I did, but because they are listing acetic acid with the fatty ones, doesn't make it a base. It's an organic acid, or more specifically, a carboxylic acid. So are the ones I listed, the only difference being that formic acid (aka methanoic acid) has one fewer Carbon atoms, and the others, propanoic and butanoic, have one and two more Carbons respectively.
I know how they attach the fatty acids to glycerol to make a triglyceride, but I don't know how they build up the long carbon chains. They may be ingested and the structure preserved, or they may be synthesized, etc. I'm sure Hercules will know.