Chapter 13.1 – 13.3 Olivia Kratzer and Kippy Palko

Three major roles in biochemistry 1)They store energy within fat cells. 2)They are parts of membranes that separate compartments of aqueous solutions from each other. 3)They serve as chemical messengers.

 Storage of energy In plants  Starch In animals  Fats  The burning of fat produces much more energy than carbohydrates

 The body is heavily based on water so lipids that aren’t water soluble are important  The body needs insoluble compounds for the membranes that separate the compartments that contain aqueous solutions  Hydrophobic Water repellent

 Lipids are chemical messengers Primary messengers  Deliver signals from one part of the body to another part Secondary messengers  Mediate the hormonal response

 Classified as Simple lipids  Fats  Waxes Complex lipids Steroids Prostaglandins, thromboxanes, and leukotrienes

 Triglycerides Triesters of glycol and long-chain carboxylic acids called fatty acids Fatty Acids have things in common  Practically all unbranched carboxylic acids  Range in size from 10 to 20 carbons  Have an even number of carbons  No functional groups other than –COOH  Most have double bonds with a predominate –cis isomer

 Triglycerides All 3 groups of glycerol are esterfied Most common lipid materials Some molecules have 3 of the same fatty acids but its more common to have 2 or 3 different fatty acids

 Triglycerides Properties  Hydrophobic  Polar, but surrounded by nonpolar environment  Insoluble in water

 Properties of Triglycerides Physical state  Fats from animals are solids at room temperature and fats from plants and fish are usually liquids  Liquid fats are often called oils. Oils often have unsaturated fatty acids  Solid fats are mostly saturated fatty acids  Some unsaturated fatty acids are essential fatty acids because the body cannot synthesize them from precursors  Pure fats and oils are colorless, odorless, and tasteless  Tastes, odors, and colors are caused by small amounts of other substances dissolved in the fat or oil.

 Properties of Triglycerides Hydrogenation  It is not hard to convert unsaturated liquid oils to solids.  Hydrogenation is used on a large scale for the production of shortening, like Crisco.  Producers of this product have to be careful not to hydrogenate all of the double bonds because it would be too solid.

 Properties of Triglycerides Saponification  These are subject to hydrolosis that can be carried out by either an acid or a base.  Bases are predominantly used.  Saponification is the base-promoted hydrolosis of fats and oils to make soaps.