Nucleosides: Nucleoside contains only two basic components of nucleic acids (a pentose sugar and a nitrogenous base). During their formation, 1- position of pyrimidine or 9 – position of purine moiety is linked to C1 of sugar (ribose or deoxyribose) by b – linkage.
General structure of a nucleoside
Depending upon the type of sugar present, nucleosides are of two types:
(i) Ribonucleosides and
(ii) Deoxyribonucleosides
Nucleotides: Nucleotides contains all the three basic components of nucleic acids. Nucleotides are nucleoside monophosphates.
They are of two types depending upon the type of sugar – Ribonucleotides and Deoxyribonucleotides. Nucleotide may be represented as follows.
| DNA | RNA | ||
| 1. | Sugar present in DNA is 2-deoxyribose. | 1. | Sugar is D-ribose. |
| 2. | It contains cytosine and thymine as pyrimidine. | 2. | It contains cytosine and uracil as pyrimidine. |
| 3. | It has double stranded a – helix structure. | 3. | It has single stranded a – helix. |
| 4. | DNA occurs in the nucleus of cell. | 4. | RNA occurs in cytoplasm of the cell. |
| 5. | Controls transmission of hereditary material. | 5. | It control the synthesis of proteins. |
