chem of lipids

7/29/2019 chem of lipids

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CHEMISTRY OF LIPID


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INTRODUCTION

Lipids are a chemically diverse group of compounds.

Insoluble in water & soluble in non-polar solvents

like chloroform, ether and benzene.

Hydrophobic in nature.

It include fats, oils, steroids, waxes & related

compounds.

DEFINITION They are esters of fatty acids with alcohol or are

substances capable of forming such esters & are


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CLASSIFICATION

A. Simple lipid.

B. Complex or compound lipid.C. Derived lipid.

A. Simple lipid

Esters of fatty acids with various alcohols. Classified as following depending on the type of

alcohol present-

i. Neutral fats.ii. Waxes.


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1.NEUTRAL FATS Esters of fatty acids with alcohol glycerol.

eg tripalmitin.

Uncharged.2. WAXES

a. True waxes:-

These are esters of fatty acids with highermolecular weight monohydric long chain alcohol.

eg- lanolin (from lamb,s wool).

Bees-wax

spermacetic oil ( from whales).

b. other waxes:- Esters of fatty acid with alcohol.

eg:- Cholesterol forms cholesterol ester.

Retinol form vitamin A ester

Cholecalciferol (vitamin D) forms vitamin D ester


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B. COMPLEX LIPID

These are esters of fatty acid with alcohol containing

additional (prosthetic ) groups.

Classification:- according to the type of prostheticgroup present:-

a) Phospholipids

b) Glycolipidsc) Lipoproteins.


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a. Phospholipids

They contain phosphoric acid & frequently a nitrogenous

base as additional group. Classification:- on the basis of the type of alcohol

present:-

1. Glycerophospholipids.

2. Sphingophospholipids.


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1. Glycerophospholipids

The alcohol present is glycerol. Eg:-

I. Phosphatidyl choline (lecithin)

II. Phosphatidyl ethenolamine (cephalin)

III. Phosphatidyl serine

IV. Phosphatidyl inositol

V. LysophospholipidVI. Plasmalogen

VII. Cardiolipins.

2. Sphingophospholipids

The alcohol present in sphingosine.

Eg:- Sphingomyelins.


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b. Glycolipids

Additional residue are carbohydrate with

nitrogenous base.Eg:- Cerebrosides

Gangliosides.

c. Lipoproteins

Lipoproteins are formed by combination of lipid with

a prosthetic group protein.

Eg:- Chylomicrons

Very low density lipoprotein(VLDL) Low density lipoprotein(LDL)

High density lipoprotein(HDL)


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C. DERIVED LIPIDS

Include the products obtained after the hydrolysis

of simple & compound lipids. Eg:- Fatty acids

Glycerol

Steroids

Cholesterol

Vitamins A & D.


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FUNCTION

Storage form of energy.

Structural lipid.eg:- phospholipid, glycolipid,& sterols.

Cholesterol is a precursor of many steroid hormones.

Activators of enzymes: eg:- glucose-6 phosphatase,mono-oxygenases & mitochondrial enzyme B-hydroxybutyric dehydrogenase, requirephophatidylcholine for activation.

Help in absorption of fat soluble vitamin & act as asolvent for the transport of the fat soluble vitamin.

In the mitochondria cardiolipin is necessary for optimum

function of electron transport process.

Phosphatidyl inositol triphosphate is serve as a keyprecurser in the formation of a second messenger.

Steroid hormone & prostaglandins are modulator of

physiological activity.


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Nervous tissue are particularly rich in lipids which serve

an important role in their function.

Bile salt derived from cholesterol act as a emulsifying

agent & facilitate the digestion & absorption of lipids.

Important dietary consituents.

Non polar lipids act as electrical insulator.

Thermal insulator in the subcutaneous tissue & certainorgans.


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FATTY ACIDS

Fatty acid are carboxylic acid with hydrocarbon chains &

represented by a chemical formula R-COOH. The fatty acid are amphiphatic in nature.

Fatty acid occurs mainly as esters of glycerols in neutral fat &

oil.

Classification:- Four major classes:-

A. Straight chain fatty acid

B. Branched chain fatty acid

C. Substituted fatty acidD. Cyclic fatty acid


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A. Straight chain fatty acid :-

Fatty acid in which the carbon are arranged linearly.

Sub classified into two classes:-

1. Saturated fatty acid

2. Unsaturated fatty acid

1. Saturated fatty acids:- There is no double bond in thehydrocarbon chain of these fatty acids ,so can be packed together

into a compact structure.

It is sub classified into :-

a. Even carbon acid:- palmitic acid & stearic acid. b. Odd carbon acid:- Propionic acid.


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2. Unsaturated fatty acid:- They contain double bond

in their hydrocarbon chains.

They are in cis configuration.

Sub classified into following type according to the

number of double bonds present in the structure.

a. Monounsaturated fatty acid

b. Poly unsaturated fatty acid

c. Ecosanoids .

B. Branched chain fatty acid:- eg. Isovaleric acid &Isobutyric acid.


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C. Substituted fatty acid:- In this one or more hydrogen

atom have been replaced by another group.

Eg: Lactic acid, cerebronic acid

D. Cyclic fatty acid:- eg. Prostaglandins.


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Essential fatty acids (EFA) Human can not synthesize 2 main types of PUFA.

Linolenic acid & Linoleic acid . Arachidonic acid , fatty acid derived from linoleic acid is an

essential precursor of regulatory lipids eicosanoids in man ,which include :- Prostaglandins, Thromboxanes, Prostacyclin,leukotrines.

FUNCTION OF EFA:- 1. Synthesis of eicosanoids 2. Maintenance of structural integrity

3. Development of retina & brain

4. Antiatherogenic effect

5. Transport of cholesterol & formation of lipoproteins.

Deficiency of EFA:- 1. Phrynoderma or toad skin. 2. Dermatitis

3. Poor wound healing


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CHOLESTEROL:- cholesterol is the major sterol in

animal tissues. but not in the plant fats. It consists of

steroid nucleus (CPP). fUNCTIONS:- Major structural constituent of cell

membrane & plasma lipoproteins.

Precursors of :-

steroid hormones.

Bile acids

Vitamin D

chem of lipids

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