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