The Chemistry of Lipids PDF

THE CHEMISTRY OF LIPIDS Debbie Ann S. Tuazon, MAE-Chem Faculty, College of Science H C O N S P Hydrocarbons Carbohydrates & Lipids Amino acids & proteins More amino acids & proteins...

THE CHEMISTRY OF LIPIDS Debbie Ann S. Tuazon, MAE-Chem Faculty, College of Science H C O N S P Hydrocarbons Carbohydrates & Lipids Amino acids & proteins More amino acids & proteins Nucleic acids, RNA, & DNA Single atoms of iron, copper, magnesium for some proteins ORGANIC BUILDING BLOCKS  LIPIDS  A heterogeneous class of naturally occurring organic compounds classified together on the basis of common solubility properties. Insoluble in water, but soluble in organic solvents including diethyl ether, dichloromethane, and acetone. 3  CLASSIFICATION OF LIPIDS A. Based on its Function Storage. They store energy and protect and insulate internal organs. In human bodies they are stored as fat cells. Membrane Components. Because they are not soluble in water, a major function of lipids is to build the cell membranes that separate the internal contents of cells from the surrounding aqueous environment. Messenger. They are found in nerve fibers and hormones as steroids, which act as chemical messengers.  CLASSIFICATION OF LIPIDS B. Based on Its Structure Simple Lipids. these are esters of fatty acids with various alcohols. e.g Fats and oils, waxes Complex Lipids. - esters of fatty acids containing groups in addition to an alcohol and a fatty acid. e.g Phospholipids, Glycolipids, Lipoproteins and other complex lipids : lipids such as sulfolipids, and amino lipids. Derived Lipids. these include eicosanoids, steroids, fatty aldehydes, and ketone bodies, lipid-soluble vitamins and hormones.  FATTY ACIDS (FA) are long chain carboxylic acids 12-20 hydrocarbon LINEAR chains (most even #) are often complexed in triacylglycerols (TAGs) By nature, fatty acids are AMPHIPATHIC – have both hydrophilic and hydrophobic parts  FATTY ACIDS (FA) TWO TYPES of FAs Saturated. hydrocarbon has NO double bonds Unsaturated. Hydrocarbon chain has ONE or MORE DOUBLE BONDS Double bonds are “cis” configuration  FATTY ACIDS (FA) Lipids can contain many different fatty acids  Fatty acid chain length and degree of unsaturation affect Melting point and Fluidity of lipids SATURATED FATTY ACIDS Pack close together Less fluid (FAs can’t move as freely) Higher melting temperature because it takes more energy to break interactions Likely to be solids at room temperature UNSATURATED FATTY ACIDS Do NOT pack as closely More fluid than saturated Lower melting temperature than saturated Likely to be liquid at room temperature  FATTY ACIDS (FA) NOMENCLATURE OF FA’s (DELTA NOMENCLATURE) Referred to as a system of numbers # of carbons: # double bonds Δx, y, z (position of double bonds) e.g Oleic Acid Linoleic Acid 18:2 9,12  FATTY ACIDS (FA) NOMENCLATURE OF FA’s ( OMEGA NOMENCLATURE) Carbons are counted from the methyl (omega) end instead of the carboxylic acid end The ω symbol is used instead of the delta symbol Number of carbons in the FA Number of double bonds Number of carbons from the methyl end (aka Omega end) to the first carbon in the double bond closest to the methyl end  FATTY ACIDS (FA) Essential Fatty Acids & Eicosanoids  The two essential fatty acids are linoleic acid (omega-6) and alpha-linolenic (omega-3)acid. Linoleic acid - 18:2 ω 6 Alpha-Linolenic acid - 18:3 (ω 3)  FATTY ACIDS (FA) NOMENCLATURE OF FA’s (COMMON NAMES)  FATTY ACIDS (FA) Fatty acids are practically all unbranched carboxylic acids. They range in size from about 10 to 20 carbons.  They contain an even number of carbon atoms because the body builds these acids entirely from acetate units. They have no other functional groups, except that some do have double bonds. In most fatty acids that have double bonds, the cis isomers predominate. LEARNING CHECK FATTY ACIDS (FA) Write abbreviated symbols of the following FAs 1.Stearic Acid 2. Docosahexaenoic Acid (DHA)  SIMPLE LIPIDS FATS AND OIL (TRIACYLGYLCEROLS/TAGS)  are triesters of glycerol (an alcohol) and fatty acids (long chain carboxylic acids). They are generally formed by a dehydration reaction. They are hydrolyzed into 3 fatty acids and 1 glycerol.  