During chemical analysis of a cell, when we segregate the chemical components, two fractions are obtained, ajd soluble pool and acid insoluble pool. The biomolecules found in acid soluble pool include proteins, lipids, polysaccharides and nucleic acids. Except lipids, all of these have molecular weights in the range of ten thousand daltons and above and are termed biomacromolecules.
Lipids have molecular weights of about 800 Da or below and thus, are micromolecules. Still, they separate in the macromolecular fraction because when we disrupt a cell, the membranes are broken into pieces and form small water insoluble vesicles (which mainly contain lipids), which separate in the acid insoluble pool.