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Difference Between Nucleotide and Nucleoside

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MVSAT 2024

It is extremely essential to understand the key differences between a nucleotide and a nucleoside to differentiate between the two. While both are essentially the foundation of nucleic acid, the molecular composition is highly varying, with nucleotides containing sugar, base, and a phosphate group, and nucleosides containing only sugar and a base. Additionally, a nucleotide occurs before the formation of DNA and RNA, but a nucleoside occurs before the formation of a nucleotide.


A nucleotide is an organic molecule that serves as the foundation for RNA and DNA. Nucleotides also have roles that are linked to enzyme processes, cell signalling, and metabolism. A phosphate group, a nitrogenous base, and a 5-carbon sugar are all present in the nucleotide.

Compounds consisting of a nitrogenous base and a phosphate group which is attached to a pentose sugar, which can be either deoxyribose or ribose, called as nucleotides. The pentose sugar with 5’ carbon can have anywhere between one and three phosphate groups. The nitrogenous base, however, can be either pyrimidine or a purine. While guanine and adenine are known to be purine bases, thymine, uracil, and cytosine are pyrimidine bases.

The table below shows examples of nucleotides that correspond to their nitrogenous bases.

Nitrogenous Bases

Corresponding Examples




AMP, ADP, ATP, dAMP, dADP, dATP, and ddATP


CMP, CDP, CTP, dCMP, dCDP, dCTP, and ddCTP


TMP, TDP, TTP, dTMP, dTDP, dTTP, and ddTTP

Nucleotides are widely used as energy sources- – while ATP has biochemical usage, GTP is where the energy source is derived during protein synthesis. In the endocrine system and the nervous system, there can be seen the involvement of cyclic AP in signal transduction. Dideoxynucleotides often help in sequencing for chain termination. Also, for the regulation of the gene expression, LNA, PNA, and morpholino are crucial for the sugar backbone in RNA.

Furthermore, each organism's genetic material is formed by a nucleotide within a certain chain. Outside of genetic information storage, they perform a variety of activities as energy-moving particles and messengers.

DNA and RNA vary in different particulars, DNA contains sugar deoxyribose whereas RNA has sugar ribose. Furthermore, a codon is a sequence of three nucleotides in DNA. A codon instructs cell proteins to link a certain protein to a DNA sequence.

A purine or pyrimidine nucleobase bound to a deoxyribose or pentose sugar ribose is referred to as a nucleoside. Furthermore, a glycosidic link connects an anomeric carbon to the purine's N9 in a nucleoside. Furthermore, rather than the N9 of purine, this attachment can be to the N1 of a pyrimidine.

Purine and pyrimidine are two different types of nucleotides. Purine is a nitrogen-containing ring with six members fused to an imidazole ring. Pyrimidine, on the other hand, only possesses a six-numbered nitrogen-containing ring.

Types of nucleotide

  1. Adenine: The nucleotide adenine is used as a base in adenosine triphosphate (ATP). Purines are one of two types of nitrogenous bases. Adenine belongs to the purine family. ATP allows for the storage of a large amount of energy in strong bonds.

  1. Guanine: Guanine, like adenine, is a purine nucleotide with two rings. In both DNA and RNA, it binds to cytosine. Guanine forms three hydrogen bonds with cytosine, as shown in the figure above. The cytosine–guanine bond is therefore slightly stronger than the thymine–adenine bond, which only has two hydrogen bonds.

  1. Cytosine: Pyrimidines are the other nucleotide class. Cytosine is like a single ring-shaped pyrimidine nucleotide. Cytosine tends to bind with both DNA and RNA. The nucleotide guanine forms a strong bond with the nucleotide adenine.

  1. Thymine: Thymine is a pyrimidine nucleotide with only one ring exactly like cytosine. In DNA, it forms a link with adenine. RNA does not contain thymine. It is the weaker of the two since it only forms two hydrogen bonds with adenine in DNA.

  1. Uracil: Uracil is a pyrimidine as well. Uracil is put where thymine would ordinarily be during DNA to RNA transcription. Though uracil has several specific advantages and downsides, the cause for this is unknown. Because uracil is short-lived and can break down into cytosine, most animals do not employ it in their DNA. However, because RNA is a short-lived molecule, uracil is the chosen nucleotide.


