2. Lipids - Six functions of lipids: 1. Long term energy storage 2.Protection against heat loss (insulation) 3.Protection against physical shock 4.Protection against water loss 5.Chemical messengers e.g., hormones (steroids) 6.Major component of membranes (phospholipids )

3. Lipids Two forms: 1.Fats (Solid at room temperature, animal origin) 2.Oils (Liquid at room temperature, plant origin) e.g., 1- Triglycerides 2- Oils 3- Waxes 4- Phospholipids 5- Steroid hormones

4. Fats and oils formed from One glycerol molecule Three fatty acid molecules

5. - Condensation synthesis and hydrolysis of a fat molecule. Fatty acids can be saturated (no double bonds between carbon atoms) or unsaturated (have double bonds between carbon atoms). When a fat molecule forms, three fatty acids combine with one glycerol, and three water molecules are produced. + + 3 H 2 O

6. Triglycerides Triglycerides: composed of 1 glycerol and 3 fatty acids. H H-C----O H glycerol O C-CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 3 = fatty acids O C-CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 3 = O C-CH 2 -CH 2 -CH 2 -CH =CH-CH 2 -CH 2 -CH 2 -CH 2 -CH 3 =

7. Emulsification Emulsifiers can cause fats to mix with water. They contain molecules with a nonpolar end and a polar end. The molecules position (surround) themselves about an oil droplet so that their polar ends project. Now the droplet disperses in water, which means that emulsification has occurred. + emulsifierfat emulsion

8. - Emulsification takes place when dirty clothes are washed with soaps or detergents. - Also, prior to the digestion of fatty foods, fats are emulsified by bile. - The gall bladder stores bile for emulsifying fats prior to the digestive process.

9. Saturated and Unsaturated Fatty Acids Fatty acids are long chains of hydrocarbons ending in -COOH (from 16 :18 C per molecule) Fatty acids may be: 1- Saturated fatty acids contain only single covalent bonds between the carbon atoms (no double bonds) solid at room temp., e.g., lard and butter 2- Unsaturated fatty acids contain one or more double bonds in the carbon chain liquid at room temp., e.g., vegetable oils

10. Phospholipids -Essentially, they are constructed like fats, except that in place of the third fatty acid, there is a phosphate group or a grouping that contains both phosphate and nitrogen. -Phospholipids molecules are not electrically neutral, as are fats, because the phosphate containing groups are ionized. -They form the so-called hydrophilic head of the molecule, while the rest of the molecule becomes the hydrophobic tails. -The hydrophilic heads face outward toward watery solutions and the tails form the hydrophobic interior.

11. Phospholipids Has a phosphate group “Tail” is hydrophobic, “head” is hydrophilic Phospholipids assemble spontaneously into many convenient shapes when placed in water. Pepper & Soap Activity

12. The bilipid layer is the basis for all cellular membranes.

13. Steroids - Steroids are lipids that have different structure from those of fats. - Steroid molecules have a backbone of four fused carbon rings. - Each one differs primarily by the functional groups attached to rings. Cholesterol

14. Dr. Essam Ibrahim