Biomolecules - Nucleosides in RNA and DNA

• Introduction to nucleosides
• Structure of nucleosides
• Nucleosides in RNA
• Nucleosides in DNA
• Formation of nucleosides
• Purine nucleosides
• Pyrimidine nucleosides
• Examples of nucleosides
• Functions of nucleosides
• Conclusion

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Introduction to nucleosides

• Nucleosides are organic compounds composed of a nitrogenous base and a sugar molecule.
• They are the building blocks of nucleotides, which are essential for the structure and function of DNA and RNA.
• Nucleosides play crucial roles in various biological processes.

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Structure of nucleosides

• Nucleosides consist of two main components: a nitrogenous base and a sugar molecule.
• The nitrogenous base can be a purine (e.g., adenine, guanine) or a pyrimidine (e.g., cytosine, uracil, thymine).
• The sugar molecule is usually either ribose (in RNA) or deoxyribose (in DNA).

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Nucleosides in RNA

• In RNA, the four nucleosides are adenosine (A), guanosine (G), cytidine (C), and uridine (U).
• Adenosine pairs with uridine through two hydrogen bonds.
• Guanosine pairs with cytidine through three hydrogen bonds.
• Nucleosides in RNA are important for the synthesis and stability of RNA molecules.

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Nucleosides in DNA

• In DNA, the four nucleosides are deoxyadenosine (dA), deoxyguanosine (dG), deoxycytidine (dC), and thymidine (dT).
• Deoxyadenosine pairs with thymidine through two hydrogen bonds.
• Deoxyguanosine pairs with deoxycytidine through three hydrogen bonds.
• Nucleosides in DNA are crucial for the replication and storage of genetic information.

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Formation of nucleosides

• Nucleosides are formed by the attachment of a nitrogenous base to the sugar molecule.
• N-glycosidic bond formation between the base and the sugar molecule leads to the formation of nucleosides.
• The specific type of base and sugar determines the type of nucleoside.

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Purine nucleosides

• Purine nucleosides include adenosine and guanosine.
• Adenosine is composed of the base adenine and the sugar ribose.
• Guanosine is composed of the base guanine and the sugar ribose.
• They are crucial components of DNA, RNA, and various cellular processes.

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Pyrimidine nucleosides

• Pyrimidine nucleosides include cytidine, uridine, and thymidine.
• Cytidine is composed of the base cytosine and the sugar ribose.
• Uridine is composed of the base uracil and the sugar ribose.
• Thymidine is composed of the base thymine and the sugar deoxyribose.
• They play important roles in DNA and RNA synthesis.

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Examples of nucleosides

• Examples of nucleosides include adenosine, guanosine, cytidine, uridine, and thymidine.
• Adenosine is found in ATP (adenosine triphosphate) and is crucial for energy transfer in cells.
• Thymidine is present in DNA and is responsible for the storage of genetic information.
• These examples illustrate the importance of nucleosides in biological processes.

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Functions of nucleosides

• Nucleosides have diverse functions in cellular processes.
• They participate in energy metabolism, gene expression, and cell signaling.
• Nucleosides are involved in DNA and RNA synthesis, repair, and replication.
• They also play a role in immune responses and regulation of various biological pathways.

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Conclusion

• Nucleosides are essential components of DNA and RNA molecules.
• They are composed of a nitrogenous base and a sugar molecule.
• Nucleosides play crucial roles in cellular processes and are involved in various biological functions.
• Understanding nucleosides is fundamental to comprehend DNA and RNA structure and function.

11. Examples of nucleosides in RNA:

• Adenosine: A nucleoside composed of the base adenine and the sugar ribose.
• Guanosine: A nucleoside composed of the base guanine and the sugar ribose.
• Cytidine: A nucleoside composed of the base cytosine and the sugar ribose.
• Uridine: A nucleoside composed of the base uracil and the sugar ribose.

12. Examples of nucleosides in DNA:

• Deoxyadenosine (dA): A nucleoside composed of the base adenine and the sugar deoxyribose.
• Deoxyguanosine (dG): A nucleoside composed of the base guanine and the sugar deoxyribose.
• Deoxycytidine (dC): A nucleoside composed of the base cytosine and the sugar deoxyribose.
• Thymidine (dT): A nucleoside composed of the base thymine and the sugar deoxyribose.

