Nucleotides, the building blocks of nucleic acids like DNA and RNA, are made up of two different kinds of nitrogenous bases called pyrimidines and purines. These bases are essential for the storage and transmission of genetic information within living things.
Four carbon atoms and two nitrogen atoms make up the six-membered ring structure of the pyrimidine class of chemical molecules. One of the two main categories of nitrogenous bases that are present in nucleic acids—the other being purines—is these. The structure and operation of DNA and RNA, the genetic components of all living things, depend heavily on pyrimidines.
The following three pyrimidine bases are frequently found in nucleic acids:
- In DNA and RNA, cytosine, a pyrimidine base, forms hydrogen bonds with guanine, a purine base. It is a component of DNA and RNA, and its particular pairing with guanine aids in stabilizing DNA’s double-stranded structure.
- Another pyrimidine base that can be present in DNA is thymine (T). Through hydrogen bonding, it is paired with the purine base adenine. Thymine-adenine base pairing is a crucial component of the DNA double helix structure.
- In place of thymine, uracil (U) is a pyrimidine base found in RNA. Similar to the thymine-adenine pairing in DNA, it interacts with adenine in RNA.
Biological processes involving nucleic acids and energy metabolism are particularly dependent on the purines class of chemical substances. One of two varieties of nitrogenous bases—the other being pyrimidines—found in DNA and RNA. Additionally, purines play a role in energy transfer, cellular signaling, and many metabolic processes.
The following are the two main purines found in DNA and RNA:
- One of the four nitrogenous bases found in DNA, adenine (A) forms hydrogen bonds with thymine (T) to form the base pair. Adenine pairs with uracil (U) in RNA. Adenine is also a part of adenosine triphosphate (ATP), a key chemical for the storage and transfer of energy in cells.
- Another nitrogenous base included in both DNA and RNA is guanine (G). Guanine and cytosine (C), which couple up in RNA as well as DNA, form a hydrogen bond. Guanine is a crucial part of the compound guanosine triphosphate (GTP), which is used in many biological functions like protein synthesis and signal transduction.
47 differences between pyrimidines and purines:
|
S.No. |
Aspect |
Pyrimidines |
Purines |
|
1 |
Definition |
A type of nitrogenous base with a single-ring structure. |
A type of nitrogenous base with a double-ring structure. |
|
2 |
Chemical structure |
Consist of a six-membered ring made of carbon and nitrogen atoms. |
Consist of a fused five-membered and six-membered ring system. |
|
3 |
Molecular formula |
C4H4N2 |
C5H4N4 |
|
4 |
Number of rings |
Single-ring structure |
Double-ring structure |
|
5 |
Number of nitrogen atoms |
2 |
4 |
|
6 |
Types |
Cytosine, thymine, and uracil |
Adenine and guanine |
|
7 |
Presence in DNA and RNA |
Present in both DNA and RNA |
Present in both DNA and RNA |
|
8 |
Base pairs |
Cytosine pairs with guanine (C-G) in DNA and RNA |
Adenine pairs with thymine (A-T) in DNA |
|
9 |
Molecular weight |
Generally lighter |
Generally heavier |
|
10 |
Hydrogen bond donors |
Typically 2 hydrogen bond donors |
Typically 3 hydrogen bond donors |
|
11 |
Hydrogen bond acceptors |
Typically 2 hydrogen bond acceptors |
Typically 2 hydrogen bond acceptors |
|
12 |
Heteroatoms |
Contain carbon, nitrogen, and oxygen atoms. |
Contain carbon, nitrogen, and oxygen atoms. |
|
13 |
Chemical stability |
Generally more stable |
Relatively less stable |
|
14 |
Absorbance in UV spectroscopy |
Absorb at shorter wavelengths (around 260 nm) |
Absorb at longer wavelengths (around 270-280 nm) |
|
15 |
Role in genetic information |
Code for the genetic information in DNA and RNA. |
Code for the genetic information in DNA and RNA. |
|
16 |
Complementary base pairing |
Form complementary base pairs with other nucleotides. |
Form complementary base pairs with other nucleotides. |
|
17 |
Synthesis |
Synthesized through de novo biosynthesis pathways. |
Synthesized through de novo biosynthesis pathways. |
|
18 |
Degradation |
Broken down into smaller molecules through metabolic pathways. |
Broken down into smaller molecules through metabolic pathways. |
|
19 |
Nitrogenous base classification |
Classified as a pyrimidine base. |
Classified as a purine base. |
|
20 |
Common DNA modifications |
Can undergo DNA modifications like methylation. |
Can undergo DNA modifications like methylation. |
|
21 |
Presence of methyl groups |
May contain methyl groups (e.g., 5-methylcytosine). |
May contain methyl groups (e.g., N6-methyladenine). |
|
22 |
Uracil |
Found in RNA but not in DNA. |
Not present in DNA; replaced by thymine. |
|
23 |
RNA splicing |
Involved in RNA splicing processes. |
Not directly involved in RNA splicing. |
|
24 |
Role in RNA structure |
Can affect RNA structure and stability. |
