ABSTRACT
Phospholipids (PL) are amphiphilic molecules with
lipophilic acyl chains and a hydrophilic head. Gene-
rally, two main types of phospholipids can be found in
living tissues. A first group, the glycerophospholipids, consist of a
glycerol backbone with two fatty acids esterified at
position sn-1 or sn-2. On the third hydroxyl, a phos-
phate residue is bound on to which different organic
bases or other complex organic groups may be linked.
Generally, the fatty acid chain on the sn-1 position
is more saturated compared to the one at the sn-2
position on the glycerol moiety. Lysophospholipids
(LPC, LPE, etc.) contain only one acyl group, which is
predominantly esterified at the sn-1 position. Apart
from diacyl forms, some phospholipid species from
animal and microbial origin have an ether or vinyl
ether linkage at the sn-1 position, and are denoted
as alkylacyl-and alkenylacyl-glycerophospholipids,
respectively. The latter form is also known as plasma-
logen. The polar organic base on the phosphate
determines the type of phospholipid. Phosphatidic
acid (PA) is an important intermediate in the biosynth-
esis of triglycerides and phospholipids; however, it is
only present in very small amounts in living tissue.
The concentration of this acidic phospholipid is often
overestimated due to enzymatic hydrolysis of other
phospholipids by phospholipase D. Phosphatidylgly-
cerol (PG) is present in the mitochondria of bacteria
and in chloroplasts of plants. In animal tissues it serves
