Table 1. Phospholipids present in membranes of mammalian cells.
| Phospholipids | Abbreviations | Comments |
|---|---|---|
| Major phospholipids | ||
| Phosphatidylcholine (45–55%) | PC (PtdCho) | Major phospholipid of the cells |
| Phosphatidylethanolamine (15–25%) | PE (PtdEtn) | Major phospholipid of the cells after PC |
| Phosphatidylserine (10–15%) | PS (PtdSer) | Mainly localised to the cytosolic leaflet of the plasma membrane |
| Sphingomyelin (5–10%) | SM | Mainly localised to the outer leaflet of the plasma membrane |
| Phosphatidylinositol (5–10%) | PI (PtdIns) | Inositol headgroup can be phosphorylated at three positions to make seven phosphorylated PIs (Figure 6) |
| Cardiolipin (also known as diphosphatidylglycerol) (2–5%) | CL | Synthesised in mitochondria |
| Minor phospholipids | ||
| Phosphatidic acid | PA (PtdOH) | Intermediate in lipid synthesis; signalling lipid |
| CDP-diacylglycerol (alt. CMP-phosphatidate) | CDP-DAG (CMP-PA) | Metabolic intermediate for PI, PG and CL biosynthesis |
| Phosphatidylglycerol | PG (PtdGro) | Synthesised in mitochondria |
| bis(monoacylglycerol)phosphate (also known as lysobis phosphatidic acid) | BMP (LBPA) | Late endosomes and lysosomes |
The phospholipid composition of a typical cell is indicated. The percentages of the major phospholipids is indicated in parenthesis. The minor lipids are present between 0.5 and 2%. All the phospholipids have a glycerol backbone except sphingomyelin which contains a sphingoid backbone. Two systems are commonly used for the abbreviation of phospholipids. The simpler system is used here such that phosphatidylcholine is abbreviated to PC, not PtdCho. The abbreviations for the other system are provided in parenthesis.