3.10
Nucleotides consist of a base, a pentose sugar, and a phosphate group.
Nucleotides polymerize when phosphate and a hydroxyl group of sugar are linked via a condensation reaction to form nucleic acids, such as DNA.
Since there are two ester bonds connecting two nucleotides, the linkage is called a phosphodiester bond.
The first ester bond already exists between the phosphate group and the 5'-carbon atom of the pentose sugar of one nucleotide, and the second ester bond forms between the hydroxyl group of the phosphate and the 3'-carbon atom of the pentose sugar of the preceding nucleotide.
For each ester bond formed, a water molecule is released.
As more nucleotides are added through phosphodiester bonds, the polynucleotide chain grows to create the sugar-phosphate backbone.