Macromolecular Substances

**Definition:** Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.

**Tree numbers:** - D05

**Synonyms:** - Macromolecular Compounds and Complexes