Nucleic acids are made up of three main components. These are-
1. Nitrogen Alkali: This alkali is formed by carbon, hydrogen, oxygen and nitrogen. It contains 15% 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, Cytosine and Uracil.
Nomenclature of Nitrogen Alkalies
Adenine and Thymine are named after Thymus. They were isolated from the thymus gland. Adeno means gond. Cytosine is named after cyto. Cyto means cell. Guanine comes from the Spanish word guano. Guano means the droppings of bats. Alkalies are usually denoted by the alphabet AGTCU. DNA molecules have the letters AGTC and RNA molecules have the letters AGCU.
2. Pentose Sugar: Five-carbon sugar (sugar) is called pentose sugar. Nucleic acids contain two types of pentose sugars. Ribose sugar and deoxyribose sugar.
(i) Ribose sugar: RNA molecule contains ribose sugar. It is a type of monosaccharide. Its 2nd carbon contains oxygen.
(ii) Deoxyribose sugar: DNA molecule contains deoxyribose sugar. It is a type of monosaccharide. Its 2nd carbon does not contain oxygen (deoxy = less of one oxygen) so named. That is why it is called 2-β-D deoxyribose sugar.
3. Phosphoric acid: One of the chemical components of chromosomes is phosphoric acid. It contains 10% phosphorus element. 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.
Nucleic acids are composed of carbon, hydrogen, oxygen, nitrogen and phosphorus. It contains 15% nitrogen and 10% phosphorus.