What forms the backbone of a nucleic acid molecule?

The backbone of a nucleic acid molecule is formed by a repeating structure of phosphate and sugar components, specifically deoxyribose in DNA and ribose in RNA. This backbone provides structural stability to the molecule and allows for the attachment of nitrogenous bases, which carry the genetic information. The phosphate groups connect to the sugar molecules, and this alternation between the phosphate and sugar creates a strong, stable chain that supports the overall structure of the nucleic acid.

Amino acids, carbohydrates, and fatty acids do not play a role in forming the backbone of nucleic acids. Amino acids are the building blocks of proteins, carbohydrates serve as energy sources or structural components in cells, and fatty acids are components of lipids, none of which contribute to the structure of nucleic acids. Thus, the correct understanding centers around the essential role of phosphate and sugar in forming the nucleic acid backbone.