction messenger

Membranes

Membrane lipids:

Phospholipid

Glycolipid

Cholesterol


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Classification:


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Classification-loor in /01

*. Simple2 fats, oils, wa3es, steroids.

**. ompound2

. Phospholipids containing phosphoric acids2

& Nitrogen containing glycerophosphatides

0& Non 4nitrogen containing glycerophosphatides

5& Plasmalogens, containing long chain alcohol

6& Phospho sphingosides, containing sphingosine.

-. Non phosphorylated lipids2

& 7lycosphingolipids$carbohydrates&

0& Sulpholipids or sulfatides.

***. 8eri+ati+es2 cholesterol and steroids

*9. Lipids comple3ed to other compounds2 lipoproteins


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Types of Lipids

Lipids with fatty acids# Fats and oils (trigycerides)

# Waxes# Phospholipids

# Sphingolipids

Lipids without fatty acids# Steroids

10


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Classification of Lipids


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Fatty acids:

Stearic Oleic

Fatty acids areused as storedforms of energy incells.

A fatty acidis acarboxylic acid

with a longunbranched nonpolar hydrocarbontail.


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Classification of fatty acids:

Depending up on the total number of carbon atom

Even chain: even number of carbons- most of the

naturally occurring

Odd chain : odd number of carbons- microbial cell walls,

in mil

Depending on the length of hydrocarbon chain:

Short chain: ! to "

#edium chain: $ to 1%

&ong chain: 1"-!%


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#edium-chain 'atty (cid

)"-10 carbons*

&ong-chain 'atty (cid

)1! or more carbons*

Short-chain 'atty (cid

)less than " carbons*

The Length of the Carbon Chain


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Classification of fatty acids:

Fatty acids

Saturated FA Unsaturated FA


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Saturated fatty acids: Saturated fatty contains only single bonds.

Saturatedindicates that the maximumpossible number of hydrogen atoms arebonded to each carbon.

Considered as harmful. It increases total cholesterol level and TGs

level.

Hypercholestrolemic SAs are !yristic acid "

#auric acid.


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Saturated fatty acids:

(ll + bonded to o +.+ double bonds

long, straight chain

most animal fats : palmitic andstearic acid

High melting points

solid at room temp.

/ contributes to cardiovascular

disease )atherosclerosis*

. plaue deposits


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Source$Harper%sIllustrated&iochemistry by'obert(.

!urray)*arryl (.Granner)+eter A.

!ayes),ictor -


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Unsaturated fatty acids:

/ Fatty acids contain one or more C=C double bonds.

/ The double bonded C prevent the molecules from

packing tightly together

/ onlinear chains do not allo! molecules to pack

closely

/ "F# include oleic acid and linoleic acid.


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Unsaturated Fatty Acids

Lo! melting points

li$uid at room temperature

%lant & fish fats

'egetable oils


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Saturated and Unsaturated FattyAcids

(aturated = C)C bonds

"nsaturated = one or more C=C bonds

C**H

C**H

palmitoleic acid, an unsaturated fatty acid

palmitic acid, a saturated acid


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Fatty cids

Unsaturated Fatty Acids

Saturated Fatty Acids

20:4

18:3

18:2

18:1

16:1

20:0

18:0

16:0

14:0

12:0

Carbon Atoms:Double Bonds

Melting Point(C)

CommonName

-49

-11

-5

16

1

77

70

63

58

44

Arachidonic acid

Linolenic acid

Linoleic acid

Oleic acid

Palmitoleic acid

Arachidic acid

Stearic acid

Palmitic acid

Myristic acid

Lauric acid

Higher mp

Lower mp


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+lassification based on unsaturation:

+onoethenoid acids: one double bond eg: oleic acid

iethenoid acids: wo double bonds

eg: &inoleic acid

Triethenoid acids: hree double bonds

eg: &inolenic acidTetraethenoid acids: 'our double bonds

eg: (rachidonic acid


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Saturated Vs. unsaturatedsaturated

unsaturated


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Divisions of unsaturated fatty acids:

onounsa ura e a y


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onounsa ura e a yAcid

!/A0 One carbon-carbon double bond 'ound mostly in vegetable oils such as olive,

canola, and peanut2

hey are considered as beneficialfor humanhealth2


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Monounsaturated fatty acids:

Cis F# Trans F#


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Cis fats Trans Fats

aturallyoccurring

3es hydrogenation, or4hardening,5 of natural

oils

ealth Effect / Decreases total cholesteroland 6s level2

/ 7ncreases D& level2

Detrimental 8 lowersgood cholesterol andincreases the level ofbad cholesterol in the

body2 armful to hearthealth could causecardiac death2

(rrangement ofatoms he chains of carbon atomsare on the same side of thedouble bond, resulting in ain

ydrogen atoms are onthe opposite side of thedouble bonds of thecarbon chain, maingthe fat moleculestraight


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Hydrogenation of Fatty acids:

/ ydrogenation of oils leads to solidification and saturation

e2g2 9anaspathi


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Cis-fatty acid: Hs on same side of the double bond; fold into a U-like formation; naturally occurring;

Trans-fatty acid: Hs on opposite side of double bond; more linear; occur in partially hydrogenated foods;


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rans-fatmustbe

listedon'ood&abel

:y;anuary

1,!00"


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Polyunsaturated Fatty Acid


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Polyunsaturated Fatty Acid(PUFA)

#ore than one carbon-carbon double bond carbons away from themethyl end.omega > '(

" carbons from methyl end.omega " '(


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Omega-

Omega-!


