Describe the location and function of the various phospholipids including: cardiolipin (CL), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylinsitol (PI).

  • Cardiolipin (diphosphatidylglycerol) (CL) - located in the inner mitochondrial membrane. It has an anionic charge and the function is unknown, as cardiolipin is not involved in the immune or coagulation systems.
  • Phosphatidylserine (PS) - located in the inner platelet membrane and, during activation, the exterior platelet membrane. It carries an anionic charge, and is the primary phospholipid which promotes the anticoagulant protein C pathway, providing feedback inhibition of thrombin formation.
  • Phosphatidylethanolamine (PE) - located in both the interior and exterior of cell membranes. It carries a neutral (zwitterionic) charge, and promotes the anticoagulant protein C pathway, but to a lesser degree than PS.
  • Phosphatidylcholine (PC) - located in the interior and exterior of cell membranes. It carries a neutral charge, and promotes the anticoagulant protein C pathway, but to a lesser degree than PS.
  • Phosphatidylinsitol (PI) - located in the interior and exterior of cell membranes. It carries a cationic charge, and promotes the anticoagulant protein C pathway, but to a lesser degree than PS.