TeXes Science Practice Test

Among the following macromolecules, which one is NOT considered a polymer?

1. Proteins

2. Carbohydrates

3. Lipids

4. Nucleic acids

The correct answer is: Lipids

The correct answer highlights that lipids are not considered true polymers like the other macromolecules listed. Polymers are large molecules made up of repeating subunits called monomers linked together through covalent bonds. Proteins, carbohydrates, and nucleic acids are all classified as polymers because they are composed of long chains of repeating units. For instance, proteins are made from amino acid monomers, carbohydrates are made from sugar monomers, and nucleic acids are composed of nucleotide monomers. Each of these macromolecules consists of a defined structure with repeating units that can be assembled in various configurations. In contrast, lipids do not consist of the same type of monomeric repeating units. Instead, lipids include a diverse group of molecules such as fats, oils, and steroids, which are generally characterized by hydrophobic properties rather than a long chain of repeating units. While some lipids, like phospholipids, do have a back-to-back arrangement, they do not fit the traditional polymer structure seen in proteins, carbohydrates, and nucleic acids. Therefore, the distinction lies in the structural characteristics and assembly of the molecules, leading to the conclusion that lipids are not classified as polymers.