Lipids

• Lipids are insoluble in water.
• fatty acid oxidation is highly exergonic.
• Fatty acids with unbranched chains and no double bonds are said to be fully saturated.
• Polyunsaturated fatty acids usually have their double bonds between C-12 and C-15.
• Monounsaturated fatty acids usually have their double bonds between C-9 and C-10.
• In most unsaturated fatty acids the double bonds are usually in the cis configuration.
• Trans fatty acids are produced by fermentation in the rumen of dairy animals and are obtained in dairy products or meat.
• Melting points are strongly influenced by the length and degree of unsaturation of the hydrocarbon chain.
• The nonpolar hydrocarbon chain accounts for the poor solubility of fatty acids in water.
• The carboxylic acid group in fatty acids is polar, contributing a slight solubility in short fatty acid chains.
• At room temp saturated fatty acids are waxy, while unsaturated fatty acids are oily liquids.
• The difference in melting points of fatty acids is due to different degrees of packing.
• In fully saturated fatty acids, the free rotation around carbon bonds gives the hydrocarbon chain flexibility.
• The most stable conformation of saturated compounds is the fully extended form.
• Unsaturated fatty acids have weaker interactions due to the double bonds creating kinks in the hydrocarbon chain.
• Unsaturated fatty acids have lower melting points.
• Free fatty acids circulate in the blood bounded to serum albumin.
• Free fatty acids are present in the blood usually in the form of esters or amides.
• The simplest lipids constructed from fatty acids is TAG.
• TAG structure: 3 fatty acids, linked through esters to a single glycerol.
• TAG is nonpolar, essentially insoluble in water.
• Adipocytes store large amounts of TAG as fat droplets.
• Lipases catalyze the hydrolysis of stored TAG. Which releases fatty acids for export to sites that need them.
• Oxidation of TAG yields more energy than oxidation of carbohydrates.
• TAG provides insulation against low temperatures.
• The unpleasant taste and smell associated with rancidity results from the oxidative cleavage of double bonds in unsaturated fatty acids.
• Converting cis double bonds to single bonds increases the melting point of oils.
• LDL is bad cholesterol.
• Waxes usually have a higher melting point than TAGs.