Why do lipids whose molecular weights do not exceed 800 Da. cone under ACID INSOLUBLE FRACTION,i.e. macromolecular fraction?

Becsuse lipids are arranged into structurelike cell membrane and other membrane and when the tissue is grinded with help of mortar and pestle cell membrane is disrupted into pieces and form vesicle like structure which are insoluble in water therefore these membrane fragments in form of vesicles got separated alongwith acid insoluble pool in macromolecular fraction otherwise lipids are not srtictly macromolecules