How do nucleotides polymerize to form nucleic acids?
The polymerization reaction is mediated by an enzyme, but the overall reaction is basically an esterification reaction between an alcohol and a phospho acid. The alcohol group is located on the 3
end of the sugar of the nucleotide, and the phospho acid group is on the 5 end of the next reacting nucleotide.
Lets say nucleotide 1 will be the first nucleotide. It has a 3` OH on its sugar, and this OH will act as the alcohol group.
Nucleotide 2 has a HOPO3-Sugar-OH linkage (just like nucleotide 1), and the HO part of HOPO3 on nucleotide 2 reacts with the 3` OH on nucleotide 1 and you get an esterification reaction in which a phosphodiester bond is formed
Nuc1-O-P-O3-Nuc2, and now the two nucleotides are linked. This reaction happens over and over and over to make a long single strand chain of DNA or RNA.
In the cell, the HO-PO3-sugar group is actually a triphosphate (HO-PO3-PO3-PO3-sugar), and the extra phosphate groups just provide the needed energy to get the process moving.