What characterizes a macromolecule?

A macromolecule is defined by its large size and complex structure, typically made up of smaller units called monomers that come together to form polymers. The most common macromolecules in biological systems include proteins, nucleic acids, carbohydrates, and lipids. These macromolecules can consist of various types of monomers, leading to an array of structural and functional diversity.

The correct choice points to this characteristic of macromolecules, emphasizing that they can include various polymers. For instance, proteins are polymers made of amino acid monomers, while polysaccharides like starch are composed of multiple sugar molecules. This diversity in the types and arrangements of monomers contributes significantly to the complexity of the macromolecules.

In contrast, macromolecules are not defined by a singular type of monomer or by possessing low molecular mass, which would not typically apply either. Additionally, solubility in water is not a defining characteristic of all macromolecules, as some, like certain lipids, are hydrophobic and do not dissolve well in water.