<unk> s are glycosylamines made by attaching a nucleobase (often referred to simply as base) to a ribose or deoxyribose ring. Examples of these include cytidine, uridine, adenosine, guanosine, thymidine and inosine. In short, a<unk>  is a base linked to sugar.<unk> s can be phosphorylated by specific kinases in the cell, producing<unk> s, which are the molecular building blocks of DNA and RNA.<unk> s are produced as the second step in nucleic acid digestion, whereby nucleotidases break down<unk> s (such as the thymine<unk>  into<unk> s (such as thymidine) and phosphate. The<unk> s, in turn, are subsequently broken down
in the lumen of the digestive system by<unk> ses into nitrogenous bases and ribose (or deoxyribose), and
inside the cell by<unk>  phosphorylases into nitrogenous bases, and ribose-1-phosphate (or deoxyribose-1-phosphate).<unk> s can be produced by combining nucleobases with deoxyribose rings as well.<unk> s differ from<unk> s 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.
In medicine several<unk>  analogues are used as antiviral or anticancer agents. The viral polymerase incorporates these compounds with non-canon bases. These compounds are activated in the cells by being converted into<unk> s, they are administered as<unk> s since charged<unk> s cannot easily cross cell membranes.
In molecular biology several analogues of the sugar back bone exist. Due to the low stability of RNA, which is prone to hydrolysis, several more stable alternative<unk> /nucleotide analogues are used which correctly bind to RNA. This is achieved by using a different backbone sugar. These analogues includ LNA, morpholino, PNA.
In sequencing dideoxynucleotides are used. These<unk> s posses a non-canon sugar, dideoxyribose which lacks 3' hydroxyl group (which accepts the phosphate) and therefore cannot bond with the next base, terminating the chain as DNA polymerases mistake it for a regular deoxyribonucleotide.
Nucleoside
Nucleic acid
Polyphosphate
Phospholipid
Glycolipid
Amino acid
Biopolymer
Polycyclic compound