Lipids are composed of carbon, oxygen and hydrogen. They’re insoluble in water and carry out a number of functions including:

• energy storage
• insulation
• protection
• hormones
• buoyancy

They’re also important in biological membranes.

They consist of two molecules: glycerol and fatty acids.

Glycerol is composed of three carbon atoms to which is attached a hydroxly group and hydrogen atoms.

Fatty acids, on the other hand, are composed of an acid group at one end of which is attached a hydrocarbon chain known as R.

This R-group can be either:

• saturated which means that all possible bonds are made with hydrogen atoms leaving no room for any C=C bonds
• unsaturated which do contain C=C bonds (monounsaturated fatty acids contains one C=C bond whereas polyunsaturated contain more than one)

Unsaturated fats are fluid at room temperature whereas saturated fats are solid. Animals tend to contain more saturated fats while plants tend to contain more unsaturated.

Lipids which contain one glycerol molecule and three fatty acids are known as triglycerides. The molecules are bonded together by covalent bonds known as Ester bonds which are created through a condensation reaction.