Figure 10.9. Phosphodiester Bond in DNAWhen a new nucleotide is joined to a growing strand of DNA by a DNA polymerase, it releases an
ester dimer of phosphate, referred to as pyrophosphate denoted PPi, and shown in
Figure 10.10. The hydrolytic release of this molecule provides the energy for the formation of the
new phosphodiester bond. Pyrophosphate is unstable in aqueous solution and is hydrolyzed to form
two molecules of inorganic phosphate, which can then be recycled to form high-energy bonds in
ATP or for other purposes.
Figure 10.10. Pyrophosphate AnionBRIDGE
DNA replication is an important process for the MCAT. Nucleotide triphosphates are added
to the growing daughter strand, with the release of pyrophosphate, PPi. The process of DNA