Nucleosides and Nucleotides

The major group of biochemical molecules, nucleosides and nucleotides, are required for various biological tasks in humans. This includes retaining and conveying genetic information, storing energy, and acting as signalling molecules. Purines, which comprise adenosine and guanine, and pyrimidines, including thymidine, cytosine, and uracil, are the two major families of these molecules. These molecules’ distinct shapes and interactions serve as the building blocks of RNA and DNA molecules, allowing gene replication and protein synthesis.

What are Nucleosides and Nucleotides?

• Nucleosides are structural subunits of nucleic acids which control heredity in all living cells. They are composed of a sugar molecule (ribose or deoxyribose) linked to a nitrogen-containing organic ring compound which is either a pyrimidine (cytosine, uracil, or thymine) or a purine in the most significant nucleosides (adenine or guanine).
• A nucleotide is an organic molecule with a nitrogenous base, pentose sugar, and phosphate as its basic components.
• Polynucleotides, such as DNA and RNA, comprise a chain of nucleotide monomers with various nitrogenous bases.
• Nucleotides are required for metabolic and physiological processes to occur.

Structure of Nucleosides and Nucleotides 

• Structure of Nucleosides

A nucleoside comprises simply a nitrogenous base and a five-carbon sugar, while a nucleotide comprises a nucleobase, a five-carbon sugar, and one or more phosphate groups. The base is connected to ribose or deoxyribose via a beta-glycosidic bond at the 1’ position in a nucleoside. Cytidine, uridine, adenosine, guanosine, thymidine, and inosine are examples of nucleosides.

• Structure of Nucleotides

A nitrogen-containing base, a five-carbon sugar (pentose), and at least one phosphate group make up a single nucleotide. A nucleotide is also known as a “nucleoside phosphate” when all three are linked together. Individual phosphate molecules repeatedly connect the sugar-ring molecules in two neighbouring nucleotide monomers, resulting in a lengthy chain of nucleotide monomers. Singular cyclic nucleotides are created when the phosphate group is bonded twice to the same sugar molecule, i.e., at the corners of the sugar hydroxyl groups, unlike nucleic acid nucleotides.

Difference between Nucleosides and Nucleotides

Functions of Nucleosides and Nucleotides 

• Functions of Nucleosides

  • Nucleosides are components of nucleotides. They are nucleotide precursors. The nucleotide, the backbone of DNA, is formed when a phosphate group is bonded to the nucleoside.
  • Signalling molecules are also nucleoside molecules.
  • Nucleosides with minor bases or altered nitrogen bases regulate and safeguard genetic information.
  • Malignancies, tumours, and viral infections have all been treated with nucleoside analogues. This is accomplished by altering the purine and pyrimidine bases.
  • Some nucleoside analogues are used in the treatment of HIV infection. This treatment involves the administration of lamivudine.
  • Nucleoside transporters are essential for nucleoside transfer across membranes.
  • These are classified as either concentrated or equilibrative. Antiviral and anticancer medicines are transported across membranes with the help of these transporters.

• Functions of Nucleotides

  • Because nucleotides are the building blocks of nucleic acids, the chemicals control all hereditary features. Hence, they are essential to living creatures.
  • Nucleotides are linked by 3′,5′-phosphodiester bridges to form polynucleotides. The genetic message is encoded in the polynucleotide chain’s base sequence.
  • In cellular metabolism, nucleotides have several activities. In metabolic exchanges, they are the energy currency.
  • They serve as crucial chemical linkages in cells’ responses to hormones and other external stimuli.
  • Every protein’s structure, and thus every biomolecule and cellular component, results from information encoded in the nucleotide sequence of a cell’s nucleic acids.
  • Providing energy reserves for future phosphate transfer reactions. ATP is primarily responsible for these reactions.
  • As neurotransmitters and ligands for signal receptors. Adenosine is an inhibitory neurotransmitter, and ATP influences synaptic neurotransmission in central and peripheral nervous systems. ADP is a key stimulator of platelet activities, which regulates blood coagulation.

Conclusion

In research, knowing the distinction between nucleotide and nucleoside is essential. A nucleotide comprises sugar, a nitrogenous base, and one to three phosphate groups. On the other hand, a nucleoside is a nitrogenous base with a covalent bond to sugar but no phosphate group.