Final answer:
Lipids are not formed by polymerization, unlike the other classes of biological macromolecules such as proteins, carbohydrates, and nucleic acids, which are formed by linking together monomers in a chain. The correct answer is option 2) lipids
Step-by-step explanation:
Macromolecules and Polymerization
In biology, there are four major classes of biological macromolecules: proteins, carbohydrates (polysaccharides), nucleic acids (DNA and RNA), and lipids. Among these, the one that is NOT formed by polymerization is lipids. Proteins, carbohydrates, and nucleic acids are formed through polymerization, which is a process of creating complex molecules by linking together simpler units called monomers, using covalent bonds. Lipids, however, are not formed in this way; they are constructed from smaller molecules that do not polymerize in the same manner as the other three.
Proteins are formed by amino acids linking together via peptide bonds in a dehydration reaction. Carbohydrates are built from monosaccharides joining by glycosidic bonds, while nucleic acids like DNA and RNA are composed of nucleotides which are linked by phosphodiester bonds. The common feature among proteins, carbohydrates, and nucleic acids is that they undergo dehydration synthesis, where monomers combine with the release of water molecules.
Lipids, on the other hand, typically consist of glycerol bonded to fatty acids and are not considered polymers because their assembly does not involve a repetitive linkage of monomeric units in a chain. Instead, they form through other types of reactions, like esterification, which does not produce polymer chains. The four major classes of biological macromolecules are essential for various cellular functions, from creating structures in the body to storing genetic information.