A nucleoside is any nucleotide that does not have a phosphate group but is bound to the 5’ carbon of the pentose sugar. A nucleotide always contains a nucleoside that binds the one to three phosphate groups.

A nucleoside can be classified as either a ribonucleoside or a deoxyribonucleoside based on the pentose sugar component. A ribonucleoside is a nucleoside that contains the ribose sugar component. Deoxyribonucleoside, on the other hand, is a nucleoside having  deoxyribose sugar.

Examples of nucleosides include cytidine, uridine, guanosine, inosine thymidine, and adenosine. A beta-glycosidic bond binds the 3’ position of the pentose sugar to the nitrogenous base.

Nucleosides are used as anticancer and antiviral agents.

Types of Nucleosides

  1. Adenosine: Adenosine is a purine nucleoside in which adenine is glycosidically linked to a ribose sugar. It is a structural component of key macromolecules like DNA and RNA that may be found in all living species. ATP, ADP, and AMP all contain it as a key molecular component. As a result, it plays a role in physiologic processes like energy transfer (e.g., ATP) and signal transduction (i.e., as cAMP). It also functions as an inhibitory neurotransmitter, which aids sleep.

  2. Guanosine: Guanosine is a purine nucleoside made up of guanine and ribose sugar. Through phosphorylation, it can be transformed to nucleotides such as guanosine monophosphate (GMP), cyclic guanosine monophosphate (cGMP), guanosine diphosphate (GDP), or guanosine triphosphate (GTP). Nucleic acid synthesis, protein synthesis, photosynthesis, muscular contraction, and intracellular transmission are just a few of the biochemical processes that these nucleotides are engaged in.

  3. Cytidine: Cytidine is a pyrimidine nucleoside with the cytosine sugar ribose linked to it. It may have antidepressant properties because it regulates glutamate cycling between neurons and glia.

  4. Uridine: Uridine is a ribonucleoside with a ribose ring and uracil attached. It's an odourless white powder that has a role in glucose metabolism.

Difference Between Nucleotide and Nucleoside



Nucleotides are built of a nitrogenous base, a sugar, and a phosphate group when it comes to chemical composition. 

Nucleosides are built of a nitrogenous base and a sugar, however, without the phosphate group when it comes to chemical composition. 

To this day, malfunctioning nucleotides are one of the major reasons behind cancer. 

Nucleosides, on the other hand, are used for medicinal purposes, mostly as anti-cancer agents and against various viruses. 

Nucleotide = Sugar + Base + Phosphate

Nucleoside = Sugar + Base

Common examples of nucleotides include adenosine, cytidine, guanosine, uridine, thymidine, and inosine with the inclusion of phosphate groups. 

Examples of nucleotides also include adenosine, cytidine, guanosine, uridine, thymidine, and inosine;, however, there is no presence of phosphate groups. 

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FAQs on Difference Between Nucleotide and Nucleoside

1. What is nucleotide and nucleoside?

The basic building block of a specific acid, the nucleic acid, is referred to as a nucleotide. This clearly demonstrates the distinction between nucleotide and nucleic acid. A nucleotide also contains a sugar molecule bound to a phosphate group, as well as a nitrogen-containing base.

The difference between nucleotide and nucleoside is that nucleoside refers to a component of a nucleotide. Additionally, a nucleotide is the monomeric unit of nucleic acid, which includes DNA and RNA. Furthermore, a nucleobase is a nitrogen-containing molecule that, when attached to deoxyribose or a five-carbon sugar ribose, can result in the creation of nucleosides.

2. What is the function of nucleotide?

A nucleotide can serve a variety of tasks in addition to being the basic unit of genetic material for all living organisms. A base in another molecule, such as adenosine triphosphate (ATP), the cell's main energy molecule, can be a nucleotide. They're also found in coenzymes like NAD and NADP, which are derived from ADP and are involved in a variety of chemical reactions in metabolism. Another nucleotide-containing molecule is cyclic AMP (cAMP), a messenger molecule involved in a variety of functions, including metabolic regulation and the delivery of chemical signals to cells. Nucleotides are not only the components of life but also the components of many different chemicals that make life possible.

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