3.1.3 Lipids

2 types of lipids:

Triglycerides + Phospholipids

Structure of triglycerides:

• 3 fatty acid chains

• 1 glycerol molecule

Components of phospholipids:

• 2 fatty acid chains

• Glycerol molecule

• 1 phosphate group

Bond formed between glycerol and fatty acids during a condensation reaction:

Ester bond

Definition of Saturated lipids:

Lipids that only contain single carbon-carbon bonds mainly found in animals.

Definition of unsaturated lipids and facts:

• Lipids that have at least one carbon-carbon double bond and are found in plants.

• Cannot pack closely together and are liquid at room temperature

Structure and properties of triglycerides:

• High ratio of energy-storing C-H bonds: C atoms - excellent energy store

• Low mass: Energy ratio - more energy can be stored with less mass

• Large and non-polar - doesn't affect the water potential of cells

• High ratio of H-O atoms - releases water when oxidised

Structure and properties of phospholipids

• Hydrophillic head (polar): Phosphate group

• Hydrophobic body (non-polar): Rest of phospholipid

• Allows the formation of the Phospholipid bilayer at the cell surface membrane

Test for Lipids:

Emulsion test:

• Add Ethanol to the sample and shake.

• Add the mixture to distilled water.

• Positive result: A milky white emulsion forms.