Lipid Def: compounds which are relatively insoluble in water, but freely soluble in non polar organic solvents like benzene, ether, chloforom etc.
Function 1.Storage form of energy 2.Structure component of biomembranes 3.Insolution 4.Shape and contour of body 5.Protect internal organ 6.Metabolic regulator 7.Electric insulator in neurons 8.Help in absorbtion of fat soluble vitamins 9.Taste and palatability
6 Types of Lipids Lipids with fatty acids Waxes Fats and oils (trigycerides) Phospholipids Sphingolipids Lipids without fatty acids Steroids
7 Fatty Acids Long-chain carboxylic acids Insoluble in water Typically 12-18 carbon atoms (even number) Some contain double bonds corn oil contains 86% unsaturated fatty acids and 14% saturated fatty acids
8 Saturated and Unsaturated Fatty Acids Saturated = C–C bonds Unsaturated = one or more C=C bonds
9 Structures Saturated fatty acids Fit closely in regular pattern Unsaturated fatty acids Cis double bonds
10 Properties of Saturated Fatty Acids Contain only single C–C bonds Closely packed Strong attractions between chains High melting points Solids at room temperature
11 Properties of Unsaturated Fatty Acids Contain one or more double C=C bonds Nonlinear chains do not allow molecules to pack closely Few interactions between chains Low melting points Liquids at room temperature
12 Learning Check L1 How would the melting point of stearic acid compare to the melting points of oleic acid and linoleic acid? Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain. stearic acid (18 C) saturated oleic acid (18 C) one double bond linoleic acid (18 C) two double bonds
13 Solution L1 Stearic acid is saturated and would have a higher melting point than the unsaturated fatty acids. Because linoleic has two double bonds, it would have a lower mp than oleic acid, which has one double bond. stearic acid mp 69°C oleic acid mp 13°C linoleic acid mp -17°C
14 Fats and Oils Formed from glycerol and fatty acids
15 Triglycerides (triacylglcerols) Esters of glycerol and fatty acids
16 Learning Check L2 What are the fatty acids in the following triglyceride?
17 Solutions L2 What are the fatty acids in the following triglyceride? Stearic acid Oleic acid Myristic acid
18 Properties of Triglycerides Hydrogenation Unsaturated compounds react with H 2 Ni or Pt catalyst C=C bonds C–Cbonds Hydrolysis Split by water and acid or enzyme catalyst Produce glycerol and 3 fatty acids