Lipids - Biomolecules PDF

Biomolecules NBEM101T B.Sc. Biotechnology Course Credit - 3 Mr. Sourav Shukla Assistant Professor Department of Biotechnology and Bioengineering Institute of Advanced Research, Gandhinagar Unit – 6 Lipids Introduction LIPID d...

Biomolecules NBEM101T B.Sc. Biotechnology Course Credit - 3 Mr. Sourav Shukla Assistant Professor Department of Biotechnology and Bioengineering Institute of Advanced Research, Gandhinagar Unit – 6 Lipids Introduction LIPID describes a chemically varied group of fatty substances and are highly concentrated energy stores. They are water-insoluble bio-molecules but soluble in organic solvents such as ether, benzene, Chloroform, etc. They are esters of long chain fatty acids and alcohols. Lipids serve as fuel molecules, signal molecules, and components of membranes, hormones and intracellular messengers. They protect internal organs, serve as insulating materials and give shape and smoothness to the body. Accumulation of fat in liver is prevented by phospholipids. Lipid Function Membrane structure Essential fatty acids are useful for transport of Main structure of cell membranes cholesterol, formation of lipoproteins, etc. Regulate membrane permeability Phospholipids in mitochondria are responsible Cofactors for enzymes for transport of electron transport chain components. Vitamin K: blood clot formation Coenzyme Q: ATP synthesis in Phospholipids help in removal of cholesterol mitochondria from the body by participating in reverse cholesterol transport. Signalling molecules Cholesterol is a constituent of membrane Paracrine hormones (act locally) structure and it synthesizes bile acids, hormones Steroid hormones (act body-wide) and vitamin D. It is the principal sterol of higher Growth factors animals, abundant in nerve tissues and gallstones. Vitamins A and D (hormone precursors) Pigments Color of tomatoes, carrots, pumpkins, some birds Antioxidants Classification of Lipids based on Biological Functions Storage Lipids—The principle stored form of energy, like TAG, Wax, etc. Fats and oils are composed of 3 fatty acids each in ester linkage with a single glycerol (Triacylglycerols) Waxes are esters of long-chain(C14-C36) saturated and unsaturated fatty acids with long chain (C16-C30) alcohols Structural Lipids– The major structural elements of Biological Membranes, like Phospholipids, Sphingolipids, etc. Classification of Lipids based on Chemical Composition 1. SIMPLE LIPIDS: These lipids are the esters of fatty acids with alcohols. They are of three types: Waxes, sterol esters and Triacylglycerol. 2. COMPOUND/COMPLEX LIPIDS: These lipids are esters of fatty acids with alcohols & with additional groups such as phosphate, nitrogenous base, etc. They are again divided into 3 types: Phospholipids, Glycerophospholipids, Sphingophospholipids. 3. DERIVED LIPIDS: These lipids are obtained on hydrolysis of simple and complex lipids. These lipids contain glycerol and other alcohols. This class of lipids include steroid hormones, ketone bodies, hydrocarbons, fatty acids, fatty alcohols, mono and diacylglycerides. 4. MISCELLANEOUS LIPIDS: These include compounds, which contain characteristics of lipids. They include squalene, terpenes, hydrocarbons, carotenoids, etc. TAG Ester of glycerol with three fatty acids. Non polar, hydrophobic molecules, essentially insoluble in water It is also called neutral fat. They are stored in adipocytes in animals and endosperm and cotyledon cells in plants. A mammal contains 5% to 25% or more of its body weight as lipids,90%TAG Basic Phospholipid Structure Wax Waxes are esters of long chain (C14-C36) saturated and unsaturated fatty acids with long chain (C16-C30) alcohols. Functions – Chief storage fuels for some of the microorganisms. Protect skin and hair. Prevents excess water evaporation in plants. Protects against parasites Application in industries, pharmaceuticals, and cosmetics Fatty Acids Fatty acids are composed only of carbon, hydrogen and oxygen in the proportion of 76%, 12.6% and 11.3% respectively. Fatty Acids are carboxylic acids with hydrocarbon chains ranging from 4-36. Fatty acids are of 2 types: Saturated and Unsaturated. Saturated Fatty Acids have no double bonds and thus the hydrocarbon chain is completely unbranched Unsaturated fatty acids contain one or more double bonds, usually in the cis- conformation. Polyunsaturated fatty acids have 2-6 double bonds.  