A molecule is a smallest particle of a substance (usually non-living) while a biomolecule is the smallest particle of a living substance. Molecule can be organic or inorganic while biomolecule is organic. Molecules can be simple or complex but biomolecules are the complex molecules. A molecule can consist of any element found in the periodic table while a biomolecule consists of carbon, hydrogen, nitrogen and oxygen only. Moreover, molecules are combined to form compounds and they cannot be categorized further while bimolecular can be categorized as monomers, small molecules or polymers.
