1. Lipids

2. Lipids  Made up of C, H and O  Can exist as fats, oils and waxes  They are insoluble in water  They are a good source of energy  (9 k cal / g)  They are poor conductors of heat  Most fats & oils are triglycerides

3. Lipids  Biomolecules that contain fatty acids or a steroid nucleus.  Soluble in organic solvents, but not in water.  Named for the Greek word lipos, which means “fat.”  Extracted from cells using organic solvents.

4. Triglycerides  Formed by esterification (condensation reaction between 3 fatty acids and glycerol) Glycerol H C H C C H H H H O O O H H

5. Fatty acids  Carboxyl group (-COOH)  attached to a long non-polar hydrocarbon chain (hydrophobic) H H C H H C H H C H C O O H C H H C H H C H H C H H A saturated fatty acid (no double bonds)

6. A polyunsaturated fatty acid C O O H C H H C H H C H H C H C H H C H H C H H A monounsaturated fatty acid HH C O O H C H H CC CC H C H H C H H HH

7. Esterification C O O H C H H C H H C H H C H H Glycerol Fatty acid H C H C C H H H H O O O H H

8. Esterification C O O H C H H C H H C H H C H H Glycerol Fatty acid H C H C C H H H H O O O H H

9. Esterification C O H C H H C H H C H H C H Glycerol Fatty acid C H C C H H H H O O O H H H O H

10. Esterification C O H C H H C H H C H H C H C H C C H H H H O O O H H H O H Ester bond water

11.  This happens three times to form a triglyceride glycerol fatty acids Esterification

12. Phospholipids One fatty acid can be replaced by a polar phosphate group glycerol Hydrophobic fatty acids hydrophilic phosphate

13. Classification of Lipids  Simple lipids  Compound lipids (Complex)  Derived lipids

14. Simple lipids  The alcohol is glycerol  Oil (liquid at room temperature)  Fat (solid at room temperature)  Natural lipids need 3 F.As. and one molecule of glycerol to form triglycerides + 3 H 2 O A) Natural Lipids

15. Simple lipids  Most natural waxes are esters derived from a fatty acid and a long-chain alcohol  Main biological function of waxes: water barrier  Bee waxes are formed by honey bee and formed from merioyl alcohol and palmitic acid. B) Waxes

16. Waxes  Most natural waxes are esters derived from a fatty acid and a long-chain alcohol Main biological function of waxes: water barrier Myricyl cerotate Present in beeswax Cerotic acid A fatty acid remove H 2 O Leaves Wax minimizes water evaporation Myricyl alcohol Long chain alcohol Feathers Wax minimizes wetting

17. Compound lipids  F.A + alcohol + other group  Phospholipids (contain phosphate group)  Glycolipids (contain carbohydrates)  Lipoproteins (contain proteins)

18. Derived lipids  Hormones  Steroids

19.  Non-polar lipids (fats) are the principal molecules for energy storage.  Polar lipids (nitrogen and phosphorus containing) are components of biological membranes.  The steroid (class of lipids) (cholesterol) is found in biological membranes and used as a precursor for many hormones, bile and vitamin D  Miscellaneous lipids present only in minor quantities in the cell are involved as light-absorbing pigments (β-carotene, retinal), enzyme cofactors (vitamin K), signal molecules (prostaglandins), and electron carries. Diversity in structure leads to a diversity in biological function

20.  Used as a fuel reserve (when needed)  Provide body with essential fatty acids  Fats under skin (subcutaneous) are used as insulator and protecting and maintaining the body temperature.  Fats provide the protection and fixation of internal organs.  Lipoproteins enter in the formation of cell wall, muscles, mitochondria and microsomes.