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Home , Valeric acid

❖ are organic compounds formed mainly from alcohol and fatty acids combined together by linkage.

❖ Lipids are biological molecules that are insoluble in water but soluble in nonpolar solvents (ether, chloroform, benzene, acetone).

❖ Lipids are the waxy, greasy, or oily compounds found in plants and animals. BIOLOGICAL IMPROTANCE OF LIPIDS

❖ They are more palatable and storable compared to carbohydrates. ❖ They have a high-energy value (25% of body needs) ❖ They provide more energy per gram than carbohydrates and proteins, but carbohydrates are the preferable source of energy.

❖ Supply the essential fatty acids that cannot be synthesized by the body. ❖ Supply the body with fat-soluble vitamins (A, D, E and K). ❖ They are important constituents of cell membrane and nervous system. BIOLOGICAL IMPROTANCE OF LIPIDS

❖ Stored lipids “depot fat” is stored in all animal cells act as • A store of energy. • A pad for the internal organs to protect them from outside shocks. • A subcutaneous thermal insulator against loss of body heat. ❖ Lipids provide bases for dealing with diseases such as obesity, atherosclerosis, -storage diseases, essential deficiency, and respiratory distress syndrome. CLASSIFICATION OF LIPIDS

contain

contain 2 types of components (a contain > 2 types of components fatty acid & an alcohol) (a fatty acid, an alcohol & others) FATTYACIDS ❖ a fatty acid is a with a long aliphatic chain, which is either saturated or unsaturated. FATTYACIDS Properties: • The long, nonpolar hydrocarbon tails of fatty acids are responsible for most of the fatty or oily characteristics of lipids. • The carboxyl (COOH) group is hydrophilic (polar) under basic conditions, such as physiological pH (7.4) • Fatty Acid Micelles

Micelles are important in the transport of insoluble lipids in the blood FATTYACIDS Characteristics: • The chain length ranges from 4 to 30 ; 12-24 is most common. • The chain is typically linear, and usually contains an even number of carbons • The many fatty acids which occur naturally arise primarily through variation of chain length and degree of saturation

• There may be one double bond or many, up to six in important fatty acids. FATTYACIDS Characteristics: • When double bonds occur they are almost always cis • If there is more than one double bond, they occur at three- intervals

e.g., -C=C-C-C=C-

• This is called divinylmethane pattern. FATTY ACIDS - Classification based on number of double bonds & Nomenclature • If without double bonds: Saturated Fatty Acids • If with double bonds: Unsaturated Fatty Acids o 1 double bond: Monounsaturated fatty acids o 2 or more double bonds: Polyunsaturated fatty acids List of some Saturated Fatty Acids Structural Common Name Systematic Name Lipid Numbers Formula

Propionic acid Propanoic acid CH3CH2COOH C3:0

Butyric acid Butanoic acid CH3(CH2)2COOH C4:0

Valeric acid Pentanoic acid CH3(CH2)3COOH C5:0

Caproic acid Hexanoic acid CH3(CH2)4COOH C6:0

Caprylic acid Octanoic acid CH3(CH2)6COOH C8:0

Capric acid Decanoic acid CH3(CH2)8COOH C10:0

Myristic acid Tetradecanoic acid CH3(CH2)12COOH C14:0

Palmitic acid Hexadecanoic acid CH3(CH2)14COOH C16:0

Stearic acid Octadecanoic acid CH3(CH2)16COOH C18:0 List of some Mono-Unsaturated Fatty Acids Common Name Chemical Name Lipid Numbers cis-Tetradec-9-enoic acid 14:1 (n-5) cis-Hexadec-9-enoic acid 16:1 (n-7) cis-Octadec-9-enoic acid 18:1 (n-9) (trans-oleic acid) trans-Octadec-9-enoic acid 18:1 (n-9) 11-Eicosenoic acid (gondoic acid) cis-Eicos-11-enoic acid 20:1 (n-9)

Common Name Lipid Numbers Chemical Name

List of some Omega-3 Poly-Unsaturated Fatty Acids Alpha-linolenic acid 18:3 (n-3) all-cis-9,12,15-octadecatrienoic acid 20:5 (n-3) all-cis-5,8,11,14,17-eicosapentaenoic acid 22:6 (n-3) all-cis-4,7,10,13,16,19-docosahexaenoic acid List of some Omega-6 Poly-Unsaturated Fatty Acids 18:2 (n-6) all-cis-9,12-octadecadienoic acid Gamma-linolenic acid 18:3 (n-6) all-cis-6,9,12-octadecatrienoic acid FATTY ACIDS – Melting Property • Shorter fatty acids usually have lower melting points than longer ones ( [18C] = 70ºC, [16C] = 63ºC)

