CHEMISTRY OF LIPIDS Lecture 2 PDF

 -Triacyl glycerol ( TAG) or neutral fat belongs to the class simple lipids - Triacylglycerols are composed of a glycerol  backbone to which 3 fatty acids are esterified. CH2OH  CH2O OCR1 CHOH +...

 -Triacyl glycerol ( TAG) or neutral fat belongs to the class simple lipids - Triacylglycerols are composed of a glycerol  backbone to which 3 fatty acids are esterified. CH2OH  CH2O OCR1 CHOH + 3 Fatty acids  CHO OCR2 CH2OH  CH2O OCR3 Glycerol Triacylglycerols  - TAGs or Neutral fats are classified into two subgroups: Oils: these are liquid due to their high content of USFA, e.g. corn, cotton seed and soya been oils. Fats: these are solid due to their high content of SFA, e.g. margarine. Hardening: is the hydrogenation of oils to form solid fats (margarine). This process involves conversion of USFA to SFA. Phospholipids belongs to the class compound lipids - According to the alcohol present, phospholipids are classified into: Phosphoglycerides: containing glycerol. Sphingomyelin: containing sphingosine. ❖ Phosphatidic acid ❖ Lecithin (phosphatidyl choline) ❖ Cephalin (phosphatidyl ethanolamine) ❖ Phosphatidyl serine. FA ❖ Lipositol (Phosphatidyl inositol ) FA P+? Sphingomyelin differs from other types of phospholipids in  containing the amino alcohol sphingosine, and no glycerol.  1. Phospholipids are amphipathic molecules containing nonpolar parts (fatty acid side chains) and polar parts (phosphate, serine, ethanolamine, choline and inositol). Thus they form micelles in water.  2. They are good emulsifying factors. During digestion they produce emulsification of dietary fats and help in their digestion by pancreatic lipase.  3. Phospholipids are important constituents of cell membranes.  4.Phospholipids are important constituents of plasma lipoproteins which act as carriers of different types of lipids in blood.  Lysophospholipids: are formed by the action of phospholipase A2 on lecithin or cephalin to form lysolecithin and lysocephalin. Phospholipase A2 removes the fatty acid in position 2.  Snake venom: contains lecithinase enzyme which, when injected into blood, converts phospholipids present in the cell membrane of red cells to lysophospholipids. This produces hemolysis of red cells and subsequent death if not treated by antitoxins.  Classification of steroids: ❖ Sterols eg. cholesterol. ❖ Bile acids. ❖ Steroid hormones: glucocorticoids, mineralocorticoids and sex hormones. Synthesis:  1-Primary bile acids are synthesized from cholesterol  in the liver. 2-Secondary bile acids are synthesized by the action of  intestinal bacteria on the primary bile acids in the intestine. Bile acids are conjugated in bile with glycine or taurine  and sodium, then secreted in bile in the form of bile salts. - Function: bile salts are important for the emulsification of fats; thus help in the digestion and absorption of fats.