 Lipids: a large and varied group of organic compounds.  Lipids include: Triglycerides Phospholipids Waxes Cholesterol and Steroids  Lipids are all non-polar and do not dissolve in water

 Triglycerides are one of the most common types of lipids  Triglycerides consist of one molecule of glycerol bonded to three fatty acid molecules  Each fatty acid is linked to the glycerol molecule by an ester bond C H OH Glycerol Hydroxyl groups

Carboxyl group Fatty Acids: General Formula: CH3 (CH2)n C O OH CH3 H C O OH CH2

H C O OH Can be drawn as: C O OH

This is a condensation reaction Forming a monoglyceride: C O OH C H OH Hydroxyl group and carboxyl group react Ester bond C H OH O + H2O This is a condensation reaction

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

This is a hydrolysis reaction To split these ester bonds and separate a fatty acid from glycerol we need to add a molecule of water C H OH O C H OH + H2O C O OH This is a hydrolysis reaction

Uses of Lipids in Living Things 1. Long-term energy stores Human Adipose Tissue Plant Oils

2. Buoyancy for marine. animals: lipids are less. dense than water so 2. Buoyancy for marine animals: lipids are less dense than water so help animals float 3. Insulation: a layer of fat beneath the skin cuts down heat loss

Camels’ humps are made of fat 4. Production of water: fatty acids produce a lot of metabolic water when they are oxidised during respiration e.g. C17H35COOH + 26 O2  18 CO2 + 18 H2O (a typical fatty acid) Camels’ humps are made of fat

Homework: Compare the relative advantages and disadvantages to an organism of using carbohydrates and lipids as energy stores To be handed in on a separate sheet of paper.