Lipid Chemistry PDF

Lipid Chemistry By Dr. Heba Marey  Lipid Chemistry Lipids are a heterogeneous group of compounds related to fatty acids. Lipids are relatively insoluble in water. They are soluble in nonpolar solvents such as ether, chloroform or benzene. Classificati...

Lipid Chemistry By Dr. Heba Marey  Lipid Chemistry Lipids are a heterogeneous group of compounds related to fatty acids. Lipids are relatively insoluble in water. They are soluble in nonpolar solvents such as ether, chloroform or benzene. Classification: lipids are classified into simple, complex (compound), and derived lipids Classification: Simple Compound Derived Fats Phospholipids: Fatty acids (acylglycerols) Glycerophospholipids Steroids Waxes (Higher Sphingophospholipids Fat soluble vitamins alcohol + FA) Glycolipids Ketone bodies Cerbrosides Carotenoids Gangliosides Ceramide oligosaccharides Functions (biomedical Importance): 1-In diet: Lipids are important constituent of diet due to: a.They are a source of high energy value. b.They contain fat soluble vitamins. c.They contain essential fatty acids. d.They make diet palatable. 2-In the body: ‫اﻷﻧﺴﺠﺔ اﻟﺪﻫﻨﻴﺔ‬ a. Lipids in adipose tissue serve as storage form of energy. b. They serve as thermal insulator in the subcutaneous tissues. c. Nonpolar lipids act as electrical insulator, allowing rapid propagation of waves along myelinated nerves. d. Lipoproteins (a combination of fat and proteins) are important because: They enter in the structure of cell membranes and They serve as a transport form of energy in the blood. e. Neutral lipids: are those which carry no charges and include: Neutral fats (acylglycerols). Cholesterol and cholesteryl esters  Fatty Acids (R. COOH) They are water-insoluble long chain hydrocarbons. They may be saturated (containing no double bonds) or unsaturated (containing one or more double bonds). They are mostly monocarboxylic i.e. having one carboxyl group at the end of the chain (-COOH). Fatty acids occur mainly as esters in natural fats and oils. Fatty acids may also present as free fatty acids in the plasma. The numbering of carbons in fatty acids begins with the carbon of the carboxylate group. Classification of fatty acids: 1.Saturated fatty acids: Have no double bonds in the chain as palmitic (16 C) and stearic (18 c) Their general formula is CH3- (CH2)n-COOH 2.Unsaturated fatty acids: they contain double bonds a. Monounsaturated fatty acids i.e. contain one double bond e.g. palmitoleic acid b. Polyunsaturated fatty acids (essential fatty acids): Containing more than one double bond: e.g linoleic acid arachidonic acid. Nutritional Classification: A. Nonessential fatty acids: 1. These are fatty acids which can be synthesized in the body. Thus, they are not necessary to be obtained from the diet. 2. They include all saturated and monounsaturated (one double bond) fatty acids as palmitoleic and oleic acid. 3. They can be synthesized from acetyl CoA (active acetate) derived from glucose oxidation. B. Essential fatty acids: Definition: These are fatty acids that cannot be synthesized in the body. They must be obtained from the diet. They include fatty acids that contain more than one double bond (polyunsaturated fatty acids), e.g. lenoleic, linolenic and arachidonic acids. Sources: a.Plant oils e.g. corn oil, soya bean oil, sunflower, linseed oil and cotton seed oil. b.Fish oils: shark liver oils, which particularly contain the ω3 polyunsaturated fatty acids. Importance: Essential fatty acids are important for: a. Normal growth. b.They enter in the structure of phospholipids and cholesterol esters. c.They enter in the structure of cell membranes and are required for the fluidity of membrane structure. d.They protect against atherosclerosis and coronary heart disease by decreasing free cholesterol and LDL. e.Arachidonic acid (20C) is a precursor of a group of compounds called: eicosanoid. Properties of fatty acids: Physical properties: 1- Solubility: a.Short chain fatty acids are soluble in water. b.Long chain fatty acids are insoluble in water but soluble in nonpolar fat solvents. 2- Melting point: It depends on the length of the chain of fatty acids and the degree of unsaturation, so: a.Short chain and unsaturated fatty acids are liquid at room temperature. b.Long chain saturated fatty acids are solid at room temperature