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

The Molecules We Are Made Of
Nucleic Acids
Nomenclature and Abbreviations

The purine and pyrimidine cyclic Components of nucleic acids are simply referred to as bases, although some of them actually lack basic properties. The N-Glycosides (or N-glycosyl derivatives) of these bases containing ribose or deoxyribose are called nucleosides, and the phosphate esters of nucleosides are called NUCLEOTIDES. Related biochemical compounds that are not part of DNA or RNA are named similarly.

The nomenclature of Nucleosides and Nucleotides relates to the names of the bases in a somewhat non-intuitive way. (The names of the major nucleotides that make up Nucleic Acids are listed in Table 2-5.)

Class="center">

FIG. 2-20. Formation of a nucleotide from a pyrimidine base, D-ribose, and a phosphate ion. The reaction is shown to release Water molecules. Note that the carbon atoms of the bases are numbered from 1 to 6 or from 1 to 9 (Fig. 2-19), while the sugar carbon atoms are numbered from 1' to 5'.

FIG. 2-21. Schematic planar representation of the Watson-Crick Introduction/20.html">DNA Structure.

This is particularly true for hypoxanthine, which is formed by replacing the —NH2 group of adenine with an —OH group, followed by tautomerization of the oxypurine group

into the form

Table 2-5 Names of pyrimidine and purine bases, nucleosides, 5'-nucleotides, and their Abbreviations

A. RNA nucleotide unitsa

Bases

Uracil

Ura(U)

Cytosine

Cyt (C)

Adenine

Ade(A)

Guanine

Gua (G)

Nucleosides

Uridine Urd

Cytidine Cyd

Adenosine Ado

Guanosine Guo

5'-nucleotides

Uridine-5'-phosphate or 5'-uridylic acid Urd-5'-P or UMP

Cytidine-5'-phosphate or 5'-cytidylic acid

Cyd-5'-P or CMP

Adenosine-5'-phosphate or 5'-adenylic acid

Ado-5'-P or AMP

Guanosine-5'-phosphate or 5'-guanylic acid

Guo-5'-P or GMP

B. DNA nucleotide units

DNA contains 2-deoxyribose instead of ribose; therefore, the corresponding DNA nucleosides and nucleotides are called deoxyadenosine (dAdo), deoxyadenosine-5'-phosphate (dAMP), etc.

Thymine (Thy) is present in DNA instead of uracil. In this case, the deoxyribose derivatives are thymidine (dThd) and thymidine-5'-phosphate. The ribose derivatives of thymine are the nucleoside ribosylthymidine (Thd) and ribosylthymidine-5'-phosphate (Thd-5'-P).

a Isomers of 5'-nucleotides in which the phosphate is attached to the oxygen at C-3' are called 3'-nucleotides. Such isomers occur quite frequently, and confusion in this regard should be avoided. The simple abbreviations UMP, CMP, AMP, and GMP always refer to 5'-nucleotides.

The nucleoside composed of hypoxanthine and ribose is called inosine (I), and the corresponding nucleotide is inosinic acid.

In commonly used shorthand formulas for nucleic acids, the sugars are depicted as vertical lines. Symbols corresponding to specific bases A, C, U, T, and G, or Purines (Pu) and Pyrimidines (Py), are placed directly above these lines; 3'—5' phosphodiester bonds are represented by slanted lines with the letter P in the middle:

The structural formula of the same polynucleotide can be written even more concisely:

By convention, the 5'-end of a nucleotide in such formulas is placed on the left.



Last update: 06/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.