What Are Nucleotides?
Nucleotides are organic molecules that are composed of a sugar, a nitrogenous base and a phosphate group. These molecules are the building blocks of DNA and RNA, the structures that control all the hereditary characteristics of our body. Let us look at the three main parts of a nucleotide.
Three Parts of Nucleotide
- Sugar
- Nitrogenous Base
- Phosphate Group
The sugar component of the nucleotides is a five-carbon sugar. Deoxyribose or 2-deoxyribose is the five-carbon sugar that is found in DNA, whereas ribose is found in RNA. The primary difference between the two sugars is the replacement of hydroxyl group by hydrogen at the 2’ position in deoxyribose.
The sugars are attached to the nitrogenous bases at the 1’ carbon and to the phosphate group at the 5’ carbon and 3’ carbon of the preceding sugar unit. The absence of the oxygen atom in the deoxyribose sugar is advantageous as it provides better flexibility and promotes double helix formation of the DNA structure.
Nitrogenous bases, as the name suggests are nitrogen containing basic compounds. There are a total of five bases found in the DNA and RNA world, namely – Adenine (A), Cytosine (C), Guanine (G), Thymine (T) and Uracil (U).
A, T, C and G are found in DNA molecules whereas the uracil base is found in RNA molecules in place of the thymine.
The phosphate group is attached to the sugar by a phosphodiester bond forming the backbone of the DNA. The phosphate group forms the bond by attaching at the 5’ carbon of sugar and with the free hydroxyl group on the 3’ carbon of another sugar. This way, the polynucleotide structure of the DNA keeps growing in the direction of 5’ to 3’.
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