A macromolecule is a very large molecule, such as a protein. They are composed of thousands of covalently bondedatoms. Many macromolecules are the polymerization of smaller molecules called monomers. The most common macromolecules in biochemistry are biopolymers (nucleic acids, proteins, and carbohydrates) and large non-polymeric molecules such as lipids and macrocycles. Synthetic fibers and experimental materials such as carbon nanotubes are also examples of macromolecules.