Lipids PDF

Lipids Lipids biomolecules that contain fatty acids or a steroid nucleus soluble in organic solvents but not in water named for the Greek word lipos, which means “fat” extracted from cells using organic solvents grouped according to their chemical composition derivatives of fatty acids...

Lipids Lipids biomolecules that contain fatty acids or a steroid nucleus soluble in organic solvents but not in water named for the Greek word lipos, which means “fat” extracted from cells using organic solvents grouped according to their chemical composition derivatives of fatty acids Lipids Functions of Lipids principal stored forms of energy hormones structural elements of biological provide satiety value membranes contribute to the palatability of insulation and padding foods enzyme cofactors protein sparer emulsifying agents in the carrier of fat-soluble vitamins digestive tract Fatty Acids free fatty acids hydrocarbon derivatives 4 to 36 carbons long ester or amide linkage characteristics of FFA monocarboxylic acid even number of carbon atoms saturated or unsaturated branched and substituted Fatty Acids Fatty Acids Fatty Acids – Physical Properties saturated fatty acids fit closely together in a regular pattern saturated fatty acids are usually solids at room temperature unsaturated fatty acids - the cis double bonds cause the carbon chain to bend or kink, giving the molecules an irregular shape unsaturated fats are liquid oils at room temperature Fatty Acids – Physical Properties Fats and Oils - Triacylglycerols in the body, fatty acids are stored as fats and oils known as triacylglycerols also called triglycerides triesters of glycerol (a trihydroxy alcohol) and fatty acids Fats and Oils - Triacylglycerols three hydroxyl groups on glycerol form ester bonds with the carboxyl groups of three fatty acids Fats and Oils - Triacylglycerols major form of energy storage for animals fat solid at room temperature comes from animal sources such as meat, whole milk, butter, and cheese usually contain more saturated fatty acids oil liquid at room temperature obtained from a plant source large amounts of fatty acids with two or more double bonds (unsaturated) Fats and Oils - Triacylglycerols chemical reactions of the triacylglycerols (fats and oils) are the same as those we alkenes hydrogenation of an unsaturated fat hydrogen is added to one or more carbon–carbon double bonds to form carbon–carbon single bonds Fats and Oils - Triacylglycerols chemical reactions of the triacylglycerols (fats and oils) are the same as those we alkenes hydrolysis in the presence of strong acids or digestive enzymes called lipases breaking of the ester bonds Fats and Oils - Triacylglycerols chemical reactions of the triacylglycerols (fats and oils) are the same as those we alkenes saponification occurs when a fat is heated with a strong base such as sodium hydroxide products are glycerol and the sodium salts of the fatty acids called as soaps Fats and Oils - Triacylglycerols Glycerophospholipids similar to triacylglycerols except that one hydroxyl group of glycerol is replaced by the ester of phosphoric acid and an amino alcohol bonded through a phosphodiester bond Glycerophospholipids amino alcohols found in glycerophospholipids are choline, serine, and ethanolamine Glycerophospholipids lecithins and cephalins particularly abundant in brain and nerve tissues as well as in egg yolks, wheat germ and yeasts Glycerophospholipids contain both polar and nonpolar regions, which allow them to interact with both polar and nonpolar substance most abundant lipids in cell membranes play an important role in cellular permeability make up much of the myelin sheath that protects nerve cells combine with the less polar triglycerides and cholesterol to make them more soluble as they are transported in the body Steroids: Cholesterol, Bile Salts, and Hormones compounds containing the steroid nucleus, which consists of three cyclohexane rings and one cyclopentane ring fused together Steroids: Cholesterol one of the most important and abundant steroids in the body, is a sterol because it contains an oxygen atom as a hydroxyl group on carbon 3 component of cellular membranes, myelin sheath, and brain and nerve tissue found in the liver, bile salts, and skin, where it forms vitamin D used to synthesize steroid hormones in the adrenal glands Steroids: Cholesterol obtained from eating meats, milk, and eggs synthesized by the liver from fats, carbohydrates, and proteins high levels of cholesterol are associated with the accumulation of lipid deposits (plaque) that line and narrow the coronary arteries saturated fats in the diet may stimulate the production of cholesterol by the liver Steroids: Bile Salts synthesized in the liver from cholesterol and stored in the gallbladder bile is secreted into the small intestine bile salts mix with the water-insoluble fats and oils in our diets emulsifying large globules of fat larger surface area for the lipases, enzymes, that digest fat also help in the absorption of cholesterol into the intestinal mucosa Steroids: Bile Salts Steroids: Steroid Hormones hormone comes from the Greek “to arouse” or “to excite” chemical messengers that serve as a kind of communication system from one part of the body to another closely related in structure to cholesterol and depend on cholesterol for their synthesis