Lipids Aims: Must be able to define to the term lipids. Should be able to outline the basic structure of common lipids. Could be able to state the function of lipids and relate their structure to their function.

Lipids Definition – those substances that can be extracted from cells, tissues or organs with petroleum ether. 3 main types: Simple esters: Waxes Oils and Fats Phosphate Esters Other Lipids Steroids Carotenoids

Fats and Oils Elements: Carbon, Hydrogen, Oxygen Ratio of H to O is very high (20:1) Composed of 2 basic units: GLYCEROL FATTY ACIDS Unsaturated fatty acids have one or more double bond in the hydrocarbon chain. E.g. Olive Oil The double bond creates a ‘kink’ in the hydrocarbon chain.

Fats and Oils Glycerol and Fatty Acids condense to form Fats and Oils: Most Fats and Oils are TRIGLYCERIDES: In fat the fatty acids are saturated In oils the fatty acids are unsaturated Due to the high proportion of unsaturated fatty acids oils are liquid at room temperature. Fats are solid due to saturated fatty acids which can be densely packed together.

Fats and Oils Functions: Thermal insulators Mechanical protection around organs Buoyancy Energy source (most concentrated 38kJ/gm) due to large number of H-O bonds. Water supply from oxidation of fats – Camals and hibernating animals

Phospholipids Diglycerides that react the third hydroxyl group with phosphoric acid. Some have bases joined to phosphate group. Main constituent of cell membranes due to polar nature of molecule. Emulsifying agent in bile. Released in alveoli of lungs to lower surface tension.

Phosphate Esters Phosphoglycerides, e.g. Lecithin Found in cell membranes

Other Lipids Steroids Carbon ring molecules All formed from Cholesterol Testosterone, Oestrogen, Cortisol Carotenoids Pigments found in chloroplasts Trap light energy

Waxes Esters of fatty acids with long chain alcohols. Waterproofing in animals and plants: Animals – insects – waxy cuticle, Human sebaceous glands Plants – Waxy cuticle

Activity Biozone p21 and 22.