Fatty Acids Saturated FA Unsaturated FA Lauric Acid (12:0) MUFA PUFA Myristic Acid (14:0) Palmitoleic Linoleic Acid Palmitic Acid (16:0) Acid (16:1 Δ9) (18:2 Δ9,12) Oleic Acid Stearic Acid (18:0) Linolenic Acid (18:1 Δ9) (18:3 Δ9,12,15) Arachidic Acid (20:0) Arachidonic Acid (20:4 Δ5,8,11,14) Nomenclature CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2- 14:0 tetradecanoic acid COOH 12 11 10 9 8 7 6 5 4 3 2 1 16:0 Hexadecanoic acid 20:0 Eicosanoic acid OR 22:0 Docosanoic acid CH3 (CH2)10 – COOH Dodecanoic acid (Lauric) 24:0 Tetracosanoic acid No double bonds for e.g., in 18:0, Octadecanoic acid If one double bond then acid Octadecenoic acid If two double bonds then Octadecadienoic acid If three double bonds Octadecatrienoic acid. The most common positions for double bonds are Δ9, Δ12, and Δ15. In almost all the naturally occurring unsaturated fatty acids, the double bonds are in Cis- configuration Physical Properties The physical properties of fatty acids are largely determined by the length and degree of unsaturation of the hydrocarbon chain. The longer the chain and the fewer the double bonds, the lower is the solubility in water, and higher is the melting point. Addition of double bonds decreases the melting point whereas, increasing the chain length increases the melting point. For example: 12:0 MP 44.20C, 16:0 MP 62.70C, 18:1 MP 10.50C, 18:2 MP -5.00C, 18:3 MP - 110C. Trivial names of fatty acids refer to the natural sources of derivation: eg Lauric (12:0) isolated from seed fat of Lauraceae Myristic (14:0) –seed fat Myristaceae Palmitic (16:0) –seed fat of palmae Oleic (18:1) –seed fat of olive oil. Saturated Trans, similar to Cis one curved Cis two curved Linear structure linear structure structure structure MP – 69.60C MP – 420C MP – 10.50C MP – -5.00C Membrane Fluidity  Compound Lipids Phosphoglycerides Sphingolipids Cholesterol Phosphatidyl Choline Sphingomyelin Cholesterol (Lecithin) Phosphatidyl Ethanolamine Cerebroside Ergosterol (Cephalin) Phosphatidyl Inositol Ganglioside Sitosterol Phosphatidyl Serine Stigmasterol Brassica sterol Sphingolipids  Compound Lipids Phosphoglycerides Sphingolipids Cholesterol Phosphatidyl Choline Sphingomyelin Cholesterol (Lecithin) Phosphatidyl Ethanolamine Cerebroside Ergosterol (Cephalin) Phosphatidyl Inositol Ganglioside Sitosterol Phosphatidyl Serine Stigmasterol Brassica sterol Cholesterol Cholesterol is a derived lipid. Its widely distributed as sterols in animals and humans Its an essential component of cell membrane Vit. D, hormones and bile acids are synthesized from cholesterol. Bile acids are essential for normal digestion and absorption of fats and fat-soluble vitamins. Most of the cholesterol is synthesized by the liver An increase in dietary intake of cholesterol, increases its synthesis in the body as well which leads to coronary heart diseases. Unsaturated fats reduce the level of cholesterol in blood. Cholesterol HDL, LDL and VLDL Low density lipoproteins (LDL) transports cholesterol from liver through blood to the tissues (Bad cholesterol) High density lipoprotein (HDL) transports cholesterol from blood to the liver where it is metabolized (Good cholesterol) LDL Cholesterol  High risk of heart attack HDL Cholesterol  Low risk of heart attack VLDL - Chylomicrons Effect on Blood Saturated Fat Omega-3 Fat – Increases total cholesterol – Decreases total – Increases LDL-cholesterol cholesterol Polyunsaturated Fat – Decreases LDL- cholesterol – Decreases total cholesterol – Increases HDL- – Decreases LDL-cholesterol cholesterol – Decreases HDL-cholesterol – Decreases serum triglycerides Monounsaturated Fat Trans Fat – Decreases total cholesterol – Increases total – Decreases LDL-cholesterol cholesterol – Increases HDL-cholesterol – Increases LDL-cholesterol Thank You!