3.1.3 - Lipids

Thursday 21st September ‘23

Scientific name for molecules found in fats & lipids.

Functions:

• Major source of energy in the diet

• Used to store energy (eg Adipose tissue which is found under human skin).

• Helps to insulate the body, reducing heat loss to the environment. Also found around internal organs to protect from injury.

• Waterproofing (eg oils which coat feathers of aquatic birds).

• Major part of the structure of membranes (such as those which surround cells and mitochondria).

Fatty acid molecules:

• Hydrocarbon chain (can be monounsaturated, polyunsaturated or saturated). The large number of carbon and hydrogen atoms cause lots of energy to be released from lipids.

• Carboxylic group (COOH) forms ester bonds with the three hydroxyl group. Ester bonds are broken by lipase enzymes in a hydrolysis reaction (requires 3 water molecules).

Glycerol molecule:

• Three hydroxyl groups so esterification (condensation reaction) happens thrice.

Triglycerides

• 1x glycerol, 3x fatty acids

• Non-polar so hydrophobic. They are insoluble as they face inwards, and the glycerol heads shield them from water.

Phospholipds

• 1x glycerol, 2x fatty acids, 1x negative phosphate ion