What process provides the energy necessary for the addition of nucleotides to a growing DNA chain during replication?

The addition of nucleotides to a growing DNA chain during replication is driven by the hydrolysis of pyrophosphate, which is a byproduct of nucleotide incorporation. When a nucleotide is added to the growing DNA strand, it is first incorporated in the form of a deoxynucleotide triphosphate (dNTP). The process involves the formation of a phosphodiester bond, during which the terminal phosphate group of the incoming nucleotide is released as pyrophosphate (PPi). Hydrolysis of this pyrophosphate into two inorganic phosphates (2 Pi) provides the necessary energy to drive the reaction forward and ensures that the addition of nucleotides is energetically favorable.

This process is crucial for the overall directionality and rate of DNA synthesis, allowing for the continuous elongation of the DNA strand. The energy provided by pyrophosphate hydrolysis is effectively harnessed, effectively "paying for" the addition of each nucleotide and facilitating accurate and efficient DNA replication.