SIMPLE LIPIDS - TAGS FATS OILS  solid at room temperature  usually liquid at room  e.g fats in meat, whole temperature. milk, butter, and cheese.  come from plant sources.  Most fats come from  e.g. Olive oil and peanut oil are animal sources monounsaturated (one double  Animal fats usually contain bond C=C). more saturated fatty acids  Oils from corn, cottonseed, than do vegetable oils safflower, and sunflower are polyunsaturated (two or more double bond C=C).  SIMPLE LIPIDS - TAGS The physical properties of triglycerides depend on the fatty acid components. Melting points of fatty acids increases as the number of carbons in the hydrocarbon chains increases and as the number of double bonds decreases. Triglycerides rich in unsaturated fatty acids are generally liquid at room temperature and are called oils Triglycerides rich in saturated fatty acids are generally semisolids or solids at room temperature and are called fats. 17 SIMPLE LIPIDS-TAGS SIMPLE LIPIDS - TAGS SIMPLE LIPIDS - TAGS  SIMPLE LIPIDS - TAGS CHEMICAL PROPERTIES OF TRIACYLGLYCEROLS: Hydrogenation  hydrogenation of unsaturated fats converts carbon-carbon double bonds to single bonds.  The hydrogen gas bubbled through the heated oil the presence of a nickel catalyst (or another transition metal). SIMPLE LIPIDS - TAGS  SIMPLE LIPIDS - TAGS Hardening: The reduction of some or all of the carbon-carbon double bonds of an unsaturated triglyceride using H2/transition metal catalyst, which converts a liquid triglyceride to a semisolid. In practice, the degree of hardening is carefully controlled to produce fats of a desired consistency. The resulting fats are sold for kitchen use (Crisco, Spry, Dexo, and others). Margarine and other butter substitutes are produced by partial hydrogenation of polyunsaturated oils derived from corn, cottonseed, peanut, and soybean oils. The hardening process is the source of trans fatty acids 24  SIMPLE LIPIDS - TAGS CHEMICAL PROPERTIES OF TRIACYLGLYCEROLS: Hydrogenation Note:  Most of the time the liquid oil hydrogenate to produce solid oil.  This process has two advantages: increasing the period of consumption and transporting easer the solid product. In commercial hydrogenation, the addition of hydrogen is stopped before all the double bonds in oil become completely saturated.  As a result, we can obtain a soft and semisolid product instead of a brittle product. This control of hydrogenation gives the various products such as soft margarines, solid stick margarine, and solid shortenings.  SIMPLE LIPIDS - TAGS CHEMICAL PROPERTIES OF TRIACYLGLYCEROLS: Hydrolysis  triacylglycerol are hydrolyzed (split by water) in the presence of strong acids or digestive enzymes called lipases.  The products of hydrolysis of the ester bonds are glycerol and three fatty acids.  SIMPLE LIPIDS - TAGS CHEMICAL PROPERTIES OF TRIACYLGLYCEROLS: Hydrolysis  SIMPLE LIPIDS - TAGS CHEMICAL PROPERTIES OF TRIACYLGLYCEROLS: Hydrolysis  SIMPLE LIPIDS - TAGS CHEMICAL PROPERTIES OF TRIACYLGLYCEROLS: Saponification  when a fat is heated with a strong base such as sodium hydroxide, saponification of the fat gives glycerol and the sodium salts of the fatty acids, which are soaps. KOH produces a softer, liquid soap. Oils that are polyunsaturated produce softer soaps. Names like “coconut” or “avocado shampoo” tell you the sources of the oil used in the reaction.  SIMPLE LIPIDS - TAGS CHEMICAL PROPERTIES OF TRIACYLGLYCEROLS: Saponification  SIMPLE LIPIDS - TAGS CHEMICAL PROPERTIES OF TRIACYLGLYCEROLS: Saponification  SIMPLE LIPIDS - TAGS 1. Write the structure and name the TAG’s produce with Glycerol and 1stearic Acid + 2 Palmitic Acids 2. Write the complete reaction (structure) and name the product formed in the hydrolysis of glycerol trioleate. 3.Write the complete reaction (structure) and name the product formed in the saponification process of glycerol trilaurate andNaOH.