Biological Chemistry - Berezov, T. T., & Korovkin, B. F. 1998

Chemistry of Lipids
Biological Role of Lipids

Lipids comprise a diverse group of compounds that vary significantly in their chemical Structure and biological Functions. Consequently, it is difficult to formulate a single definition that would encompass all compounds belonging to this Class.

Broadly speaking, lipids are defined by several key characteristics: insolubility in Water; solubility in non-polar Solvents such as ether, chloroform, or benzene; the presence of higher alkyl radicals; and widespread occurrence in living organisms.

This definition encompasses a wide range of substances, including some typically classified under other chemical groups, such as Fat-soluble Vitamins and their derivatives, carotenoids, higher Hydrocarbons, and alcohols. Including these substances among lipids is justified to a certain extent because, in living organisms, they are found alongside lipids and are co-extracted with them by non-polar solvents. On the other hand, certain lipids are quite soluble in water (for instance, lysolecithins). The term “lipids” is more comprehensive than “lipoids,” which refers specifically to a group of fat-like substances such as Phospholipids, sterols, Sphingolipids, and others.

Lipids play a vital role in physiological processes. As a fundamental component of Introduction/36.html">Biological Membranes, they influence membrane permeability and participate in Nerve Impulse transmission and intercellular contacts. Fat serves as a highly efficient energy source in the body, either directly or as stored energy in adipose tissue. Natural dietary fats contain fat-soluble vitamins and Essential Fatty acids. Another crucial function of lipids is providing thermal insulation in animals and plants, as well as protecting Organs and Tissues from mechanical trauma.