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Eicosanoids: Derived from long chain

polyenoic fatty acids )Eicosa- !0

+arbon arachidonic acid*2

considered @local hormones5

participating in intercellular

signaling,

EAamples:


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Essential fatty acids


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Essential fatty acids urr and urr in 1>0

'atty acids that have to be supplied in the diet

(ll these are polyunsaturated fatty acids

he + !0 fatty acid (rachidonic acid )!0:%?,$,11,1%*

he two +1$ acids

&inoleic acid )1$:!? ,1!* F (lso called 9itamin '

&inolenic acid )1$:>? ,1!,1*2


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Omega-

Omega-!


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)eboo - medicine* iochemistry 6arrettand 6risham !nd ed

(ource: iochemistry by 6arrett and 6risham !nd ed


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Triglycerides


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Triglycerides(TG):/ The simplest lipids constructed from fatty

acids are the triacylglycerols.

/ Also referred to as Triglycerides Fats or

!eutral fats.

/ A signi1cant number of the fatty acids inplants and animals exist in the form of

triacylglycerols./ It is composed of three fatty acids each in

ester lin2age with a single glycerol

Triacylglycerols are


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Triacylglycerols arenon"olar#.

/ Structure:

F glycerol($% alcohol) &fatty acid

/ Triacylglycerols are non"olar$ +olar hydroxyls of

glycerol and the polar carboxylates of the fatty acids arebound in ester lin2ages

dehydration synthesis

H*


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Triglycerides(TG):/ Ester lin'age et*een +, - %++,/ #ipids have lower speci1c gravities than water3so

4oats on the a5ueous phase


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Fatty acid com"osition ofthree food fats.


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Ty"es of triacylglycerol

/ Sim"le triacylglycerol$ same 2ind of fatty acid in allthree positions

F 6xamples$

/Tristearoylglycerol

tristearin03derived fromthree units of stearic acid

/ Trioleoylglycerol triolein03 three units of theunsaturated fatty acid oleic acid

/ /i0ed triacylglycerols : contain two or threedi8erent fatty acids. e g: 12"aimitoyl23$2distearin.

/ !ost of natural plant and animal fat is composed ofmixtures of simple and mixed triacylglycerols.


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E0am"le of triglycerides

F Triglyceride deri"ed from one molecule each of palmitic

acid# oleic acid# and stearic acid# the three most abundant

fatty acids in the biological $orld%

%,3+%(%,3)14%,$

%,3+%(%,3)15%,$

%,$(%,3)6%,%,(%,3)6%+%,

+

+

+

oleate (18:1)

stearate (18:0)

palmitate (16:0)


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riglycerides

'unctions Energy source

1 g yields about >$ ;2

'orm of stored energy in

adipose tissue

7nsulation and protection

+arrier of fat-soluble vitamins

Sensory properties in food


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(aponification and (oap

ydrolysis with alali is called saponification

riglycerides split into glycerol and the salts of

fatty acids

he salts of fatty acids are /soaps0

1*H gives softer soaps


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(aponification

23 a34* C 5CH.678CH2

*

CH

CH. *H

*H

CH.

*H

CH

CH.

CH. *

*

*

C 5CH.679CH2

*

C

*

5CH.679CH2

5CH.679CH2C

*

3 2 a*H

salts of fatty acids 5soaps6


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Triglyceride eactions

Triglycerides undergo three basic reactions

These reactions are identical to those studied in

carbo&ylic acids

riglyceride

6lycerol

'atty (cids6lycerol

'atty (cid Salts

#ore saturated

triglyceride

!O, G

aO

!, i


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Hydrolysis


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(aponification


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Hydrogenation


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PLS! L"P"#S$

Lipoproteins2

Pl li id


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Plasma lipids$

Total plasma lipid is 6::%;::mg


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Lipoproteins:

"1

&i i


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&ipoproteins:

&ipids absorbed from the diet and synthesiHed by the liver

and adipose tissue must be transported between various

cells and organs for utiliHation and storage2

&ipids are insoluble in water, the problem of transportation inthe aueous plasma is solved by associating nonpolar lipids

)triacylglycerols and cholesteryl esters* with amphipathic

lipids )phospholipids and cholesterol* and proteins to maewater-miscible lipoproteins2

; l ( f i i


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;eneral (tructure of Lipo proteins

Some apolipoproteins are integral and cannot be removed, whereas others

can be freely transferred to other lipoproteins2

Li t i $L &


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Lipoproteins$Lp&

9arious combinations of lipid and protein produce particlesof different densities2

Depending on the density ) ultra centrifuge* or

electrophoretic mobility- ypes:12 +hylomicron

!2 9ery low density lipoprotein ) 9&D&*

>2 7ntermediate density lipoprotein )7D&*

%2 &ow density lipoprotein )&D&*

2 igh density lipoprotein )D&*


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%lassification of Lipoproteins

Lipoproteins with high lipid content will ha+e low density, larger size andso float on centrifugation.

