Please clarify the definition of a lipid. Can there be glycerol with ONE fatty acid and one phosphate group and that's it for a lipid (which would create TWO water molecules and leave one of the hydroxyl groups unmodified? Or do all three hydroxyl groups need to react with something?
I think that a monglyceride (as opposed to a triglyceride), or even a phospho-monoglyceride, would still be considered a lipid. (What else could we call it?) Suppose the FA chain is small. At what point does it cease being a lipid? Perhaps when it is no longer soluble in an organic solvent. But such hairsplitting is not all that interesting.