Definition of Macromolecule
A macromolecule is a very large molecule that has a diameter of about 100 to 10k angstroms. They are the polymers of small molecules that have distinct characteristics. They are composed of thousands of atoms. The synthetic polymers (plastics), natural fibers (cotton), and biologically important constituents like protein, nucleic acids (DNA, RNA), carbohydrates are macromolecules. The proteins are the polymers of amino acids. The amino acids link together to form polypeptides through peptide linkage and these polypeptides then give rise to protein molecules.
The nucleic acids are formed by the combination of nucleotides joined together by phosphodiester linkages. In the same way, the polysaccharides are larger molecules which are the polymers of monosaccharides (simple sugars) that are linked to one another through glycosidic linkages. These macromolecules are pivotal for the normal functioning of a body and to sustain life.