• The cis-double bonds in unsaturated fatty acids put an inflexible “curve” in the carbon chain, preventing the molecules from packing together as tightly as saturated fatty acids do. STRUCTURE OF FATS AND OILS TRIGLYCERIDES

• Animal fats and vegetable oils are esters composed of three molecules of a fatty acid connected to a glycerol molecule, producing a structure called a triglyceride or a triacylglycerol TRIGLYCERIDES

• The fatty acids in a triglyceride molecule are usually not all the same; natural triglycerides are often mixtures of many different triglyceride molecules TRIGLYCERIDES • Fats are triglycerides that are solids at room temp. – usually derived from animals & mostly saturated fatty acids • Oils are triglycerides that are liquids at room temp. – usually derived from plants or fish & mostly unsaturated fatty acids TRIGLYCERIDES - Hydrolysis WAXES

• Waxes are simple lipids contain a fatty acid joined to a long-chain alcohol, 12-32 carbons. WAXES • Waxes are insoluble in water, and not as easily hydrolysed as fats and oils. • They often occur in nature as protective coatings on feathers, fur, skin, leaves, and fruits. • Sebum, secreted by the sebaceous glands of the skin, contains waxes that help to keep skin soft and prevent dehydration. • Waxes are used commercially to make cosmetics, candles, ointments, and protective polishes. PHOSPHOGLYCERIDES • Phosphoglycerides are complex lipids that are major components of cell membranes. • Phosphoglycerides and related compounds are also called phospholipids. PHOSPHOGLYCERIDES - Aminoalcohols • The most abundant phosphoglycerides contain the alcohols choline, ethanolamine, or serine attached to the phosphate group. PHOSPHOGLYCERIDES – (Aminoalcohol) – Lecithin • Phosphoglycerides that contains the aminoalcohol ‘choline’ are called lecithins.

• The fatty acids at the first and second positions are variable, so there are a number of different possible lecithins. • They act as an emulsifying agent PHOSPHOGLYCERIDES – (Aminoalcohol) – Cephalin • Phosphoglycerides that contains the aminoalcohol ‘ethanolamine or serine’ are called cephalin.

• Cephalins are found in most cell membranes and are particularly abundant in brain tissue. • They are also found in blood platelets and play a role in blood-clotting. SPHINGOLIPIDS • Sphingolipids are complex lipids that contain sphingosine instead of glycerol. SPHINGOLIPIDS - Spingomyelin • One important type of sphingolipds are the sphingomyelins.

SPINGOMYELIN

• Sphingomyelins are found brain and nerve tissue, and in the myelin sheath that protects nerves SPHINGOLIPIDS - Spingomyelin

• Sphingomyelins - a bilayer that wraps around nerve cell axons SPHINGOLIPIDS - Glycolipids • Glycolipids are sphingolipids that contain carbohydrates (usually monosaccharides) • They are also referred to as cerebrosides because of their abundance in brain tissue

Cerebroside BIOLOGICAL MEMBRANES - Membrane Structure STERIODS • are classified as lipids because they are soluble in nonpolar solvents, but they are non-saponifiable because the components are not held together by ester linkages • The basic structure contains four fused rings • There are three important types of steroids: 1) Cholesterol 2) Steroid hormones 3) Bile salts STERIODS - Cholesterol • Cholesterol is the most abundant steroid in the body. • it is manufactured in the liver. • It is an essential component of cell membranes, and is a precursor for other steroids, such as the bile salts, sex hormones, vitamin D, and the adrenocorticoid hormones. STERIODS – Steroid hormones

• Hormones, molecules that regulate the function of organs and tissues, come in a variety of forms. • Some, such as sex hormones and adrenocorticoid hormones, are steroids • Sex hormones produced in the testes and ovaries regulate the production of sperm and eggs and aid in the development of secondary sex characteristics e.g.: testosterone, , progesterone • Adrenocorticoid hormones are produced in the adrenal glands (located on the top of the kidney) E.g.: Glucocorticoids - Cortisol and its derivatives, cortisone and prednisolone STERIODS - Bile Salts • Bile is a yellowish brown or green fluid produced in the liver and stored in the gall bladder. PROSTAGLANDINS • Prostaglandins are cyclic compounds synthesized from . Like hormones, they are involved in a host of body processes, including reproduction, blood clotting, inflammation, and fever. • Prostaglandins have a wide range of biological effects: – causing pain – causing inflammation – causing fever – affecting blood pressure – inducing labor (PGE2)