Both DNA and RNA contain nucleotides with similar components. In RNA, the sugar component is ribose, as indicated by the name "ribonucleic acid". In DNA, or deoxyribonucleic acid, the sugar component is deoxyribose. The prefix deoxy means that an oxygen atom is missing from one of the ribose Carbon atoms.
When a sugar bonds together with a Nitrogen base, you now have two of the three components of a nucleotide. This structure is known as a nucleoside.
There are FIVE Nitrogen bases that are found in DNA and RNA (although Uracil is found ONLY in RNA!). These five bases are divided into two categories based on their molecular structure. Click onto the hyperlinks and look at the structures below to see if you can tell what differentiates each category!
1 purines (Adenine and Guanine)
2 pyrimidines (Thymine, Cytosine, and Uracil)
You should notice that the purines have two ring structures while pyrimidines have only one ring structure. The way I've always remembered the difference is that the LONGER word (pyrimidine) represents the SMALLER structure (only one ring), and vice-versa!