Purine vs. Pyrimidine — What's the Difference?
By Fiza Rafique & Maham Liaqat — Updated on May 16, 2024
Purines and pyrimidines are nitrogenous bases found in nucleotides; purines (adenine and guanine) have a double-ring structure, while pyrimidines (cytosine, thymine, and uracil) have a single-ring structure.
Difference Between Purine and Pyrimidine
Table of Contents
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Key Differences
Purines are one of the two types of nitrogenous bases found in nucleotides, the building blocks of DNA and RNA. They have a characteristic double-ring structure composed of a six-membered and a five-membered nitrogen-containing ring fused together. Pyrimidines, on the other hand, are characterized by a single-ring structure composed of a six-membered nitrogen-containing ring.
While purines are larger molecules due to their double-ring structure, pyrimidines are smaller with a single ring. This size difference is crucial for the complementary base pairing mechanism in nucleic acids, ensuring the DNA double helix has a consistent width.
Both purines and pyrimidines are essential for the storage and transmission of genetic information. Their specific pairing (A-T or A-U, and G-C) facilitates the accurate replication of DNA and the proper transcription of RNA, which is vital for protein synthesis and cell function.
Purines and pyrimidines also play roles beyond nucleic acids. For example, ATP (adenosine triphosphate), a purine nucleotide, is crucial for energy transfer in cells, and cyclic AMP (cAMP), another purine derivative, is important in cell signaling.
Comparison Chart
Structure
Double-ring (six-membered + five-membered)
Single-ring (six-membered)
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Bases in DNA/RNA
Adenine (A), Guanine (G)
Cytosine (C), Thymine (T), Uracil (U)
Pairing
A pairs with T (DNA) or U (RNA), G pairs with C
C pairs with G, T pairs with A (DNA), U pairs with A (RNA)
Size
Larger
Smaller
Role
Structural components of DNA/RNA, energy transfer (ATP)
Structural components of DNA/RNA
Additional Function
Involved in energy transfer and signaling (e.g., ATP, cAMP)
Primarily structural in nucleic acids
Compare with Definitions
Purine
Includes adenine (A) and guanine (G).
Guanine (G) pairs with cytosine in DNA and RNA.
Pyrimidine
A nitrogenous base with a single-ring structure found in DNA and RNA.
Thymine (T) is a pyrimidine that pairs with adenine in DNA.
Purine
Involved in cell signaling (cAMP).
Cyclic AMP (cAMP) is a purine nucleotide important in various signaling pathways.
Pyrimidine
Includes cytosine (C), thymine (T), and uracil (U).
Uracil (U) replaces thymine in RNA and pairs with adenine.
Purine
A nitrogenous base with a double-ring structure found in DNA and RNA.
Adenine (A) is a purine that pairs with thymine in DNA.
Pyrimidine
Forms specific pairs in DNA and RNA.
Cytosine (C) pairs with guanine in both DNA and RNA.
Purine
Larger due to the fused double-ring system.
The larger size of purines allows them to pair specifically with smaller pyrimidines.
Pyrimidine
Plays a structural role in the nucleic acid sequence.
The consistent pairing of pyrimidines with purines maintains the DNA double helix's stability.
Purine
Purine is a heterocyclic aromatic organic compound that consists of two rings (pyrimidine and imidazole) fused together. It is water-soluble.
Pyrimidine
Smaller due to the single-ring structure.
The smaller size of pyrimidines complements the larger purines in base pairing.
Purine
A colourless crystalline compound with basic properties, forming uric acid on oxidation.
Pyrimidine
Pyrimidine is an aromatic heterocyclic organic compound similar to pyridine. One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has the nitrogen atoms at positions 1 and 3 in the ring.
Purine
A double-ringed, crystalline organic base, C5H4N4, that is the parent compound of a large group of biologically important compounds.
Pyrimidine
A single-ringed, crystalline organic base, C4H4N2, that is the parent compound of a large group of biologically important compounds.
Purine
Any of a group of substituted derivatives of purine, including the nitrogen bases adenine and guanine, which are components of nucleic acids. Uric acid, caffeine, theobromine, and theophylline are also purines.
Pyrimidine
Any of a group of substituted derivatives of pyrimidine, including the nitrogen bases uracil, cytosine, and thymine, which are components of nucleic acids. Barbiturates and certain other drugs are also pyrimidines.
Purine
(organic compound) Any of a class of organic heterocyclic compounds, composed of fused pyrimidine and imidazole rings, that constitute one of the two groups of organic nitrogenous bases (the other being the pyrimidines) and are components of nucleic acids.
Pyrimidine
(organic compound) A diazine in which the two nitrogen atoms are in the meta- positions; it is the basis of three of the bases found in DNA and RNA: thymine, uracil and cytosine
Purine
Any of several bases that are derivatives of purine
Pyrimidine
Any of several basic compounds derived from pyrimidine
Purine
A colorless crystalline nitrogen-containing organic base; the parent compound of various biologically important substances
Pyrimidine
A heterocyclic organic compound with a penetrating odor
Purine
Essential for energy transfer in cells (ATP).
ATP, an adenosine derivative, is a crucial energy carrier in cellular processes.
Common Curiosities
What is a pyrimidine?
A pyrimidine is a nitrogenous base with a single-ring structure found in nucleotides, including cytosine, thymine, and uracil.
Which bases are purines?
Adenine (A) and guanine (G) are purines.
What is the structure of purines?
Purines have a double-ring structure, one six-membered and one five-membered ring.
What is a purine?
A purine is a nitrogenous base with a double-ring structure found in nucleotides, including adenine and guanine.
How do purines pair in DNA?
In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).
What is the structure of pyrimidines?
Pyrimidines have a single six-membered ring.
Why are purines larger than pyrimidines?
Purines are larger due to their double-ring structure compared to the single-ring structure of pyrimidines.
What is the main function of pyrimidines?
Pyrimidines primarily serve as structural components in nucleic acids.
What is the significance of cAMP in cells?
cAMP (cyclic adenosine monophosphate) is a purine derivative important in various cell signaling pathways.
Which bases are pyrimidines?
Cytosine (C), thymine (T), and uracil (U) are pyrimidines.
How do pyrimidines pair in RNA?
In RNA, cytosine (C) pairs with guanine (G), and uracil (U) pairs with adenine (A).
What is ATP, and how is it related to purines?
ATP (adenosine triphosphate) is an energy carrier molecule that includes adenine, a purine.
How do the structures of purines and pyrimidines affect DNA stability?
The complementary pairing of purines and pyrimidines maintains the consistent width and stability of the DNA double helix.
What role do purines play besides in DNA/RNA?
Purines are involved in energy transfer (e.g., ATP) and cell signaling (e.g., cAMP).
Can purines and pyrimidines be found outside of nucleic acids?
Yes, purines and their derivatives (like ATP and cAMP) are involved in various cellular functions beyond nucleic acids. Pyrimidines are mostly structural in nucleic acids.
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Written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Co-written by
Maham Liaqat
