Nucleoside

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Nitrogenous base	Nucleoside	Deoxynucleoside
Image:Adenine chemical structure.png Adenine	Image:A chemical structure.png Adenosine A	Image:DA chemical structure.png Deoxyadenosine dA
Image:Guanine chemical structure.png Guanine	Image:G chemical structure.png Guanosine G	Image:DG chemical structure.png Deoxyguanosine dG
Image:Thymine chemical structure.png Thymine	Image:M5U chemical structure.png 5-Methyluridine m⁵U	Image:DT chemical structure.png Deoxythymidine dT
Image:Uracil chemical structure.png Uracil	Image:U chemical structure.png Uridine U	Image:DU chemical structure.png Deoxyuridine dU
Image:Cytosine chemical structure.png Cytosine	Image:C chemical structure.png Cytidine C	Image:DC chemical structure.png Deoxycytidine dC

Nucleosides are glycosylamines made by attaching a nucleobase (often referred to simply as bases) to a ribose or deoxyribose ring. Examples of these include cytidine, uridine, adenosine, guanosine, thymidine and inosine.

Nucleosides can be phosphorylated by specific kinases in the cell, producing nucleotides, which are the molecular building blocks of DNA and RNA.

Nucleosides are produced as the second step in nucleic acid digestion, when nucleotidases break down nucleotides (such as the thymine nucleotide) into nucleosides (such as thymidine) and phosphate. The nucleosides, in turn, are subsequently broken down:

- in the lumen of the digestive system by nucleosidases into nitrogenous bases and ribose (or deoxyribose).

- inside the cell by nucleoside phosphorylases into nitrogenous bases, and ribose-1-phosphate (or deoxyribose-1-phosphate).

Nucleosides differ from nucleotides by having a hydroxyl group attached to carbon number 5 (the one that isn't in the ring) of the ribose, rather than one or more phosphate groups.

[edit] See also

Nucleic acids and oligonucleotides edit
Nucleobases:	Adenine \| Thymine \| Uracil \| Guanine \| Cytosine \| Purine \| Pyrimidine
Nucleosides:	Adenosine \| Uridine \| Guanosine \| Cytidine \| Deoxyadenosine \| Thymidine \| Deoxyguanosine \| Deoxycytidine
Nucleotides:	AMP \| UMP \| GMP \| CMP \| ADP \| UDP \| GDP \| CDP \| ATP \| UTP \| GTP \| CTP \| cAMP \| cADPR \| cGMP
Deoxynucleotides:	dAMP \| TMP \| dGMP \| dCMP \| dADP \| TDP \| dGDP \| dCDP \| dATP \| TTP \| dGTP \| dCTP
Ribonucleic acids:	RNA \| mRNA \| tRNA \| rRNA \| ncRNA \| sgRNA \| shRNA \| siRNA \| snRNA \| miRNA \| snoRNA \| LNA
Deoxyribonucleic acids:	DNA \| mtDNA \| cDNA \| plasmid \| Cosmid \| BAC \| YAC \| HAC
Analogues of nucleic acids:	GNA \| PNA \| TNA\| morpholino
←Amino acids	Major families of biochemicals	Carbohydrates→