Lipids: Fats & Oils 2003-2004

Concentrated energy molecules Lipids Concentrated energy molecules 2003-2004

Lipids Examples fats oils waxes hormones sex hormones testosterone (male) estrogen (female) 2003-2004

What are the functions of lipids?   STRUCTURAL: biological membranes (phospholipids, steroids, glycolipids), cushioning (fat deposits round the kidneys) ELECTRICAL INSULATION: myelin sheath round axons THERMAL INSULATION: subcutaneous fat deposits. WATER PROOFING: waxes and oils ENERGY STORE AND SUBSTRATE: very condensed form of energy (37 kJ g-1) used by animals and seeds. HORMONES: steroids VITAMINS: precursor to Vit D BUOYANCY: oil droplets in plankton 2003-2004

Fatty acids: carboxylic acid + long hydrocarbon chain OH CH3 Carboxylic acid Hydrocarbon chain A saturated fatty acid An unsaturated fatty acid C O OH CH3 © 2007 Paul Billiet ODWS

Condensation in triglycerides fatty acids + glycerol (1, 2 or 3 = mono , di or triglycerides) C O OH CH3 HO – CH2 HO - CH2 HO - CH C O OH CH3 Condensation reactions © 2007 Paul Billiet ODWS

2003-2004

Two fatty acids joining glycerol = A diglyceride CH3 O - CH3 HO - CH3 O - CH + 2H20 © 2007 Paul Billiet ODWS

Molecular Structure of Fat not a chain (polymer) = just a “big fat molecule” 2003-2004

A TRIGLYCERIDE: C H O Glycerol Fatty acid Can be drawn as: Ester bond

Unsaturated fatty acids no double bonds one or more double bonds abundant in fats abundant in oils more reduced less reduced more energy less energy high melting point low melting point © 2007 Paul Billiet ODWS

Saturated fats Most animal fats Limit the amount in your diet solid at room temperature Limit the amount in your diet contributes to heart disease deposits in arteries 2003-2004

Unsaturated fats Plant, vegetable & fish fats liquid at room temperature the fat molecules don’t stack tightly together Better choice in your diet 2003-2004

Saturated vs. unsaturated  2003-2004

Other lipids in biology Cholesterol good molecule in cell membranes make hormones from it including sex hormones but too much cholesterol in blood may lead to heart disease 2003-2004

Other lipids in biology Cell membranes are made out of lipids phospholipids heads are on the outside touching water “like” water tails are on inside away from water “scared” of water forms a barrier between the cell & the outside 2003-2004

Other lipids Steroids: multiple ring structures (e.g. cholesterol) Functions: cell membrane structure, digestion (help to emulsify fats), hormones (testosterone etc), vitamins (e.g. Vitamin D), poisons Waxes: long chain alcohol + fatty acids Water proof coating to leaves, fur feathers, insect exoskeletons. Used by bees to construct their honey combs. © 2007 Paul Billiet ODWS

Compare the use of carbohydrates and lipids in energy storage. Stored as…? Starch in plants and glycogen in animals Triglycerides or fat in animals and oils in plants Long/short term storage? Short time storage Long time storage Ease of digestion/ release of energy? Easily broken down to release energy quickly. More complex and so slower to brake down. Energy per gram? 17 kJ per gram 38 kJ per gram Solubility in water? (and consequence) Soluble in warm water and insoluble in cold water Insoluble in water Use of oxygen in metabolism? May be used for anaerobic respiration temporarily in muscle cells. In this case lactic acid will be produced. Only for aerobic respiration 2003-2004