Final answer:
The energy for forming a phosphodiester bond comes from the hydrolysis of the incoming nucleotide triphosphate (NTP), which releases energy by cleaving off two phosphate groups (pyrophosphate).
Step-by-step explanation:
The energy required for the formation of the new phosphodiester bond during polymerization is supplied by the hydrolysis of the incoming nucleotide triphosphate (NTP). This process involves breaking high-energy bonds, specifically the bonds between the phosphate groups (phosphoanhydride bonds). When an NTP is added to a nucleic acid chain, two phosphates (pyrophosphate) are cleaved off. This process releases energy which is then used to form the phosphodiester linkage between the growing nucleic acid chain and the incoming nucleotide. The pyrophosphate is further hydrolyzed into two inorganic phosphates, thereby making the polymerization energetically favorable. It's the release of energy during the hydrolysis of pyrophosphate that drives the polymerization reaction forward.