NUCLEOSIDES, NUCLEOTIDES AND THEIR EXAMPLES

Nucleosides are organic molecules composed of a nitrogenous base and a five-carbon sugar, either ribose or deoxyribose. They are the building blocks of nucleic acids, such as DNA and RNA.

Nucleotides, on the other hand, are molecules consisting of a nucleoside linked to a phosphate group. They serve as the monomeric units of nucleic acids and play crucial roles in various cellular processes.

Examples of Nucleosides and Nucleotides:

1. Adenosine: Adenosine is a nucleoside composed of adenine and ribose. It is a component of both RNA and ATP (adenosine triphosphate), a molecule that serves as the primary energy carrier in cells.
2. Cytidine: Cytidine is a nucleoside containing cytosine and ribose. It is found in RNA and plays essential roles in protein synthesis.
3. Deoxythymidine: Also known as thymidine, this nucleoside consists of thymine and deoxyribose. It is a component of DNA and contributes to the genetic information storage in cells.
4. Adenosine Monophosphate (AMP): AMP is a nucleotide that contains adenosine linked to a single phosphate group. It participates in cellular energy transfer processes and serves as a substrate for various enzymatic reactions.
5. Cytidine Triphosphate (CTP): CTP is a nucleotide comprising cytidine linked to three phosphate groups. It plays crucial roles in RNA synthesis and serves as a precursor for the synthesis of complex lipids.
6. Deoxyadenosine Triphosphate (dATP): This nucleotide is involved in DNA synthesis and repair processes, providing the necessary building blocks for DNA replication.

Purines and Pyrimidines Nitrogenous Bases:

Purines and pyrimidines are two categories of nitrogenous bases that are fundamental components of nucleosides, nucleotides, DNA, and RNA.

1) Purines:

• Purines are heterocyclic aromatic organic compounds that consist of a six-membered ring fused to a five-membered ring.
• The two primary purines found in nucleic acids are adenine (A) and guanine (G).
• Adenine pairs with thymine (in DNA) or uracil (in RNA), while guanine pairs with cytosine.

2) Pyrimidines:

• Pyrimidines are also heterocyclic aromatic organic compounds but consist of only a six-membered ring structure.
• The three main pyrimidines present in nucleic acids are cytosine (C), thymine (T) – found in DNA, or uracil (U) – found in RNA.
• Cytosine forms hydrogen bonds with guanine, while thymine pairs with adenine in DNA. In RNA, uracil replaces thymine and pairs with adenine.

Understanding the structures and functions of nucleosides, nucleotides, purines, and pyrimidines is essential for comprehending the molecular basis of genetics, biochemistry, and cellular biology.