Phosphatidylethanolamine is the most abundant phospholipid in prokaryotes and the second most abundant in the membranes of mammalian, plant, and yeast cells, comprising approximately 25% of total mammalian phospholipids. In the brain, it constitutes nearly half of the total phospholipids. It is mainly synthesized through the cytidine diphosphate-ethanolamine and phosphatidylserine decarboxylation pathways, which occur in the endoplasmic reticulum (ER) and mitochondrial membranes, respectively. Phosphatidylethanolamine serves as a precursor for the synthesis of phosphatidylcholine and arachidonoyl ethanolamide and provides ethanolamine for various cellular functions. In E. coli, its deficiency prevents proper assembly of lactose permease, suggesting a chaperone role. It acts as a cofactor in prion propagation in vitro and can convert recombinant mammalian proteins into infectious molecules in the absence of RNA. Phosphatidylethanolamines (soy) denotes a mixture of phosphatidylethanolamines isolated from soy with various fatty acyl groups at the sn-1 and sn-2 positions.