sex hormones and the adrenocortical hormones Steroids: Steroid Hormones male sex hormones, testosterone and androsterone promote the growth of muscle and facial hair maturation of the male sex organs and of sperm female sex hormones estrogens and progesterone direct the development of female sexual characteristics prepares the uterus for the implantation of a fertilized egg Steroids: Steroid Hormones male sex hormones, testosterone and androsterone promote the growth of muscle and facial hair maturation of the male sex organs and of sperm female sex hormones estrogens and progesterone direct the development of female sexual characteristics prepares the uterus for the implantation of a fertilized egg Steroids: Steroid Hormones Steroids: Steroid Hormones synthetic forms of the female sex hormones are used in birth-control pills anabolic steroids, derivatives of testosterone increase muscle mass and decrease body fat side effects including hypertension, fluid retention, increased hair growth, sleep disturbances, acne, liver damage and decreased sperm production Steroids: Adrenal Corticosteroids adrenal glands, located on the top of each kidney, produce the corticosteroids aldosterone a mineralocorticoid responsible for electrolyte and water balance by the kidneys cortisone a glucocorticoid increases the blood glucose level and stimulates the synthesis of glycogen from amino acids in the liver. Steroids: Adrenal Corticosteroids Steroids: Adrenal Corticosteroids synthetic corticoids - prednisone are derived from cortisone used medically for reducing inflammation and treating asthma and rheumatoid arthritis Lipoproteins lipids must be transported through the bloodstream to tissues where they are stored, used for energy, or transformed to hormones lipids are nonpolar and insoluble in the aqueous environment of blood made more soluble by combining them with glycerophospholipids and proteins to form water-soluble complexes lipoproteins spherical particles with an outer surface of polar proteins and glycerophospholipids that surround hundreds of nonpolar molecules of triacylglycerols and cholesteryl esters Lipoproteins Lipoproteins differ in density, lipid composition, and function chylomicrons and very low density lipoproteins (VLDLs) transport triacylglycerols, glycerophospholipids, and cholesterol to the tissues for storage or to the muscles for energy low density lipoproteins (LDLs) transport cholesterol to tissues where it is used for the synthesis of cell membranes, steroid hormones, and bile salts LDLs deposit cholesterol in the arteries “bad” cholesterol Lipoproteins high density lipoproteins (HDLs) remove excess cholesterol from the tissues and carry it to the liver, where it is converted to bile salts and eliminated “good” cholesterol Prostaglandins hormone-like substances produced in small amounts in most cells of the body also known as eicosanoids formed from arachidonic acid, the polyunsaturated fatty acid with 20 carbon atoms have potent physiological effects increase blood pressure, and others lower blood pressure. stimulate contraction and relaxation in the smooth muscle of the uterus. produce inflammation and pain Prostaglandins Waxes waxes are found in many plants and animals coatings of carnauba wax on fruits, leaves, and stems of plants help to prevent loss of water and damage from pests skin, fur, and feathers of animals provide a waterproof coating ester of a saturated fatty acid and a long-chain alcohol, each containing from 14 to 30 carbon atoms Waxes beeswax from honeycombs carnauba wax from palm trees are used to give a protective coating to furniture, cars, and floors jojoba wax is used in making candles and cosmetics such as lipstick lanolin, a mixture of waxes obtained from wool, is used in hand and facial lotions to aid retention of water, softening the skin Waxes beeswax from honeycombs carnauba wax from palm trees are used to give a protective coating to furniture, cars, and floors jojoba wax is used in making candles and cosmetics such as lipstick lanolin, a mixture of waxes obtained from wool, is used in hand and facial lotions to aid retention of water, softening the skin Waxes Cell Membrane separates the contents of a cell from the external fluids semipermeable so that nutrients can enter the cell and waste products can leave main components of a cell membrane are the glycerophospholipids two layers of glycerophospholipids are arranged with their hydrophobic tails in the center and their hydrophilic heads at the outer and inner layers of the membrane lipid bilayer outer layer of glycerophospholipids is in contact with the external fluids inner layer is in contact with the internal contents of the cell Cell Membrane glycerophospholipids in the lipid bilayer contain unsaturated fatty acids do not fit closely together lipid bilayer is not a rigid, fixed structure, but one that is dynamic and fluid-like proteins, carbohydrates, and cholesterol molecules are present fluid mosaic model of membrane Cell Membrane Cell Membrane peripheral proteins emerge on just one of the surfaces, outer or inner integral proteins extend through the entire lipid bilayer and appear on both surfaces of the membrane carbohydrate responsible for cell recognition and communication cholesterol reduce the flexibility of the lipid bilayer and add strength to the cell membrane Cell Membrane