Structural Features of RNA Nucleotides
Ribonucleotides are the monomers of the RNA molecule. The carbohydrate component (pentose) is always ribose. The structure of these molecules is described through sequential complexity: from a free nitrogenous base to a nucleoside, and then to a complete nucleotide.
RNA includes the following components:
- Adenine (code A). Combining with ribose, it forms the nucleoside adenosine. The complete nucleotide is called adenosine monophosphate (AMP).
- Guanine (code G). The corresponding nucleoside is called guanosine, and the nucleotide is guanosine monophosphate (GMP).
- Uracil (code U). This RNA-specific base forms the nucleoside uridine. In its phosphorylated form, it is uridine monophosphate (UMP).
- Cytosine (code C). Forms the nucleoside cytidine, which exists within the nucleic acid as cytidine monophosphate (CMP).
Thus, the nomenclature of ribonucleotides is based on the names of their nitrogenous bases with the addition of the monophosphate group designation.
Specifics of DNA Nucleotides
Deoxyribonucleotides serve as the building blocks for DNA. The main chemical difference in this group lies in the carbohydrate residue—here, deoxyribose is present. This is reflected in the nomenclature: the prefix "deoxy-" (or the abbreviation "d-") is added to all nucleoside and nucleotide names.
The list of DNA nucleotides includes:
- Adenine (code A). Nucleoside: d-adenosine. Nucleotide: deoxyadenosine monophosphate (dAMP).
- Guanine (code G). Nucleoside: d-guanosine. Nucleotide: deoxyguanosine monophosphate (dGMP).
- Cytosine (code C). Nucleoside: d-cytidine. Nucleotide: deoxycytidine monophosphate (dCMP).
- Thymine (code T). This base is unique to DNA. It forms the nucleoside d-thymidine and the nucleotide deoxythymidine monophosphate (dTMP).
It is important to note that the letter codes (A, G, C, T) remain unchanged and are used internationally to designate base sequences.
Principles of Nomenclature
The naming system for nucleotides is based on a clear hierarchy of components. The foundation is the name of the nitrogenous base (e.g., adenine or uracil).
When a nitrogenous base binds to a sugar molecule (ribose or deoxyribose), a nucleoside is formed. Nucleoside names typically have the suffix -idine (uridine, cytidine) or -osine (adenosine, guanosine). If the carbohydrate is deoxyribose, the prefix d- is placed at the beginning of the name (e.g., d-guanosine).
Addition of a phosphate group turns the nucleoside into a nucleotide. In the full name, this is reflected by adding the word "monophosphate". Three- or four-letter abbreviations are formed: AMP, CMP, dGMP, dTMP. This logic makes it possible to accurately determine the structure of a molecule from its name.