Phosphodiester bond

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A phosphodiester bond occurs when exactly two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. An example is found in the linking of two [[Pentose|pentose ]](5 carbon sugar) rings to a [[Phosphate group|phosphate group]] by strong,&nbsp;[[Covalent|covalent]]&nbsp;[[Ester bond|ester bonds]]. Each ester bond is formed by a [[Condensation Reaction|condensation reaction]] in which water is lost. This bond is a key structural feature of the backbone of DNA and RNA and links the 3’ carbon of one nucleotide to the 5’ carbon of another to produce the strands of [[DNA|DNA and]] [[RNA|RNA]].
The phosphodiester bond links two [[Pentose|pentose ]](5 carbon sugar) to a [[Phosphate group|phosphate group]] by strong, [[Covalent|covalent]], [[Ester bond|ester bonds]]. The formation of these bonds is a [[Condensation Reaction|condensation reaction]] in which water is lost. This bond is a key structural feature of the backbone of DNA and RNA and links the 3’ carbon of one nucleotide to the 5’ carbon of another to produce the strands of [[DNA|DNA and]] [[RNA|RNA]].  
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= Phosphodiester Bond Formation  =
 
= Phosphodiester Bond Formation  =
  
In phosphodiester formation, the 1’ and 2’ [[Hydroxyl groups|hydroxyl ]](OH) groups of the phosphate molecule bind to the 3’ and 5’ carbons of the two independent pentose sugars. These are two condensation reactions so produce two molecules of water. The phosphate is then bonded to the sugars by two ester bonds, so is called a phosphodiester bond. This reaction is catalysed by [[Ligase|ligases]], such as [[Dna ligase|DNA ligase]] during DNA replication. <br>  
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In phosphodiester formation, two&nbsp;[[Hydroxyl groups|hydroxyl ]](OH) groups on the phosphate molecule bind to the 3’ and 5’ carbons on two independent pentose sugars. These are two condensation reactions, so two molecules of water are produced. The phosphate is then bonded to the sugars by two ester bonds, hence the nomenclature of phosphodiester bond. This reaction is catalysed by [[Ligase|ligases]], such as [[Dna ligase|DNA ligase]] during [[DNA_replication|DNA replication]]. <br>  
  
The mechanism for this reaction is given below.  
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A representation of the reaction is shown in the diagram below.  
  
[[Image:Phosphodiester formation mechanism.png|774x512px]]  
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[[Image:Phosphodiester formation mechanism.png|774x512px|Phosphodiester formation mechanism.png]]  
  
 
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= <br>Phosphodiester Bond Hydrolysis  =
 
= <br>Phosphodiester Bond Hydrolysis  =
  
In phosphodiester [[Hydrolysis|hydrolysis]], water dissociated into H<sup><sub>+</sub></sup>and OH<sup>-</sup>. The OH<sup>-</sup> acts as the [[Nucleophile|nucleophile in]] the [[Nucleophilic substitution|nucleophilic substitution]] reaction of hydrolysis. The reaction is catalysed by [[Phosphodiesterase|phosphodiesterase]].<br>The mechanism of this reaction is given below.  
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In phosphodiester [[Hydrolysis|hydrolysis]], water is dissociated into H<sup><sub>+&nbsp;</sub></sup>and OH<sup>-</sup>. The OH<sup>-</sup> acts as a&nbsp;[[Nucleophile|nucleophile]] in the reaction. The reaction is catalysed by [[Phosphodiesterase|phosphodiesterase]].<br>The mechanism of this reaction is given below.  
  
[[Image:Phosphodiester hydrolysis mechanism.png|992x208px]]<br><br>
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[[Image:Phosphodiester hydrolysis mechanism.png|992x208px|Phosphodiester hydrolysis mechanism.png]]<br><br>

Latest revision as of 15:35, 30 November 2012

A phosphodiester bond occurs when exactly two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. An example is found in the linking of two pentose (5 carbon sugar) rings to a phosphate group by strong, covalent ester bonds. Each ester bond is formed by a condensation reaction in which water is lost. This bond is a key structural feature of the backbone of DNA and RNA and links the 3’ carbon of one nucleotide to the 5’ carbon of another to produce the strands of DNA and RNA.

Phosphodiester Bond Formation

In phosphodiester formation, two hydroxyl (OH) groups on the phosphate molecule bind to the 3’ and 5’ carbons on two independent pentose sugars. These are two condensation reactions, so two molecules of water are produced. The phosphate is then bonded to the sugars by two ester bonds, hence the nomenclature of phosphodiester bond. This reaction is catalysed by ligases, such as DNA ligase during DNA replication.

A representation of the reaction is shown in the diagram below.

Phosphodiester formation mechanism.png



Phosphodiester Bond Hydrolysis

In phosphodiester hydrolysis, water is dissociated into Hand OH-. The OH- acts as a nucleophile in the reaction. The reaction is catalysed by phosphodiesterase.
The mechanism of this reaction is given below.

Phosphodiester hydrolysis mechanism.png

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