Editing Cyclic nucleotide (section)

===Structure===
[[Image:CGMP.png|thumb|[[Cyclic guanosine monophosphate]].  The cyclic portion refers to the two single bonds between the [[phosphate]] group and the [[ribose]]]]
The two most well-studied cyclic nucleotides are cyclic AMP (cAMP) and cyclic GMP (cGMP), while cyclic CMP (cCMP) and cyclic UMP (cUMP) are less understood.  cAMP is 3’5’-cyclic adenosine monophosphate, cGMP is 3’5’-cyclic guanosine monophosphate, cCMP is cytidine 3',5'-monophosphate, and cUMP is uridine 3',5'-cyclic phosphate.<ref>{{Cite journal|last=Seifert |first= R.|year=2015 |title=cCMP and cUMP: emerging second messengers |journal= Trends in Biochemical Sciences |volume= 40|issue= 1 |pages= 8–15 |url= https://doi.org/10.1016/j.tibs.2014.10.008 |doi=10.1016/j.tibs.2014.10.008|pmid= 25435399}}
</ref><ref name="Gomelsky">{{cite journal|last=Gomelsky|first=Mark|title=cAMP, c-di-GMP, c-di-AMP, and now cGMP: bacteria use them all!|doi=10.1111/j.1365-2958.2010.07514.x|pmid=21255104|volume=79|issue=3|journal=Molecular Microbiology|pages=562–565|pmc=3079424|year=2011}}</ref>

Each cyclic nucleotide has three components. It contains a nitrogenous base (meaning it contains nitrogen): for example, [[adenine]] in cAMP and [[guanine]] in cGMP. It also contains a sugar, specifically the five-[[carbon]] ribose. And finally, a cyclic nucleotide contains a phosphate.  A double-ring [[purine]] is the nitrogenous base for cAMP and cGMP, while cytosine, [[thymine]], and [[uracil]] each have a single-ring nitrogenous base ([[pyrimidine]]).

These three components are connected so that the nitrogenous base is attached to the first carbon of ribose (1’ carbon), and the phosphate group is attached to the 5’ carbon of ribose. While all nucleotides have this structure, the phosphate group makes a second connection to the ribose ring at the 3’ carbon in cyclic nucleotides.  Because the phosphate group has two separate bonds to the ribose sugar, it forms a cyclic ring.<ref>{{cite book|last=Nelson|first=David|title=Lehninger Principles of Biochemistry|year=2008|publisher=W.H. Freeman and Company|location=New York, NY|isbn=978-0-7167-7108-1|edition=Fifth|author2=Michael Cox|url-access=registration|url=https://archive.org/details/lehningerprincip00lehn_1}}</ref>

The [[atom]] numbering convention is used to identify the carbons and nitrogens within a cyclic nucleotide.  In the pentose, the carbon closest to the [[carbonyl]] group is labeled C-1.  When a pentose is connected to a nitrogenous base, carbon atom numbering is distinguished with a prime (') notation, which differentiates these carbons from the atom numbering of the nitrogenous base.<ref>{{cite web|title=Nucleotide Numbering|url=http://www.tulane.edu/~biochem/nolan/lectures/rna/frames/nucs.htm|publisher=Tulane University|access-date=9 May 2013}}</ref>

Therefore, for cAMP, 3’5’-cyclic adenosine monophosphate indicates that a single phosphate group forms a cyclic structure with the ribose group at its 3’ and 5’ carbons, while the ribose group is also attached to adenosine (this bond is understood to be at the 1’ position of the ribose).