Lipids are biomolecules that are soluble in organic non-polar solvents and are hence insoluble in water. Glycerides and waxes form a sub-group, which have an ester as the major functional group and include triglycerides and phospholipids. Another diverse group of compounds which do not have any ester functional groups are also classified as lipids. Lipids without ester functional groups include: steroids, fatty acids, soaps, sphingolipids, and prostaglandins. Fatty Acids Glycerides Non-glyceride Lipids Steroids Applications of Lipids