Formation of a phosphodiester bond between two nucleotides is energetically unfavorable reaction How is then DNA synthesis driven forward O The phosphodiester bond forms between the 3 hydroxyl of the ribose at the end of the growing chain and the alpha phosphate of the incoming nucleotide A molecule of pyrophosphate PPI is released in the process and is further hydrolyzed into inorganic phosphate P Thus a net of one high energy bond is consumed in the process which drives the process forward PPP 5 DNA 3 OH dNTP PPP 5 DNAn 1 3 OH PPI 2Pi The polymerase is hydrolyzing an ATP molecule the general currency molecule of the cell for every new nucleotide that is added to the growing chain Thus a net of two high energy bonds are consumed in the process which drives the process forward PPP 5 DNA 3 OH dNTP ATP PPP 5 DNAn 1 3 OH PPI 2Pi The phosphodiester bond forms between the 3 hydroxyl of the ribose of the incoming nucleotide and the alpha phosphate at the 5 end of the the growing chain A molecule of pyrophosphate PPI is released in the process and is further hydrolyzed into inorganic phosphate Pi Thus a net of one high energy bond is consumed in the process which drives the process forward dNTP OH PPP 5 DNA 3 OH PPP 5 DNAn 1 3 OH PPI 2Pi