Which Macromolecule Is Not a Polymer?

Unlike the other biological macromolecules, lipids are not polymers. Polymers are long chains of smaller repeating elements. DNA, carbohydrates and proteins are all polymers because they consist of chains of nucleotides, simple sugars and amino acids respectively. These macromolecules must be polymers by definition.

The closest lipids to polymers are triglycerides. These lipids are formed by multiple fatty acid chains connected to a glycerol backbone. However, lipids can have non-repeating ring structures or consist of a single fatty acid chain. Lipid structure consists of long chains or ring structures with only carbon and hydrogen atoms. As a result, lipids are "hydrophobic" and do not interact with water.