The phosphatidic acid (PA) is an anionic lipid consisting of a negatively charged phosphomonoester headgroup attached to a hydrophobic diacylglycerol backbone. It is the simplest glycerophospholipid naturally occurring in all living organisms, and even though its content is minor in comparison to other cellular lipids, it is attracting more and more attention due to its various biological functions. Learn more about pa phosphatidic acid: https://www.creative-biolabs.com/lipid-based-delivery/phosphatidic-acid-pa.htm