Those with high protein content sediment easily, ha+e compact size andha+e a high density.


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li i


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polipoproteins$

polipoproteins are lipid%bindingproteins in the blood.

responsible for the transport of Triacylglycerols phospholipids

cholesterol and cholesteryl esters between

organs.

*t combine withlipids to formse+eral classes of lipoprotein

particles. =ainly synthesized in li+er> small

?uantities in almost all organs.

i f li i


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Functions of polipoproteins$

Structural role$-6@ is an importantcomponent.

ctivation of en&ymes$po %'"" is acti+ator of lipoprotein

lipasepo ' acti+ateslecitin

cholesterol acetyltransferase(L%*)

+eceptor binding$po ' is the ligand for #L

receptor

%hylomicrons


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%hylomicrons

(ormed in the intestinal mucosal cells% contain apo-'./and apo'but apo'%and apo'0are added fromserum.

bsorbed into2 the lymph +essels, then %%A

mo+es into the bloodBich in2 T7s!alf life about hour.Function$ 8eli+er T7Cs to

dipose tissue 4for storage heart and muscle cells to be used as fuel

! b li f h l i


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!etabolism of chylomicron$

&p&

9L8L $9ery Low 8ensity


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9L8L $9ery Low 8ensityLipoprotein&

Synthesi&ed in$ the li+er from glycerol and fattyacids

ontains apo -::, %** and D

Secreted into2 the bloodstream!alf life2 to 5 hours

Bich in2 T7s

(unction2 8eli+er T7s to body cellsSimilar to hylomicrons, but made by different

tissues

+etabolism of chylomicron:


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/ LpL$ Lipoprotein

Lipase en&yme,

located at endothelial

layer of capillaries of

adipose tissue,

muscles and heart.

+etabolism of chylomicron:


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1L#L 2 Lipoprotein cascade pathway$

/ 9&D& F maCor carriers of

endogenous 6s)synthesiHed in

liver* to peripheral tissues2/ 9&D& contain F hepatic

cholesterol, apo -100, +-77 and E/ alf life is 1-> hours

/ 7n peripheral tissues apo +-77activates &p& , which liberates '(

/ he remnant is called

7D&) intermediate density

lipoprotein*

/ 7D& contains less (6 I morecholesterol2

/ Small part of 7D& is taen up by

liver and maCor fraction is

converted to &D&

Lipoprotein)


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Lipoprotein)

=ade in2 the Li+er as 9L8L Bich in cholesterol E contains 4 apo -%::rise from2 9L8L once it has lost a lot of its

T7Cs E apo D Secreted into2 the bloodstream

!al life2 0 days. ontain F1G of plasma cholesterol. (unction2 8eli+er cholesterol to all body

cells -ad cholesterol$

"3idized L8L creates pro%coagulantssurface on the endothelium, causingblood clot formation.


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/ &D& concentration in blood has a positive correlation with

incidence of cardiovascular disease2

#L(i h # it Li t i )


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#L(igh #ensity Lipoprotein)

Pick up cholesterol from body cells and take it backto the li+er H 're+erse cholesterol transport)

Latter e3creted through bile

Potential to help re+erse heart disease!8L le+el below 51mg


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!etabolism of #L

+ole of L%*LT$ Lecithin holesterol cyl Transferase&

enzyme catalyzes the esterification of cholesterol toform holesteryl ester.

The reaction can be represented as follows%

Lecithin I holesterol Lysolecithin Iholesteryl Dster

!etabolism of #L


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!etabolism of #L

LT and the LT acti+ator apo %*Jbind tothe discoidal particles, and the surfacephospholipid and free cholesterol areconverted into cholesterol esters andlysolecithin

The nonpolar cholesteryl esters mo+e into thehydrophobic interior of the bilayer, whereaslysolecithin is transferred to plasma albumin.

Thus, a nonpolar core is generated, forming aspherical, pseudomicellar !8L co+ered by a

surface film of polar lipids and apolipoproteins. This aids the remo+al of e3cess unesterified

cholesterol from lipoproteins and tissues .

+eferences$


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+eferences$

. Lehninger Principles of -iochemistry (ourth Ddition by

8a+id L. Nelson and =ichael =. o3

0. Te3t book of biochemistry by 8= 9asude+an and

Sreekumari S

5. =edicine -iochemistry 0ndedition by 7arrett and 7risham

6. olor tlas of -iochemistry Second edition,by Kan oolman

and laus%!einrich Boehm

1. -iochemistry the chemical reactions of li+ing cells by 8a+id

l

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lipids-structure and classification.pptx