What is the monomer of nucleic acids?

The monomers of nucleic acids are nucleotides. Each nucleotide is composed of three parts:

1. A pentose sugar: This is a five-carbon sugar. In DNA, the sugar is deoxyribose; in RNA, it's ribose. The difference lies in the presence of a hydroxyl (-OH) group on the 2' carbon of ribose, which is absent in deoxyribose. This seemingly small difference has significant implications for the stability and function of the two nucleic acids.

2. A phosphate group: This is a negatively charged group (PO₄³⁻) that links nucleotides together to form the sugar-phosphate backbone of the nucleic acid chain. The phosphate group connects the 3' carbon of one sugar to the 5' carbon of the next sugar, creating a directional 5' to 3' chain.

3. A nitrogenous base: This is a nitrogen-containing ring structure. There are five main types of nitrogenous bases:

   • Adenine (A)
   • Guanine (G)
   • Cytosine (C)
   • Thymine (T) (found only in DNA)
   • Uracil (U) (found only in RNA)

The nitrogenous bases are categorized into two groups based on their structure:

• Purines: Adenine and Guanine (double-ring structures)
• Pyrimidines: Cytosine, Thymine, and Uracil (single-ring structures)

The sequence of nitrogenous bases along the nucleic acid chain determines the genetic information encoded within the molecule. The specific pairing of bases (A with T or U, and G with C) via hydrogen bonds is crucial for the double-helix structure of DNA and the various secondary structures of RNA.