Question

4. Which type of macromolecules is NOT typically made of chains of linked monomers: complex carbs; lipids; proteins; nucleic acids; none of the above

Answer 1

Answer: Lipids are not formed by monomers linked to form a chain.

Explanation for the answer:

Macromolecules are structurally long molecules with a chain-like appearance and made up of repeating units. These repeating units are known as monomers. Monomers act as links in the polymer chain. In biology, there are four main macromolecules, namely, carbohydrates, proteins, lipids and nucleic acids.

Each of these is polymer composed of monomeric repeating units, except for lipids. Although lipids have a massive backbone and are structurally large, but they are not considered as polymers. This is because lipids are devoid of monomers, and polymers are made up of monomers. Also, the basic units in lipid structure are fatty acids and glycerol molecules, and they do not form repetitive chains. In case of lipids, ester bond is formed between them during the condensation reaction.

The complex carbohydrates include starch and cellulose. Complex carbohydrates have many sugar monomers or monosaccharides linked in a row. Both starch and cellulose have glucose as their repeating unit or monomer. The only difference is that starch has glucose units oriented in the same direction, unlike in cellulose. Proteins have amino acids as monomers linked by peptide bonds to form a chain-like structure. Similarly, nucleic acids have nucleotides as monomeric units. Each nucleotide is made up of a five-carbon sugar, phosphate group and a nitrogenous base.

Hence, except lipids, all the macromolecules like proteins, complex carbohydrates and nucleic acids are polymers composed of monomeric repeating units.