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

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

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

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

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

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

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

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

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

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 H2O 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. Cerotic acid A fatty acid remove H2O Myricyl alcohol Long chain alcohol Myricylcerotate Present in beeswax Feathers Wax minimizes wetting Leaves Wax minimizes water evaporation Waxes • Most natural waxes are esters derived from a fatty acid and a long-chain alcohol • Main biological function of waxes: water barrier

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

18. Derived lipids • Hormones • Steroids

19. Diversity in structure leads to a diversity in biological function • 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.

20. Diversity in structure leads to a diversity in biological function • 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.