LIPIDS and their functions and classification

LIPIDS
FUNCTIONS OF LIPIDS
Classification of Lipids
CHEMICAL PROPERTIES OF SIMPLE LIPIDS

1. WELCOME

2. Submitted to:- Dr. H. S. Bhadauria Asso Professor, Dept. of GPB SDAU, S.K. Nagar Submitted by:- Vaghela Gauravrajsinh K M.Sc. (Agri.) Reg.no:-04-AGRMA-01840-2018 SDAU, S.K. Nagar LIPIDS Course Title :- Principles of Plant Physiology

3. LIPIDS Fats and their derivatives are known collectively as lipids. (Greek word: lipos= fat) The word lipids is derived from the Greek word “ lipos ” meaning fat . The principal component of lipid is fatty acid . The term lipid was first time given by biochemist BLOOR in 1943. Bloor defined lipid as “Naturally occurring compound which are insoluble in water and soluble in organic solvents such as benzene, chloroform, ether etc. On hydrolysis they yield fatty acids .” Lipids are defined as chemically heterogeneous group of compounds of biological importance that are relatively insoluble in water but freely soluble in non-polar solvents such as chloroform, benzene, ether, hot alcohol, acetone, etc .

4. FUNCTIONS OF LIPIDS Storage form of energy (triglycerides). It is a concentrated source of energy as it provides more than twice energy (9 kcal/ g) as compared to carbohydrates(4 kcal/ g). Structural components of bio membranes (phospholipids and cholesterol). Provide essential fatty acids (EFA) viz, linoleic, linolenic and arachidonic acids Metabolic regulators (steroid hormones and prostaglandins). Act as surfactants, detergents and emulsifying agents (amphipathic lipids). Act electric insulators in neurons. Provide insulation against changes in external temperature (subcutaneous fat). Give shape and contour to the body. Protect internal organs by providing a cushioning effect (pads of fat). Help in absorption of fat soluble vitamins (A, D, E and K). Improve taste and palatability of food. Contribute aroma through nose and texture of food which is responsible for the mouth feel .

5. Classification of Lipids Simple lipids Compound lipids Derived lipids Lipid complexed to other compounds

6. Classification of Lipids Lipids Simple Lipid Compound Lipids Sterols Hydrocarbon Vitamin Fat, Oil Wax Cholesterols A, D, E & K Phopho Lipids Glyco Lipids Ganglioside Lipo Protein Lecithin Cerebrosides N-acetyl Neuramic Acid + Protein + Triglyceride + Cephalic Fatty acid + Hexoses Cholesterols or Phosho Lipids

7. Simple Lipids Compound Lipids Derived Lipids Esters of fatty acids with glycerol and monohydric alcohols. Esters containing chemical groups in addition to alcohol and fatty acids. Substances derived from simple and compound lipids by hydrolysis. Alcohols, fatty acids, aldehydes, ketones, sterols and hydrocarbons Depending upon the constituent alcohols they are further subdivided into fats or oils and waxes. Depending upon the chemical groups they are further subdivided into phospholipids, glycolipids, sulpholipids and lipoproteins. ----- Waxes are esters of fatty acids and alcohols other than glycerol Glycolipids contain hexose units preferably galactose along with fatty acids and alcohol e.g. Cerebrosides. ----- e.g .,Plant wax-carnauba wax; Insect wax-beeswax. Plant sulpholipids contain sulphated hexose with fatty acids and alcohol ----- Animal wax – lanolin Lipoproteins contain protein subunits along with lipids. Depending upon density and lipid compound they are further classified as VLDL, LDL and HDL. -----

8. SIMPLE LIPID Simple lipids are the esters of fatty acids with various long chain alcohols. Fatty acids are of two types. Saturated Fatty acids. Unsaturated fatty acids . SATURATED FATTY ACIDS Butyric acid CH 3 CH 2 CH 2 COOH Butter Caproic acid CH 3 (CH 2 ) 4 COOH Butter Caprylic acid CH 3 (CH 2 ) 6 COOH Coconut , palm oil Lauric acid CH 3 (CH 2 ) 10 COOH Laurel , kernel oil Myristic acid CH 3 (CH 2 ) 12 COOH Nutmeg oil Palmitic acid CH 3 (CH 2 ) 14 COOH Palm oil Stearic acid CH 3 (CH 2 ) 16 COOH Cocoa butter Arachidic acid CH 3 (CH 2 ) 18 COOH Peanut oil .

9. UNSATURATED FATTY ACIDS Oleic acid ( C 18 ) One double bond Olive oil Linoleic acid (C 18 ) Two double bond Linseed oil, Soybean oil Linolenic acid ( C 18 ) Three double bond Linseed oil Erucic acid ( C 22 ) One double bond Mustard oil Arachidonic acid (C 20 ) One double bond Ground nut oil No . (B), (C) and (E) are the essential unsaturated fatty acids required by the human being.

