Chapter 15 Structure and bonding in food molecules 15.5 - Fats and oils Parnika Mahajan · fats and oils are a major source of energy in our diet · fats are used by animals to store chemical energy · fats and oils belong to the class of biological molecules called lipids Triglycerides · fats and oils contain large non-polar molecules known as triglycerides · fats and oils have very similar chemical structures and are distinguished simply on the basis of their physical state at room temperature o at room temperature, fats are solids and oils are liquids · triglycerides (which are non-polar) are unable to form hydrogen bonds with water so fats are insoluble in water and oils are immiscible (cannot mix) with water · non-polar organic compounds such as vitamins can dissolve in triglycerides General structure of a fatty acid and glycerol · triglycerides are produced from a condensation reaction between glycerol and three fatty acid molecules H 1 H-C-OH 1 H-C-OH 1 H-C-OH 1 H glycerol 0=0 HO-C-CH,CH,CH,CH,CH,CH,CH,CH,CH,CH,CH,CH,CH,CH,CH,CH?CH, fatty acid FIGURE 15.5.2 A glycerol molecule and a fatty acid molecule. · glycerol (propane-1,2,3-triol) is a relatively small molecule with three hydroxyl functional groups (-OH) · fatty acids have a carboxyl functional group (-COOH) attached to a long unbranched hydrocarbon chain Saturated Fatty Acid OH HH HH HH HH HH T HO-C-C-C-C-C-C-C-C-C-C-C-C-H HH HH HH HH HH H Unsaturated Fatty Acid OHHHHH HO-C-C-C-C-C- C HH HH /HH C-C-H H !! 1
Chapter 15 Structure and bonding in food molecules 15.5 - Fats and oils Condensation reactions to form triglycerides Parnika Mahajan H I- 0 H-C-OH HO-CM O H-C-OH HO-CV O head H 3 hydrocarbon tails O H-C-0-CW O condensation I 3H20 O H-C - 1 OH HO-C H H-C -0- CW H glycerol + 3 fatty acid molecules with hydrocarbon tails triglyceride molecule fatty acid fatty acid or, more simply glycerol fatty acid condensation glycerol fatty acid fatty acid 3H20 fatty acid Key glycerol fatty acid ester bond · a condensation reaction can occur between a molecule that contains a carboxyl group (-COOH) and a molecule that contains a hydroxyl group (-OH) to form an ester functional group (-coo-) · a triglyceride is produced by a condensation reaction that involves the carboxyl group of a fatty acid and a hydroxyl group of glycerol, forming an ester link H,O is formed H 4 0 H-C-OH HO (CH2)1CH, H | H-C- ester link 0 (CH2)16CH3 0 H-C-OH HO- 00=00=0 0 0 C - (CH2),CH, H-C-OH HO - (CH2)1CH3 0-C-(CH2),CH, + 3H,O H-C | 0 H-C-0-C-(CH2)1CH3 H glycerol fatty acids H triglyceride FIGURE 15.5.3 Equation showing a reaction between glycerol and fatty acids to produce a triglyceride and water. NOTE: the hydrocarbon chains of the fatty acids can differ in length 2
Parnika Mahajan Chapter 15 Structure and bonding in food molecules 15.5 - Fats and oils Saturated and unsaturated fatty acids . fats are classified on the basis of the structural features of the hydrocarbon chains of their fatty acid components