 Lipids have three important roles in human biochemistry  Energy is stored within fat cells  Help to separate aqueous solutions in cell membranes  They serve as chemical messengers

 Animals and humans store energy in fat cells  When fats are burned, they produce twice as much energy as carbohydrates produced

 Lipids are not water soluble due to the polar groups being much smaller then the nonpolar parts  This makes them perfect for separating compartments within cells

 Serve as chemical messengers  Steroid hormones are primary messengers  Prostaglandins and thromboxanes are examples of secondary messengers who activate the hormones responses

 Four lipid groups  Simple lipids(fats and waxes)  Complex lipids  Steroids  Prostaglandins, thromboxanes, and leukotrienes

 Triesters of glycerol of long-chain carboxylic acids  Alcohol of triglycerides are always glycerol  Acid component may be any number of fatty acids  Animal fats and plant oils

 Unbranched carboxylic acids  Chains from carbons  Even number carbon chains  One functional group (OH – hydroxyl)  Cis-isomer predominates

 Triglycerides  Most common lipid material  Mono & triglycerides are not infrequent

 Caused by long hydrocarbon  Ester groups are buried in non-polar environment  Insoluble in water

 Fats are usually solid at room temp  Liquids are oils (plant and fish)

 Solid animal fats contain saturated fatty acids  Some have unsaturated  Vegetable oils contain high amounts of unsaturated fatty acids  Some have saturated  Colorless, odorless, tasteless,  Flavor is caused by other dissolved substances

 Vegetable Oil  High amounts of unsaturated fatty acids  Coconut Oil  Small amount of unsaturated fatty acids  Rich in low-molecular-weight fatty acids  (chiefly lauric acid)

 Unsaturated fatty acids  Linoleic and linolenic aicds  Body cannot synthesize these acids  Obtained from our diet

 Oils with an average of more than one double bound per fatty acid chain

 Reduce C-C double bonds to single bonds  Treated with hydrogen and a catalyst  Hydrogenate all double bonds, a fat with no double bonds may be too solid  Margarine – partial hydrogenation of veg oils  Contains more unsaturation than fully hydrogenated shortenings  Source of trans fatty acids

 Glycerides are subjected to hydrolysis  Carried out by acids or bases  Base-promoted hydrolysis of fats and oils producing glycerol and a mixture of fatty acid salts  Soaps