Describe the role of lipids.

Lipids are a great energy reserve in both plants and animals. 
This is due to the greater number of carbon-hydrogen bonds present in comparison to carbohydrates.

It also acts as an insulator against heat loss, and can provide protection for delicated organs such as the kidneys, due to it being stored around them. 

Finally, lipids are insoluble in water and are important in land organisms such as insects, where the waxy cuticle is crucial in reducing water loss.