So the cell, including eukaryotic and prokaryotic cells, can use the DNA molecules to synthesize proteins and enzymes that are necessary for the cell survival. And in fact, whenever our cell or organism reproduces, each individual cell must replicate the DNA molecule and pass it down to the offspring. Now, what exactly is the composition of DNA? So, in the same way that proteins consist of individual units known as amino acids, DNA molecules are also polymers, meaning they consist of individual subunits known as nucleotides. And any given nucleotide consists of three parts. So we have a deoxyribo sugar, which is a five member sugar.