lipids www.themegallery.com

By Dr. Batoul Izzularab 3 4

lipids The lipids are the large group of naturally occurring organic compounds that are related by their solubility in non polar organic solvents (soluble in ether, chloroform , acetone, benzene) and general insoluble in water . lipids are heterogeneous group of water insoluble (hydrophobic ) organic molecules that can be extracted from tissue by nonpolar solvents. Because of their insolubility in aquas solutions, body lipids are generally found compartmentalized , as in the case of membrane – associated lipids or droplets of triglycerol in adipocytes, or transported in plasma in association with protein , as in lipoprotein particles .

Properties of lipids Organic compounds, water insoluble, but soluble in organic solvents (non polar solvents such as ether) Colorless Odorless Tasteless

Important of lipids: Lipids are important energy source , its storage in adipose are unlimited Lipids are important source of fat soluble vitamins, essential fatty acid and prostaglandins Lipids act as thermal and traumatic insulator Lipids act as support for internal tissue as kidney and mesentry of small intestine Non polar lipids acts as electrical insulator allowing propagation of depolarization waves along the myelinated nerve tissues Lipoproteins and phospholipids are important component of plasma cell membrane Lipids deals with serious medical problems as obesity , hypercholesterolemia and atherosclerosis

Chemistry of lipids Biological molecules that are insoluble in aquas solution and soluble in organic solvents it classified into Simple lipids Complex (compound) lipids Derived lipids

Simple lipids: Simple lipids are the ester of fatty acids with alcohol they are of two type , triglycerides and waxes

Complex , compounds or conjugated lipids These are simple lipids contain in addition to fatty acids and alcohol another non lipids group named prosthetic group according to the group , conjugated group of lipids are classified into Phospholipids: contain phosphate group Glycolipids : contain carbohydrate Lipoprotein : contain protein.

Derived lipids There are substance derived from hydrolysis of lipids e.g. fatty acids , glycerol, and also substance associated with lipids as sterol , steroids, fat soluble vitamins, fatty aldhyde and keton bodies.

Fatty acids (F.As) Fatty acids fill two major roles in the body: As the components of more complex membrane lipids As the major components of stored fat in the form of triacylglycerol

Fatty acids (F.As) Fatty acids are long chain hydrocarbon molecules containing a carboxylic acids moiety at one end (4-24 chain long) the numbering of carbon in fatty acids begins with the carbon of carboxylate group. At physiological PH , the carboxylic group are readily ionized rendering a negative charge onto fatty acids in body fluids.

Fatty acids (F.As) Fatty acids that contain no carbon –carbon double bond are termed saturated fatty acids, those that contain double bond are unsaturated fatty acid. The numeric designations used for fatty acids come from the number of carbon atoms , followed by the number of sites of unsaturation (e.g., palmitic acid is 16 carbon fatty acids with no unsaturation and is designated by 16:0) the site of unsaturation in fatty acid is indicated by symbol ∆ or ω and the number of the first carbon of the double bond (e.g. palmitolleic acids is a 16 – carbon fatty acids with one site of unsaturation between carbons 9 and 10 , and is designated by 16:1∆9) or (16:1,ω9).

Physical properties of fatty acids: Saturated fatty acid contain only single c-c bond of less than 10 carbon atoms are liquid at physiological temperature , wheres those containing more than ten are closely paked due to strong more than ten are closely packed due to strong attractions between chain , have high melting point and solids at room temperature.

Physical properties of fatty acids: Unsaturated fatty acids contain one or more double c═c bonds significantly lower melting point relative to saturated fatty acids due to non liner chains that do not allow molecules to pack closely and few interaction between chains , so they are liquid at room temperature Solubility in water decrease as the chain of F.A becomes longer they are completely soluble in water up to 6 C acids

Classification of fatty acid according to nutrition The majority of the body fatty acids are acquired in the diet .However the lipids biosynthetic capacity of the body (fatty acids synthase and other fatty acid modifying enzymes) can supply the body with all the various fatty acid structure needed . two key exception to this are the highly unsaturated fatty acids known as linoleic acids and linolenic acids , containing unsaturated sites beyond carbon 9 and 10 . these two fatty acids cannot be synthesized from precursors in the body , and are thus considered the essential fatty acids ;

Classification of fatty acid according to nutrition essential in the sense that they must be provided in the diet . Since plants are capable of synthesing linoleic and linolenic acids human can acquire these fats by consuming a Varity of plants or else by eating the meat of animals that have consumed these plant fat . Arachidonic acid can be formed from linoleic acids in the arachidonic acids is considered as non essential

Chemical properties of fatty acids: Ester formation F.As react with alcohol to form esters the most important is the reaction with glycerol to form triacylglycerols (neutral fats: oils or fats)

Chemical properties of fatty acids: 2-Salt formation : F.As react with alkalis to form the corresponding salt (soaps)

Chemical properties of fatty acids: Reduction : By reduction F.As give the corresponding fatty aldehydes , then fatty alcohols

Chemical properties of fatty acids: Properties due to prensence of double bonds: Addition of hydrogen to give the coorsponding saturated fatty acids

Chemical properties of fatty acids: Addition of Iodine Each double bond react with two iodine atoms

Chemical properties of fatty acids: Addition of oxygen The presence of double bond makes fatty acids sensitive to oxidation that react with oxygen to form ketone and aldehyde

Chemical properties of fatty acids:

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