What are compound lipids? Mention their biological significance.

Compound lipids: 

a. These are ester of fatty acids containing other groups like phosphate (Phospholipids), sugar (glycolipids), etc. 

b. They contain a molecule of glycerol, two molecules of fatty acids and a phosphate group or simple sugar. 

c. Some phospholipids such as lecithin also have a nitrogenous compound attached to the phosphate group.

d. Phospholipids have both hydrophilic polar groups (phosphate and nitrogenous group) and hydrophobic non-polar groups (hydrocarbon chains of fatty acids). 

e. Glycolipids contain glycerol, fatty acids, simple sugars such as galactose. They are also called cerebrosides. 

Biological significance: 

a. Phospholipids contribute in the formation of cell membrane. 

b. Large amounts of glycolipids are found in the brain white matter and myelin sheath.