Lipids

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

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.

Triglycerides (Neutral Lipids) Formed by esterification (condensation reaction between 3 fatty acids and glycerol) H C O Glycerol

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

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

Esterification H C O C O H Fatty acid Glycerol

Esterification H C O C O H Fatty acid Glycerol

Esterification C H O C O H H O Fatty acid Glycerol

Esterification C H O C O H Ester bond H O water

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

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

Classification of Lipids Simple lipids Compound lipids (Complex) Derived lipids

Simple lipids A) Natural 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

Simple lipids B) Waxes 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 Myricyl alcohol and palmitic acid.

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

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

Derived lipids Hormones Steroids

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.

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.