Biochemistry - The Chemical Reactions of Living Cells, Volume 1 - D. Metzler 1980

The Molecules We Are Made Of
Nucleic Acids

Nucleic Acids — DNA and RNA — are polynucleotides. Their monomer units (NUCLEOTIDES) in turn consist of three parts:

1. A purine or pyrimidine base (their structural formulas are shown in Fig. 2-19).

2. A sugar — D-ribose or D-2-deoxyribose.

3. Phosphoric acid.

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FIG. 2-19. Structural formulas of pyrimidine and purine bases. Monographs and reference books usually depict the rings in a different orientation, with the C-5 atom of the pyrimidine ring and the C-8 atom of the purine positioned on the right. We have chosen this particular orientation to ensure consistency between this figure and Fig. 2-20.

These components join together with the release of two Water molecules (Fig. 2-20). The nucleotides are linked by phosphodiester bonds formed between the 5'-hydroxyl of one nucleotide sugar and the 3'-hydroxyl of another [equation (2-11)]. The Structure of a pair of short polynucleotide chains is illustrated in Fig. 2-21.



Last update: 06/08/2026

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