1.3 Lipids

Structure of triglycerides

A glycerol molecule and three fatty acids

Formula for glycerol

C3H8O3 or C3H5(OH)3

Fatty acids

A hydrocarbon chain with a carboxyl group at one end

How are glycerol and fatty acids bonded

Condensation reaction

Name of bond between fatty acid and glycerol

Ester bond

What makes a fatty acid unsaturated

A carbon carbon double bond

Saturated fatty acid

No carbon carbon double bond

Why are unsaturated fatty acids more likely to be liquid at room temperature

The carbon carbon double bond makes the fatty acid curved and less compact

What decreases at number of carbon carbon double bonds increases

Melting point

Structure of phospholipids

Remove a fatty acid and replace it with an inorganic phosphate group

Why are phospholipids polar?

Fatty acids are hydrophobic, but the phosphate group is hydrophilic

Emulsion test:

• Add ethanol

• Then water

• Positive = white emulsion

Characteristics of lipids:

• Hydrogen carbon and oxygen

• Smaller proportion of oxygen compared to carbohydrates

• Insoluble in water

• Soluble in organic solvents like alcohols and acetone

Difference between fats and oils

Fats are solid at room temperature, oils are liquid

Roles of lipids

• Phospholipids are used in cell membranes

• Release energy when oxidised

• Used as waterproofing in waxy cuticles and oily secretion

• Insulation as its a slow conductor of heat

• Protection of organs like kidneys