Which macromolecule contains the most C-C bonds?

• A. Lipids
• B. Carbohydrates
• C. Proteins
• D. Nucleic Acids

Answer: (A)

Carbon–carbon bonds are most abundant in molecules that have long chains of carbon atoms. Lipids, especially triglycerides with three long fatty acid tails, contain extensive hydrocarbon chains where carbon atoms are connected primarily by C–C bonds. Those chains contribute a huge number of C–C bonds to a single molecule.

Carbohydrates are built from sugar units that bring many C–O–C linkages in the repeating units, and while their rings do include C–C bonds within the carbon skeleton, the backbone is interspersed with oxygen linkages, so the overall count of C–C bonds is not as high as in lipids. Proteins have a backbone with peptide bonds (C–N) and side chains that add some C–C bonds, but they don’t feature the lengthy hydrocarbon tails that lipids do. Nucleic acids have a sugar–phosphate backbone with several heteroatom connections (oxygen and phosphorus) and the bases add other bonds, so the dominant C–C bonding is less extensive than in lipids.

Thus, lipids contain the most C–C bonds due to their long hydrocarbon chains.