Chapter 13 Lipids Tiara Bartol and Brant Houghton

13.1 What are lipids? Family of substances that are insoluble in water but soluble in nonpolar solvents and solvents of low polarity Family of substances that are insoluble in water but soluble in nonpolar solvents and solvents of low polarity Defined in terms of properties Defined in terms of properties

Classification of Function 3 roles 3 roles Storage energy within fat cells Storage energy within fat cells Part of membranes that separate compartments of aqueous solutions Part of membranes that separate compartments of aqueous solutions Serve as chemical messengers Serve as chemical messengers Storage Storage Important in animals Important in animals Use fats for storage Use fats for storage Glycogen Glycogen Greater amount of energy Greater amount of energy 9 Kcal/g 9 Kcal/g

Membrane Component Membrane Component Lipids lack water solubility Lipids lack water solubility The body needs insoluble compounds for membranes that separate aqueous solutions The body needs insoluble compounds for membranes that separate aqueous solutions Derives from smaller polar groups than alkane like portions Derives from smaller polar groups than alkane like portions Nonpolar provide hydrophobic part Nonpolar provide hydrophobic part

Messengers Messengers Primary messenger delivers signals from one part of body to another Primary messenger delivers signals from one part of body to another Steroid hormones Steroid hormones Secondary messenger meditates hormonal response Secondary messenger meditates hormonal response prostaglandins and thromboxanes prostaglandins and thromboxanes

Classification by Structure 4 groups Simple lipids Simple lipids Fats and waxes Fats and waxes Complex lipids Complex lipids Steroids Steroids Prostaglandins, thromboxanes, and leukotrienes Prostaglandins, thromboxanes, and leukotrienes

13.2 What are structures of Triglycerides? Triglyceride Triglyceride Animal fats and plant oils Animal fats and plant oils Triesters of glycerol and long chain carboxylic acids called fatty acids Triesters of glycerol and long chain carboxylic acids called fatty acids

Even number of acids Even number of acids Aka triacylglycerols Aka triacylglycerols 3 groups of glycerol are esterified 3 groups of glycerol are esterified Complex mixtures Complex mixtures Most cases 2 or 3 different fatty acids are present Most cases 2 or 3 different fatty acids are present Hydrophobic character is caused by long chain Hydrophobic character is caused by long chain Esters are buried in nonpolar environment which makes them insoluble Esters are buried in nonpolar environment which makes them insoluble

Fatty acids Fatty acids Practically all unbranched carboxylic acids Practically all unbranched carboxylic acids 10 to 20 carbosn 10 to 20 carbosn Even # of carbons Even # of carbons Cis isomer predominates Cis isomer predominates Mono and diglycerides Mono and diglycerides Not infrequent Not infrequent Latter two sides Latter two sides 1 or 2 OH groups are esterified 1 or 2 OH groups are esterified

13.3 What are properties of Triglycerides? Fats Fats A mixture of triglycerides containing a high proportion of long chain, saturated fatty acids A mixture of triglycerides containing a high proportion of long chain, saturated fatty acids Oils Oils A mixture of triglycerides containing a high proportion of long chain, unsaturated fatty acids or short chain, saturated fatty acids A mixture of triglycerides containing a high proportion of long chain, unsaturated fatty acids or short chain, saturated fatty acids

Physical State Physical State Fats are generally solids at room temperature Fats are generally solids at room temperature Fats from plants and fish are liquids Fats from plants and fish are liquids Liquid fats are oils Liquid fats are oils Solid fats are mainly saturated fatty acids Solid fats are mainly saturated fatty acids Vegetable oil has high amounts of unsaturated fatty acids Vegetable oil has high amounts of unsaturated fatty acids Essential fatty acids Essential fatty acids The body needs but can’t synthesize The body needs but can’t synthesize

Most oils contain large amounts of unsaturated fatty acids Most oils contain large amounts of unsaturated fatty acids Coconut oil has a small amount Coconut oil has a small amount Polyunsaturated fatty acids have more than one double bond Polyunsaturated fatty acids have more than one double bond Pure fats and oils are colorless, odorless, and tasteless Pure fats and oils are colorless, odorless, and tasteless To gain taste substances must be added To gain taste substances must be added

Hydrogenation Hydrogenation Easy to convert unsaturated liquids and oils to solids Easy to convert unsaturated liquids and oils to solids Don’t hydrogenate all double bonds Don’t hydrogenate all double bonds It will become too solid It will become too solid This is the source of trans fatty acids This is the source of trans fatty acids

Saponification Base promoted hydrolysis of fats and oils Produce glycerol and a mixture of fatty acids called soap It is the oldest known chemical reaction