skibidi-chem.pdf

LIPIDS an organic compound found in living organisms that is insoluble (or only sparingly soluble) in water but soluble in nonpolar organic solvents. When a biochemical material (human, animal, or plant tissue) is homogenized in a blender and mixed with a nonpolar organic solvent, the substances t...

LIPIDS an organic compound found in living organisms that is insoluble (or only sparingly soluble) in water but soluble in nonpolar organic solvents. When a biochemical material (human, animal, or plant tissue) is homogenized in a blender and mixed with a nonpolar organic solvent, the substances that dissolve in the solvent are the lipids. LIPIDS known as fats provide a major way of storing chemical energy and carbon atoms in the body. FATS also surround and insulate vital body organs, providing protection from mechanical shock and preventing excessive loss of heat energy. Phospholipids, glycolipids, and cholesterol (a lipid) are the basic components of cell membranes. Several cholesterol derivatives function as chemical messengers (hormones) within the body. Based on biochemical function, lipids are divided into five categories: 1. Energy-storage lipids (triacylglycerols) 2. Membrane lipids (phospholipids, sphingoglycolipids, and cholesterol) 3. Emulsification lipids (bile acids) 4. Messenger lipids (steroid hormones and eicosanoids)  5. Protective-coating lipids TYPES OF FATTY ACIDS; (biological waxes) A SATURATED FATTY ACID (SFAs) Based upon whether or not fatty acid with a carbon chain in saponification occurs when a lipid is which all carbon– carbon bonds are placed in basic aqueous solution, lipids single bonds. are divided into two categories: 1. Saponifiable lipids (triacylglycerols, phospholipids, sphingoglycolipids, and biological waxes) 2. Nonsaponifiable lipids (cholesterol, steroid hormones, bile acids, and eicosanoids) Note: Saponifiable lipids are converted into smaller molecules when TYPES OF FATTY ACIDS hydrolysis occurs. Nonsaponifiable A MONOUNSATURATED FATTY lipids cannot be broken up into smaller ACID (MUFAs) units since they do not react with water. fatty acid with a carbon chain in FATTY ACIDS which one carbon–carbon double bond A fatty acid is a naturally occurring is present. In biochemically important monocarboxylic acid. Because of the MUFAs, the configuration about the pathway by which they are double bond is nearly always cis. biosynthesized, fatty acids nearly always contain an even number of carbon atoms and have a carbon chain that is unbranched. In terms of carbon chain length, fatty acids are characterized as long-chain fatty acids (C12 to C26), medium-chain fatty acids (C8 and C10), or short-chain A POLYUNSATURATED FATTY fatty acids (C4 and C6). ACID (PUFAs) Fatty acids are rarely found free in fatty acid with a carbon chain in nature but rather occur as part of the which two or more carbon–carbon structure of more complex lipid double bonds are present. Up to six molecules. double bonds are found in biochemically important PUFAs. UNSATURATED FATTY ACIDS Several different “families” of AND DOUBLE-BOND POSITION unsaturated fatty acids exist. These family relationships become apparent A numerically based shorthand when double-bond position is specified system exists for specifying key relative to the methyl (noncarboxyl) structural parameters for fatty acids. In end of the fatty acid carbon chain. this system, two numbers separated by a colon are used to specify the number Double bond positioning determined of carbon atoms and the number of in this manner is denoted by using the carbon–carbon double bonds present. Greek lowercase letter omega (Ѡ). EXAMPLE: An omega-3 fatty acid is an unsaturated fatty acid with its endmost 18: 0 double bond three carbon atoms away 18:2 from its methyl end. To specify double-bond positioning within the carbon chain of an unsaturated fatty acid, the preceding An omega-6 fatty acid is an notation is expanded by adding the unsaturated fatty acid with its endmost Greek capital letter delta (δ) followed double bond six carbon atoms away by one or more superscript numbers. from its methyl end. MUFAs are usually δ9 acids, and the first two additional double bonds in PUFAs are generally at the δ12 and δ15 locations. PHYSICAL PROPERTIES: A trend of particular significance is that saturated fatty acids have higher FATTY ACIDS melting points than unsaturated fatty Water solubility for fatty acids is a acids with the same number of carbon direct function of carbon chain length; atoms. The greater the degree of solubility decreases as carbon chain unsaturation, the greater the reduction length increases. in melting points. Melting points for fatty acids are strongly influenced by both carbon chain length and degree of unsaturation (number of double bonds present). As carbon chain length increases, melting point increases.  