Lipids

Lipids

1. Organic compounds containing C, H, O and they are insoluble in water but soluble in fat solvents as alcohol ether benzene and chloroform

   • Simple lipids
     • Esters of fatty acids and alcohols, they are classified according to alcohol
       • Triglycerides(neural fat) : with glycerol
       • Waxes: esters of fatty acids with long chain alcohol higher than glycerol
     • Fatty acids
       • monocarboxylic acids and have even number of C atoms
         • Saturated
           • No double bond e.g: Palmitic acid
         • Unsaturated
           • Monoethenoid. One double bond e.g Oleic acid
           • Polyethenoid Contain more than one double bond
             • Essential fatty acids should be supplied in diet.
               • Diethenoid F.A.: Linoleic
               • Triethenoid F.A: Linolenic
               • Tetraethenoid F.A: Arachidonic
                 • It's the precursor of important group of lipids known as prostaglandins
   • Compound lipids
     • More complicated than simple as it contains fatty acid + alcohol and other group(simple + group)
       • Phospholipids
         • They contain F.A + alcohol + phosphoric acid.
           • Phosphatidic acid
             • It's the precursor of all phospholipids containing glycerol
               • On hydrolysis gives glycerol + sat F.A. + unsat F.A. + phosphoric acid
           • Lecithin
             • Is present in cell membrane and acts as a lung surfactant
               • On hydrolysis gives glycerol + sat F.A. + unsat F.A. + phosphoric acid + choline base
           • Cephalins
             • Mixture of phosphatidyal serine, ethanolamine and inositol. present in liver and brain
           • Cardiolipin
           • Sphingomyelin
       • Glycolipids
       • Proteolipids
   • Derived lipids
     • They are produced by hydrolysis of simple or conjugated lipids or they are associated with lipids in nature
       • Fatty acids
       • Alcohols
         • Glycerol in TAG
         • Phosphoglycerides
       • Steroids
       • Fat soluble vitamins
         • Bile acids: They are hydroxyl derivatives of C24 steroid termed as cholanic acid
           • Primary bile acid: These are formed in the liver from cholesterol
             • Chenodeoxy cholic acid
             • Cholic acid
           • Secondary bile acid: formed by the action of bacteria in the large intestine on primary bile acid
             • Deoxycholic acid
             • Lithocholic acid
           • Bile salt, formed by conjugation of primary bile acids with glycine(80%) or taurine(20%), then they're excreted in bile as sodium
             • Importance
               • Conversion to bile salts is an important mechanism for removal of cholestrol from blood
               • Emulsification of fat in the intestine
               • Prevent precipitation of cholesterol in bile and formation of cholesterol stones
               • Stimulate liver to secrete more bile (choleretic effect)