General classification of lipids(presentation)

There explained is the basic classification of Lipids

1. Classification of lipids Lipids can be classified according to their hydrolysis products and according to similarities in their molecular structures.

2. Three major subclasses are recognized:

3. SIMPLE LIPIDS Fats and Oils Both types of compounds are called triacylglycerols because they are esters composed of three fatty acids joined to glycerol, trihydroxy alcohol. The difference is on the basis of their physical states at room temperature. It is customary to call a lipid a fat if it is solid at 25°C, and oil if it is a liquid at the same temperature. These differences in melting points reflect differences in the degree of unsaturation of the constituent fatty acids. Waxes Wax is an ester of long-chain alcohol (usually mono-hydroxy) and a fatty acid. The acids and alcohols normally found in waxes have chains of the order of 12-34 carbon atoms in length.

4. COMPOUND LIPIDS Phospholipids, may be glycerophospholipids or sphingophospholipid depending upon the alcohol group present (glycerol or sphingosine). Glycolipids, may also be glyceroglycolipids or sphingoglycolipid depending upon the alcohol group present (glycerol or sphingosine).

5. DERIVED LIPIDS They include fatty acid, glycerol, sphingosine and steroid derivatives. Steroid derivatives are phenanthrene structures that are quite different from lipids made up of fatty acids.

6. Alcohols and Esters The most important and frequently occurring alcohol found in lipids is glycerol. Glycerol is a small organic molecule consisting of three hydroxyls (OH-) groups. Glycerol makes up simple lipids which are esters of fatty acids and glycerol and similar alcohols. The alcohol might be glycerol or other long-chain alcohol. The long-chain alcohols are mostly mono-hydroxy with a single OH group. Depending on the alcohol used, simple lipids consist of fats, oil, or waxes. Fats and oils are esters of fatty acids and glycerol, whereas waxes are esters of fatty acids and long-chain alcohols. The esters of fatty acids are formed after the dehydration reaction between the fatty acids and the alcohol molecules. L

7. Fatty acids Fatty acids are hydrophobic compounds consisting of an aliphatic hydrocarbon chain terminating in a carboxylic acid moiety. Fatty acids can be unsaturated (i.e., fatty acids that contain one or more carbon–carbon double bonds) and saturated (i.e., fatty acids that do not contain any carbon–carbon double bond). There are studies reporting that fatty acids of fruits, vegetables, and mushrooms may contribute to the  in vitro   α- amylase and α- glucosidase inhibition activities of their extracts. Terpenoids or Terpenes :  A large group of lipids that are formed by repeating units called isoprenes or isoprenoid units (C 5 H 8 ) e.g. carotenoids, rubber, menthol, camphor, steroids, gibberellins, etc. Isoprene does not occur in nature but is available as isopentenyl pyrophosphate.

8. Carotenes :  Carotenes are terpenoids with a general formula of C 40 H 56 . In plants they function as accessory photosynthetic pigments, as attractants for animals to perform pollination and fruit dispersal and to help in plant growth movements. Lycopene is a simple carotene of red color that occurs in the ripe fruits of tomato and chilly. The most common carotene is β -carotene. Rich in carrot root and all leafy vegetables. β-carotene is converted to vitamin A in animals. Prostaglandins: A group of hormone-like derivative of unsaturated fatty acids which, function as messenger substances between cells, agents in blood clotting, smooth muscle contraction, allergic acid inflammatory reactions. Prostaglandins occur in human seminal fluid, menstrual fluid, amniotic fluid and a number of tissues and also circulate in blood.

9. Steroids: It is a group of tetracyclic lipid-derivatives. Sterols are alcoholic derivatives which possess one or more hydroxyl groups. The most common sterol is cholesterol. Steroid diosgenin obtained from Yam ( Dioscorea ) has property to prevent sperm formation in males. It is, therefore useful in producing male anti-fertility pill. Steroids are anabolic stimulants. They are misused for body building. Birth control tablets possess steroid hormone progesterone. Cholesterol: A fat soluble white crystalline sterol or steroid alcohol, C 27 H 45 OH. Found exclusively in animal food, especially meat, animal fat and egg yolk. Normal cholesterol concentration of blood is 140-250 mg/100 ml. Occurs both in free state as well as combined with fatty acids at its hydroxyl group at carbon 3.