10. COMPARISON OF FATS AND OILS FAT Esters of fatty acids + glycerol Solid at room temperature Low molecular weight More saturated fatty acids High saponification value Low iodine value OILS Esters of fatty acids + glycerol Liquid at room temperature High molecular weight Higher unsaturated fatty acids Low saponification value High iodine value

11. CHEMICAL PROPERTIES OF SIMPLE LIPIDS HYDROLYSIS :- They are hydrolyzed by super heated steam, strong alkali, dilute mineral acid or lipase enzyme . Lipids + H 2 O Fatty acid + glycerol Lipase enzyme SAPONIFICATION : - When fat or oil reacts with NaOH or KOH, they yield salts of fatty acid (soap) and glycerol. Neutral fat + NaOH / KOH Soap + glycerol HYDROGENATION :- Unsaturated fatty acids react with hydrogen in presence of nickel at 150-190 C to give saturated fatty acids. Liquid oil is converted to solid fat. Hydrogenation is the process used for preparing the artificial ghee (vegetable oil).   Unsaturated fatty acid + H2 Saturated fatty acid CH 3 (CH 2 ) 7 CH = CH CH 2 COOH CH 3 (CH 2 ) 7 CH 2 CH 2 CH 2 COOH

12. HYDROGENATION : Unsaturated fatty acids react with hydrogen in presence of nickel at 150-190 C to give saturated fatty acids. Liquid oil is converted to solid fat. Hydrogenation is the process used for preparing the artificial ghee (vegetable oil). Unsaturated fatty acid + H2 Saturated fatty acid CH 3 (CH 2 ) 7 CH = CH CH 2 COOH CH 3 (CH 2 ) 7 CH 2 CH 2 CH 2 COOH HALOGENATION : When unsaturated fat is treated with halogens (I 2 / Br 2 / Cl 2 ), the fat is converted to halogenated compounds. E.g . Iodine value is a useful tool to know the amount of unsaturation in the fat. CH 3 (CH 2 ) 7 CH= CH CH 2 COOH + I 2 / Br 2 /Cl 2 CH 3 (CH 2 ) 7 CH - CH CH 2 COOH I/Br/Cl I/Br/Cl Halogenated compound

13. RANCIDITY :- When butter/oil/fat is stored for a long time , they often become rancid due to hydrolysis/oxidation. The rancid fat gives off flavour, bad smell and unpleasant taste. The rancidity can be defined as the production of bad unpleasant smell in oil or fat is called rancidity .   The rancidity is of two types . Hydrolytic rancidity Oxidative rancidity Aldehydic rancidity Ketonic rancidity 1. Hydrolytic rancidity :- This is developed by the action of microbial lipase enzyme which split the triglycerides and produce low molecular weight (C 4 – C 10 ) fatty acid such as butyric acid. This butyric acid produces bad smell in the butter . Butter or butterfat + Lipase + 3H 2 Glycerol + Butyric acid 2. Oxidative rancidity :- This type of rancidity develops due to oxidation of unsaturated fats to produce either the cleavage or polymerisation of fatty acid. Two types of oxidative rancidity a) Aldehydic rancidity b) Ketonic rancidity

14. 1) Aldehydic rancidity: There is production of peroxides when these peroxides are converted into aldehyde which gives bad smell in fat. O – O HC = CH + O2 - C - C C = O H H H Unsaturated fatty acid Peroxide Aldehyde 2) Ketonic rancidity: When ketones are formed from the β oxidation of saturated fatty acid, then keto acids are formed. Elimination of CO 2 leads to rancid ketone formation to produce bad smell . CH 3 (CH 2 ) n COOH CH 3 CH 2 - CH 2 – C – COOH Saturated fatty acid Keto acid O CH 3 CH 2 CH 2 COCH 3 Ketone (bad smell)

15. COMPOUND LIPIDS They are the complex esters of aliphatic mono carboxylic fatty acid with aliphatic alcohols having nitrogenous base such as choline, ethanolamine etc. 1) PHOSPHOLIPIDS:- These are the esters produced by the combination of fatty acid, glycerol, phosphoric acid and a nitrogenous base. E.g. Lecithin, Cephalic, Plasmlogens, Phosphoinositis, Sphingomyelins LECITHIN :- They are found in the growing tissues, egg yolk, brain, kidney, soybean, nervous tissues, blood etc. They are occurring in two isomeric forms. a) α - Lecithin and b) β – Lecithin CEPHALIN : - The difference between lecithin and cephalin is only in the structure. Choline residue is replaced with the cholamine, attached to glycerol. Their main function is in nervous tissues. Plasmalogen, phosphoinositides and Sphingomyelins are components in the human tissues and have little importance in the plants .

16. 2) GLYCOLIPID :- It contains carbohydrate moiety particularly galactose in the structure. E.g. Cerebroside is present in brain tissues and act as neuro transmitters. STEROLS Sterols are the solid alcohols with high molecular weight having many cyclic rings in the structure. ( Steros = solid ) , ( ol = alcohol ). They are widely distributed in plant, animals and micro organisms in conjugated form . CHOLESTEROL :- It is a animal sterol with a molecular formula of C 27 H 45 OH ERGOSTEROL :- It is a mycosterol with a molecular formula C 28 H 43 OH. Sistosterols or Stigmsterols : It is a phytosterol of plant origin .

17. METABOLISM OF LIPIDS 1. ANABOLISM:- Glucose Glucose Glycolysis Glycolysis Glyceraldehyde Pyruvic acid Glycerol Acetyl Co – A Fatty acid synthesis Glycerol + Fatty acid Lipid

18. 2. CATABOLISM :- Lipid Fatty acid + Glycerol Lipase β –oxidation Glycolysis Acetyl co-A Pyruvic acid Acetyl co -A TCA cycle TCA cycle CO 2 + H 2 O + ENERGY

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