The double bonds in unsaturated fatty acids, which generally have the cis configuration, produce “bends” in the carbon chains of these molecules. These “bends” prevent unsaturated fatty acids from packing together as tightly as saturated fatty acids. The greater the number of double bonds, the less efficient the packing. As a result, unsaturated fatty acids always have fewer intermolecular attractions, and therefore lower melting points, than their saturated PHYSICAL PROPERTIES OF counterparts. FATTY ACIDS The decreasing melting point associated with increasing degree of unsaturation in fatty acids is explained by decreased molecular attractions between carbon chains. ENERGY STORAGE LIPIDS Within the name triacylglycerol is the term acyl. An acyl group is the portion TRIACYLGLYCEROLS of a carboxylic acid that remains after TRIACYLGLYCEROL the -OH group is removed from the carboxyl carbon atom. a lipid formed by esterification of three fatty acids to a glycerol molecule.  LIPIDS known as triacylglycerols also function within the body as energy-storage materials. Rather than being widespread, triacylglycerols are concentrated primarily in special cells (adipocytes) that are nearly filled with the material. Adipose tissue containing these cells is found in various parts of the body: under the skin, in the SIMPLE TRIACYLGLYCEROL abdominal cavity, in the mammary glands, and around various organs. Triacylglycerols are much more efficient at storing energy than is glycogen because large quantities of them can be packed into a very small volume. These energy-storage lipids are the most abundant type of lipid present in the human body. MIXED TRIACYLGLYCEROL ENERGY STORAGE LIPIDS TRIACYLGLYCEROLS: FATS AND OILS FATS Representative triacylglycerols from (a) a fat and (b) an oil is a triacylglycerol mixture that is a solid or a semi-solid at room 2. Pure fats and pure oils are colorless, temperature (258C). Generally, fats odorless, and tasteless. are obtained from animal sources. The tastes, odors, and colors OILS associated with dietary plant oils are caused by small amounts of other An oil is a triacylglycerol mixture naturally occurring substances present that is a liquid at room temperature in the plant that have been carried along (258C). Generally, oils are obtained during processing. from plant sources. The presence of these “other” compounds is usually considered desirable. PROPERTIES OF FATS AND OILS 1. Fats are composed largely of triacylglycerols in which saturated fatty acids predominate, although some unsaturated fatty acids are present. Such triacylglycerols can pack closely together because of the “linearity” of their fatty acid chains, thus causing the higher melting points associated with fats. In general, a higher degree of fatty acid Oils contain triacylglycerols with unsaturation is associated with oils than larger amounts of mono- and with fats. A notable exception to this polyunsaturated fatty acids than those generalization is coconut oil, which is in fats. highly saturated. Such triacylglycerols cannot pack as This oil is a liquid not because it tightly together because of “bends” in contains many double bonds within the their fatty acid chains. The result is fatty acids but because it is rich in lower melting points. shorter-chain fatty acids, particularly lauric acid (12:0). DIETARY CONSIDERATIONS -and that polyunsaturated fat can reduce heart disease risk but promote AND TRIACYLGLYCEROLS the risk of certain types of cancers. GOOD FATS vs. BAD FATS Dietary fats high in “good” monounsaturated fatty acids include SALMON olive, avocado, and canola oils. MARGARINE Monounsaturated fatty acids help reduce the stickiness of blood platelets. This helps prevent the formation of blood clots and may also dissolve clots once they form. Most tree nuts and peanuts are good sources of MUFAs. Dietary Considerations “Good Fats” Versus “Bad Fats” OMEGA 3 A dietary fat can be either a “fat” or an “oil.” OMEGA 6 Both the type of dietary fat consumed “Good Fats” Versus “Bad Fats” and the amount of dietary fat consumed Several large studies now confirm are important factors in determining that benefits can be derived from eating human body responses to dietary fat. several servings of fish each week. The Current dietary fat recommendations choice of fish is important, however. are that people limit their total fat Not all fish are equal in omega-3 fatty intake to 30% of total calories—with acid content. up to 15% coming from Cold-water fish, also called fatty fish monounsaturated fat, up to 10% from because of the extra amounts of fat they polyunsaturated fat, and less than 10% have for insulation against the cold, from saturated fats. contain more omega-3 acids than Research studies indicate that leaner, warm-water fi sh. Fatty fish saturated fats are “bad fat,” include albacore tuna, salmon, and monounsaturated fats are “good fat,” mackerel. and polyunsaturated fats can be both Leaner, warm-water fish, which “good fat” and “bad fat.” include cod, catfish, halibut, sole, and Studies indicate that saturated fat can snapper, do not appear to offer as great increase heart disease risk, that a positive effect on heart health as do monounsaturated fat can decrease both their “fatter” counterparts. heart disease and breast cancer risk,-  Wild salmon populations are the primary source for such oil in the US. Fish do not make the omega-3 fatty acids they have within themselves. Rather, they obtain these fatty acids from the algae that they feed on.