These important lipids
are widely distributed in plants, bacteria and animals. They are the major constituents
of cell membranes but are found also in circulating fluids.
They can be classified into three main groups:
1 - Lipids with a phosphate residue, one glycerol, or an aminoalcohol or a fatty alcohol, without or with one or two fatty chains (exceptionally one inositol group, two phosphates or four fatty chains):
2 - Lipids containing a glycosidic moiety with a glycerol or an aminoalcohol and with fatty chain(s) (sometimes with one or more phosphate groups):
3 - Lipids without phosphate group and containing one amino acid linked to long-chain alcohol and acids: