Bioorganic Lipids 12/5/2019 Dr Seemal Jelani Chem-160

Introduction Structurally heterogeneous class of bioorganic compounds include diverse types of molecules as Fats and oils Waxes Cholesterol and its derivatives Some vitamins Prostagladins All of them have limited solubility in water 12/5/2019 Dr Seemal Jelani Chem-160

Lipids are esters of long chain fatty acids and alcohols. Monomer : Fatty acids are lipids’ building blocks Definition: It can be defined as nonpolar organic compound insoluble in polar solvent but soluble in organic solvents such as benzene ,ether, chloroform and boiling alcohol. Biological role of lipids: Lipids are found naturally in all living organisms. 1) It represents in cell structure and has a structural function in the cell. It is present in cell membranes. 2) An essential source of energy in the body. It gives more energy than carbohydrate and proteins.

Characteristics of Lipids Large class of water-insoluble bioorganic compounds In humans and many animals excess carbohydrates and other energy-yielding foods are converted to, and stored in the body as lipids known as fats This is a major way of storing chemical energy and carbon atoms in the body 12/5/2019 Dr Seemal Jelani Chem-160

Lipids function as covering for nerve fibres Fats and other lipids surround and insulate vital body organs, providing protection from mechanical shock and helping to maintain correct body temperature Lipids function as covering for nerve fibres Basic structural components of all cell membranes Many chemical messengers in the human body “ hormones” are lipids 12/5/2019 Dr Seemal Jelani Chem-160

Classification By structure: Simple: fats, oils, waxes, steroids. Complex: phospholipids, spingolipids, glygolipids. The derivatives: hormones, fat-solubility vitamins On the basis of whether they undergo hydrolysis reactions in alkaline solution: Saponifiable lipids can be hydrolyzed under alkaline conditions to yield salts of fatty acids. Nonsaponifiable lipids do not undergo hydrolysis reactions in alkaline solution. 12/5/2019 Dr Seemal Jelani

Lipids Lipids at a Glance Glycerol esters Hydrolysis products Saponifiable lipids Can be hydrolysed under alkaline conditions Nonsaponifiable Lipids Glycerol esters Hydrolysis products Non Glycerol esters Not a Hydrolysis products 12/5/2019 Dr Seemal Jelani Chem-160

Waxes Triacylglycerols Fats and Oils 12/5/2019 Dr Seemal Jelani Chem-160

Phosphoacylglycerols Sphingolipids 12/5/2019 Dr Seemal Jelani Chem-160

Nonsaponifiable Lipids Steroids Fat Soluble vitamins Eicosanoids Terpenes Pheromones 12/5/2019 Dr Seemal Jelani Chem-160

Structure and occurrence Fatty acids are monocarboxylic acids that contain long, unbranched hydrocarbon chains generally 12 to 26 carbon atoms in length They are rarely found free in nature but rather occurs mostly in esterified form in the structure of Saponifiable lipids 12/5/2019 Dr Seemal Jelani Chem-160

Fats can be divided according to their chemical composition to: Simple lipids: These compounds are: esters of fatty acids with glycerol. The triacylglycerol (TAG) is the simplest and most common fat. It is the form in which lipids are stored in the cell.

Saturated fatty acid Hexadecanoic acid (Palmitic acid) 12/5/2019 Dr Seemal Jelani Chem-160

Alternative notations Condensed and Sawtooth Condensed structure 12/5/2019 Dr Seemal Jelani Chem-160

Monounsaturated fatty acids 12/5/2019 Dr Seemal Jelani Chem-160

Trans 12/5/2019 Dr Seemal Jelani Chem-160

Saturated and unsaturated fatty acids 12/5/2019 Dr Seemal Jelani Chem-160

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Polyunsaturated fatty acids Omega-3 and Omega-6 Fatty acids Multiple double bonds 12/5/2019 Dr Seemal Jelani Chem-160

Omega-3 and Omega-6 Fatty acids important in human body chemistry Classification The basis for the omega classification system involves the following considerations A fatty acid has two ends Methyl (CH3) end Carboxyl (COOH) end 12/5/2019 Dr Seemal Jelani Chem-160

O CH3-(CH2)4-(CH=CH-CH2)4-(CH2)2-C OH Methyl end Carboxyl end 12/5/2019 Dr Seemal Jelani Chem-160

This is the way by which tracking of fatty acids is done In omega classification system, the carbon chain is numbered beginning at the methyl end, which is the reverse of the usual way. This reverse numbering system is used because of the mechanism by which fatty acid carbon chains are lengthened during biotransformations within the body Lengthening involves adding carbon atoms, two at a time at the carboxyl end of the chain This is the way by which tracking of fatty acids is done 12/5/2019 Dr Seemal Jelani Chem-160

Omega-3 and Omega-6 Fatty acids Polyunsaturated fatty acid with its endmost double bond three carbons away from its methyl end Omega-6 Fatty acids Polyunsaturated fatty acid with its endmost double bond six carbons away from its methyl end 12/5/2019 Dr Seemal Jelani Chem-160

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Lauric acid Palmitic acid Myristic acid Palmitoleic acid 12/5/2019 Dr Seemal Jelani Chem-160

Essential Fatty acids Needed by the human body and must be obtained from dietary sources because they cannot be synthesized within the body from other substances Essential fatty acids: 1 Linoleic acid 2 Linolenic acid 12/5/2019 Dr Seemal Jelani Chem-160

Linoleic acid and Linolenic acid Both are 18-carbon polyunsaturated acids Linoleic acid is an omega-6 acid Linolenic acid is an omega-3 acid 12/5/2019 Dr Seemal Jelani Chem-160

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Both contribute to proper membrane structure Deficiency of Linoleic acid Skin reddens and become irritated, infection and dehydration occur and liver may develop abnormalities and conditions will reverse on the restoration of the fatty acid 12/5/2019 Dr Seemal Jelani Chem-160

EPA (Eicosapentaenoic acid) DHA (Docosahexaenoic acid) Both of these are starting points for the synthesis of a variety of other longer-chain polyunsaturated acids which are: EPA (Eicosapentaenoic acid) DHA (Docosahexaenoic acid) Arachidonic acid major precursor of eicosanoids (substances that help regulate blood pressure) 12/5/2019 Dr Seemal Jelani Chem-160

EPA (Eicosapentaenoic acid) DHA (Docosahexaenoic acid) Both of them are important constitutes of the communication membranes of the brain and its normal development, and also active in the retina of the eye Sources: Vegetable oils, meat and fish live in deep cold water are good source of linoleic acid and other omega-6 acids 12/5/2019 Dr Seemal Jelani Chem-160