Biomacromolecules are large biomolecules with molecular weights greater than 10,000 Da. They are found in the acid-insoluble fraction of cells and include proteins, nucleic acids (DNA and RNA), and polysaccharides. These are generally polymeric molecules made up of repeating smaller units (monomers).

The acid-soluble fraction contains micromolecules, such as amino acids, sugars, nucleotides, and other small molecules, with molecular weights ranging from 18 to about 800 Da.

Although lipids have low molecular weights (usually less than 800 Da), they are present in the acid-insoluble fraction because they are organized into cell membranes. When cells are broken, membrane fragments form insoluble vesicles, causing lipids to separate with the acid-insoluble fraction. Therefore, lipids are not true biomacromolecules.

Key Facts (NEET/CBSE)

• Micromolecules: Molecular weight < 1000 Da (acid-soluble fraction).
• Biomacromolecules: Molecular weight > 10,000 Da (acid-insoluble fraction).
• Examples of biomacromolecules: Proteins, nucleic acids, polysaccharides.
• Lipids are an exception: Present in the acid-insoluble fraction but not true macromolecules.
• Water is the most abundant chemical in living organisms.