The DNA molecule is made up of three chemical elements. Nitrogen bases, pentose sugars and phosphoric acid.
1. Nitrogen Alkali: This alkali is formed by carbon, hydrogen, oxygen and nitrogen. Alkaline compounds form rings. Based on the number of rings, nitrogenous bases can be divided into two groups.
(i) Purines: Dicyclic nitrogenous bases are called purines. Its common symbol is C5H4N4. It is composed of adenine and guanine.
(ii) Pyrimidine: A cyclic nitrogenous base is called pyrimidine. Its common symbol is C4H4N2. It is composed of thymine and cytosine.
2. Pentose sugar: Five carbon sugar (sugar) is called pentose sugar. DNA molecules contain deoxyribose sugar. It is a type of monosaccharide. Deoxyribose sugar is so named because carbon number 2 does not contain oxygen.
3. Phosphoric acid: One of the chemical components of DNA molecule is phosphoric acid. Its molecular symbol is H3PO4. It contains one divalent oxygen atom and three monovalent hydroxyl groups. Oxygen and hydroxyl groups combine with a pentavalent phosphorus atom to form phosphoric acid.