What defines a macromolecule or polymer?

A macromolecule or polymer is defined as a very large molecule composed of many repeated smaller subunits, known as monomers. These monomers are joined together through various types of chemical bonds, typically covalent bonds, to form a chain-like structure, which can be highly complex and serve various functions in biological organisms. For example, proteins are polymers made up of amino acid monomers, carbohydrates consist of sugar monomers, and nucleic acids are formed from nucleotide monomers.

The characteristic of being composed of repeated smaller subunits is essential to the definition of macromolecules, as it highlights their structural organization and functionality in biological systems. This structural arrangement allows macromolecules to perform diverse roles, such as serving as enzymes, structural components, or energy storage molecules in living organisms. Other characteristics, such as solubility, size, or single-type composition, do not fully capture the essence of what defines macromolecules, reinforcing why this definition is the most accurate.