Nucleotides are the basic structural units of nucleic acids, which control the production of proteins in living organisms. The nucleotides are made up of a phosphate group, a pentose sugar, and a nitrogen base.
This shows the basic structure of a nucleotide. This example has the sugar ribose, and is characteristic of RNA. The nucleotide could contain the sugar deoxyribose, characteristic of DNA. For DNA, the bases may be adenine, guanine, cytosine or thymine. For RNA the bases are adenine, guanine, cytosine and uracil.