Some examples of lipids include cholesterol and steroids, vegetable oil, butter, phospholipids, waxes and fat-soluble vitamins. Lipids are compounds that are insoluble in water but soluble in one or more organic solvents.
Lipids have several functions in organisms. They are a structural component of the cell membrane. They are used as signaling molecules, as is the case with steroids. They are also used for energy storage. The most common class of lipids is triglycerides, which are fats and oils. The second most common class of lipids is phospholipids, the lipids that make up the cell membrane in animals and plants.