A nucleotide is composed of three main parts: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group.
Parts of a Nucleotide
- Nitrogenous Base: This base contains nitrogen and acts as the information-coding part. In DNA, the bases are adenine (A), guanine (G), cytosine (C), and thymine (T). In RNA, uracil (U) replaces thymine. These bases are classified as purines (adenine and guanine) with two rings, and pyrimidines (cytosine, thymine, and uracil) with one ring.
- Pentose Sugar: This is a five-carbon sugar that forms the central framework of the nucleotide. In DNA, the sugar is deoxyribose, which lacks an oxygen atom at the 2' carbon making DNA more stable. In RNA, the sugar is ribose, which has a hydroxyl group at the 2' carbon, making it more reactive.
- Phosphate Group: The phosphate is attached to the 5' carbon of the sugar and links nucleotides together by forming phosphodiester bonds, creating a sugar-phosphate backbone. This group also gives nucleic acids their acidic nature and negative charge.
These three parts together form a nucleotide, which is the basic building block of nucleic acids like DNA and RNA.
