Phosphodiester bonds are formed through which type of reaction?

• A. Hydrolysis
• B. Oxidation
• C. Reduction
• D. Condensation reactions

Answer: (D)

Condensation reactions drive the formation of phosphodiester bonds. When nucleotides are linked to build DNA or RNA, the 5' phosphate of one nucleotide and the 3' hydroxyl of the adjacent nucleotide react, releasing a molecule of water and creating a covalent phosphodiester linkage that forms the sugar–phosphate backbone. In cells, the process is powered by the energy from nucleoside triphosphates, with the reaction producing pyrophosphate as a byproduct, which helps push the bond formation forward. Hydrolysis would do the opposite, breaking phosphodiester bonds by adding water, while oxidation and reduction involve electron transfer and are not the type of reaction that forms these links.