“Purine and pyrimidines are aromatic molecules involved in manufacturing the nucleic acid via hydrogen bonding.”


Both purines and pyrimidines are similar to the organic structure pyridine, however, the purines contain one hexose and one pentose ring while the pyrimidine contains a single hexo-cyclic ring. 

Purines and pyrimidines both are made up of the aromatic ring having carbon and nitrogen in it. 

Purines-adenine and guanine and pyrimidine-thymine, cytosine and uracil are involved in making nucleic acids- DNA and RNA.

Purines and pyrimidines are an important ingredient of the DNA along with the phosphate and the pentose sugar. 

Interestingly, purines and pyrimidines constructs nucleotides as well as nucleosides. The polynucleotide chain is known as DNA. 

By forming hydrogen bonds between opposite bases and phosphodiester bonds with the adjacent bases it creates the double-stranded structure of DNA. 

Pyrimidine bases- cytosine, thymine and uracil- elements of nucleic acid.

Differences between purines and pyrimidines: 

Structurally, the purines are made up of the two aromatic rings while the pyrimidines are made up of a single aromatic ring. 

In addition to this, the purines contain four different nitrogen atoms while the pyrimidines contain two nitrogen molecules in the ring. 

Due to these structural variations, the purines are bigger in size and shape as compared with the pyrimidines. 

The overall chemical formula of the purine is C5H4N4 while the chemical formula of the pyrimidine is C4H4N2

The chemical formula of individual purines and pyrimidines are given in the table below, 

Nitrogenous base Chemical formula
Purine:
Adenine C5H5N5
Guanine C5H4N5O
Pyrimidine:
Cytosine C4H4N2O2
Thymine C5H6N2O2
Uracil C4H4N2O2

One of the important properties of purine is its solubility in water. Purine is water-soluble while the pyrimidines are miscible (insoluble) in water. 

The biosynthesis of purine occurs in the liver, contrary, the biosynthesis of pyrimidine occurs in various tissues.

The catabolic product of the purine is uric acid while the catabolic end product of the pyrimidine is ammonia, beta-amino acids and carbon dioxide. 

Purine bases- Adenine and guanine- elements of nucleic acid.

Due to the structural complexity of the purine, the melting point of the purine is higher. 

“Note: the melting point is the temperature at which the molecule melts or dissolve.”  

The melting temperature of purine is 214°C (417°F) while the melting temperature of pyrimidine is 22°C (72°F). 

The molecular mass of the purine is 120.115 g/mol while the molecular mass of the pyrimidine is 80.08 g/mol. 

The purines are important biomolecule of the vitamin biosynthesis. 

While both purines and pyrimidines are used in DNA and RNA synthesis, energy storage, protein and starch synthesis, cell signalling and enzyme regulation. 

Read more:

DNA vs RNA: Differences And Similarities.

Summary of the article: 

Characteristic  Purine  Pyrimidine 
Bases  Adenine, Guanine  Cytosine, thymine and uracil 
Structure  Two rings (one is a pyrimidine)  Single ring 
Formula  C5H4N4 C4H4N2
Nucleic acid  DNA and RNA both  Thymine and cytosine in DNA while uracil and cytosine in RNA. 
Biosynthesis  Liver  Various tissues 
End product  Uric acid  Beta-amino acid, carbon dioxide and ammonia. 
Function  Vitamine, drug, nucleic acid, cell signalling, enzyme regulation.  Drug, nucleic acid, cell signalling, enzyme regulation. 

Related reads:

Nucleotides Vs Nucleosides.