Can affect RNA structure and stability. |
|
25 |
Tautomeric forms |
Exist in different tautomeric forms (keto and enol). |
Exist in different tautomeric forms (keto and enol). |
|
26 |
Role in energy metabolism |
Involved in energy metabolism pathways (e.g., citric acid cycle). |
Less directly involved in energy metabolism. |
|
27 |
Prevalence in nucleotides |
More common in nucleotides. |
Less common in nucleotides. |
|
28 |
Prevalence in nucleic acids |
More prevalent as the building blocks of nucleic acids. |
Less prevalent as the building blocks of nucleic acids. |
|
29 |
Role in genetic mutations |
Can lead to genetic mutations when altered. |
Can lead to genetic mutations when altered. |
|
30 |
Role in genetic diseases |
Mutations related to pyrimidines can cause genetic diseases (e.g., cystic fibrosis). |
Mutations related to purines can cause genetic diseases (e.g., Lesch-Nyhan syndrome). |
|
31 |
Role in RNA synthesis |
Involved in RNA synthesis and transcription. |
Involved in RNA synthesis and transcription. |
|
32 |
Role in DNA replication |
Involved in DNA replication and repair processes. |
Involved in DNA replication and repair processes. |
|
33 |
Role in cell signaling |
Can participate in cell signaling pathways. |
Can participate in cell signaling pathways. |
|
34 |
Structural differences |
Generally smaller and simpler in structure. |
Generally larger and more complex in structure. |
|
35 |
Biological importance |
Essential for the storage and transmission of genetic information. |
Essential for the storage and transmission of genetic information. |
|
36 |
Base stacking interactions |
Form weaker base stacking interactions. |
Form stronger base stacking interactions. |
|
37 |
Role in protein synthesis |
Involved in protein synthesis through translation. |
Involved in protein synthesis through translation. |
|
38 |
Role in cellular processes |
Participate in various cellular processes, including regulation and signaling. |
Participate in various cellular processes, including regulation and signaling. |
|
39 |
Presence in nucleosides |
Found in nucleosides like cytidine and uridine. |
Found in nucleosides like adenosine and guanosine. |
|
40 |
Presence in nucleotides |
Found in nucleotides like cytidine monophosphate (CMP) and uridine monophosphate (UMP). |
Found in nucleotides like adenosine monophosphate (AMP) and guanosine monophosphate (GMP). |
|
41 |
Role in secondary structure |
Can affect the secondary structure of nucleic acids. |
Can affect the secondary structure of nucleic acids. |
|
42 |
Role in DNA damage repair |
Involved in DNA damage repair processes. |
Involved in DNA damage repair processes. |
|
43 |
Nucleoside synthesis pathways |
Participate in de novo synthesis of nucleosides. |
Participate in de novo synthesis of nucleosides. |
|
44 |
Presence in anticancer drugs |
The basis for some anticancer drugs (e.g., 5-fluorouracil). |
Not typically used as the basis for anticancer drugs. |
|
45 |
Role in RNA modifications |
Can undergo RNA modifications (e.g., pseudouridine formation). |
Can undergo RNA modifications (e.g., m6A methylation). |
|
46 |
Presence in coenzymes |
Not typically found in coenzymes. |
Not typically found in coenzymes. |
|
47 |
Role in nucleotide synthesis |
Involved in the synthesis of nucleotides. |
Involved in the synthesis of nucleotides. |
Frequently Asked Questions (FAQs)
1. What distinguishes pyrimidines and purines from one another?
Purines (adenine and guanine) have a double-ring structure, whereas pyrimidines (cytosine, thymine, and uracil) have a single-ring structure. The two varieties of nitrogenous bases can be distinguished by their structural variations.
2. In DNA and RNA, how do pyrimidines and purines link up?
Adenine (A) and thymine (T) couple with one another in DNA through two hydrogen bonds, while cytosine (C) and guanine (G) pair with one another through three hydrogen bonds. Adenine (A) pairs similarly with uracil (U) in RNA.
3. What function does the metabolism of pyrimidines and purines serve?
The production of DNA and RNA, as well as other cellular functions like energy transfer (ATP and GTP), enzyme cofactors (NAD+ and FAD), and cell signaling (cyclic AMP), all depend on the metabolism of pyrimidines and purines. Various disorders can be caused by imbalances in the metabolism of pyrimidine and purine.
4. How do pyrimidines and purines break down and leave the body?
Pyrimidines and purines are broken down into simpler substances like uric acid, which is primarily eliminated through the urine. A buildup of too much uric acid can result in diseases like gout.
5. Are pyrimidines and purines used therapeutically in any way?
Yes, a number of drugs specifically target the pyrimidine and purine metabolic pathways. For instance, nucleotide synthesis is the focus of cancer treatments like 5-fluorouracil and methotrexate, and allopurinol is used to reduce uric acid levels in gout sufferers.
