Introduction to Lipids

Abstract

Historically, biological materials have been classified as fats, proteins, carbohydrates, and minerals. One of the main characteristics that distinguishes fats from the other natural products is their solubility in non-polar solvents such as ether, chloroform, benzene, etc., and their insolubility in water. These organic solvent-soluble substances have been grouped according to their physical state at room temperature; hard solids, soft solids, and liquids have been called waxes, fats, and oils, respectively. The heterogeneity of ‘fat extracts¹ has become evident with the development of more efficient extraction procedures, and particularly with the development and application of chromatographic techniques to the separation of the extract components. ‘Fat extracts’ may be composed of a complex mixture of substances with widely different chemical structures, but with similar solubilities in organic solvents. The term presently used to include this diverse group of substances is Lipid. Lipids are still most often defined according to their solubility properties.