ABSTRACT
By dežnition, these simple lipids with a low polarity contain only two types of components, one at least is a lipid, the other being another simple lipid, a glycerol, one or several amino acids, or a carbohydrate. Thus, these simple lipids can form various combinations:
• A glycerol esterižed by one or more fatty acids (Section 2.1, Acylglycerols) • A glycerol linked to one or more fatty alcohols (Section 2.2, Alkylglycerols) • One or more amino acids linked to one or two fatty acids (Section 2.3,
Simple Aminolipids) • An amino alcohol linked to one fatty acid (Section 2.4, Ceramides) • A fatty alcohol esterižed by one fatty acid (Section 2.5, Waxes) • One or two fatty acids esterižed by a dihydroxynitrile group (Section
2.6, Cyanolipids) • A sterol esterižed by a fatty acid or linked to an alcohol (Section 2.7, Sterol
Esters and Sterol Alkyl Ethers) • A fatty acid linked to coenzyme A (Section 2.8, Acyl-CoA) • A simple lipid linked to a carbohydrate (Section 2.9, Simple Glycolipids)
These lipids are also called glycerides. This group includes the monoacylglycerols, the diacylglycerols, and the triacylglycerols, when they are formed of a glycerol esterižed, respectively, by one, two, or three fatty acids (sometimes one or two phenolic acids). In order to locate the position of fatty acids on the glycerol molecule, a precise nomenclature was established in 1967 to number the carbon atoms of the glycerol (commission of the biochemical nomenclature, International Union of Pure and Applied Chemistry-International Union of Biochemistry [IUPAC-IUB]). Thus, by using the Fischer projection (Figure 2.1), if the secondary alcohol group is directed toward the left of carbon 2 (C-2), the carbon above carbon 2 is called carbon-1 (C-1) and the other is called carbon 3 (C-3).
