The common characteristic of all lipids is they are hydrophobic, so they are insoluble in polar solvents, such as water. They are, however, soluble in at least one non-polar organic solvent. The reason lipids are hydrophobic is that their molecules have long hydrocarbon chains with 16 to 18 carbon atoms.
The hydrophobic nature of lipids influences their functions in organisms. They are structural components of cell membranes, steroid hormones, pigments and waxes. They also act as energy storage molecules, metabolism regulators and emulsifying agents, according to the University of Calgary. Other major classes of organic biomolecules, including proteins, carbohydrates, nucleic acids and amino acids, are more soluble in water than they are in organic solvents.