13. ATP: Adenosine Triphosphate

• ATP is a nucleoside triphosphate composed of adenosine and three phosphate groups.
• It functions as a universal energy currency in cells, providing energy for various cellular processes.

14. Nucleoside and nucleotide difference:

• Nucleosides are composed of a nitrogenous base and a sugar molecule.
• Nucleotides are composed of a nucleoside and one or more phosphate groups.
• The presence of phosphate groups in nucleotides provides them with additional functions, such as energy storage and signal transduction.

15. Synthesis of nucleosides:

• Nucleosides can be synthesized in the body through enzymatic reactions.
• They can also be synthesized in the laboratory using chemical reactions.
• N-glycosidic bond formation between the base and the sugar is a key step in nucleoside synthesis.

16. Importance of nucleosides in DNA and RNA:

• Nucleosides are the building blocks of DNA and RNA molecules.
• They form the backbone of the nucleic acid chains.
• Nucleosides contribute to the stability, structure, and function of DNA and RNA.

17. Base pairing in nucleic acids:

• Nucleosides in DNA and RNA form complementary base pairs.
• Adenosine pairs with thymidine (DNA) or uridine (RNA) through hydrogen bonding.
• Guanosine pairs with cytidine through hydrogen bonding.

18. Hydrogen bonding in nucleosides:

• Hydrogen bonds play a crucial role in maintaining the stability and structure of nucleosides.
• Adenosine forms two hydrogen bonds with thymidine or uridine.
• Guanosine forms three hydrogen bonds with cytidine.

19. Structure comparison between ribose and deoxyribose:

• Ribose and deoxyribose are sugars present in nucleosides and nucleotides.
• Ribose has an additional hydroxyl group (-OH) at the 2’ carbon compared to deoxyribose.
• The presence or absence of this hydroxyl group affects the structure and properties of nucleosides and nucleotides.

20. Importance of nucleosides in cell signaling:

• Nucleosides, such as adenosine, have important roles in cell signaling.
• Adenosine acts as a signaling molecule and regulates various physiological processes.
• Abnormal levels of nucleosides can lead to diseases and disorders, highlighting their significance in cell signaling pathways.

21. Role of nucleosides in energy metabolism:

• Nucleosides, such as adenosine, play a crucial role in energy metabolism.
• Adenosine triphosphate (ATP) is the primary energy currency in cells.
• ATP is formed by the addition of three phosphate groups to adenosine diphosphate (ADP).
• During cellular respiration, ATP releases energy by breaking one of its phosphate bonds, forming adenosine diphosphate (ADP) and inorganic phosphate (Pi).
• This energy release is used for various cellular processes, including muscle contraction, active transport, and biosynthesis.

22. Nucleosides as building blocks of DNA and RNA:

• Nucleosides are the building blocks of DNA and RNA.
• They form the backbone of the nucleic acid chains.
• Nucleosides are connected by phosphodiester bonds between the sugar molecules and the phosphate groups.
• The sequence of nucleosides determines the genetic information stored in DNA and RNA.

23. Nucleosides as regulators of gene expression:

• Nucleosides can regulate gene expression by modulating cellular signaling pathways.
• Methylation of the cytosine base in DNA nucleosides can affect gene expression patterns.
• Modifications of RNA nucleosides, such as pseudouridine or N6-methyladenosine, can influence RNA stability and translation efficiency.

24. Importance of nucleosides in DNA replication:

• Nucleosides are essential for DNA replication, during which the double-stranded DNA is duplicated.
• Each nucleoside is added to the growing DNA strand by complementary base pairing with the template strand.
• The addition of nucleosides occurs in the 5’ to 3’ direction, following the DNA polymerase enzyme’s activity.

25. Impact of nucleoside analogs on viral replication:

• Nucleoside analogs are structurally similar to natural nucleosides but have slight modifications.
• These analogs can be incorporated into viral DNA or RNA during replication, disrupting the replication process.
• Nucleoside analogs are commonly used as antiviral drugs, such as acyclovir for herpes infections and AZT for HIV/AIDS.

26. Nucleoside analogs in cancer treatment:

• Nucleoside analogs can also be used in cancer treatment.
• They interfere with the replication and repair processes within cancer cells, leading to cell death.
• Examples of nucleoside analogs used in cancer chemotherapy include gemcitabine, cytarabine, and 5-fluorouracil.

27. Nucleoside reverse transcriptase inhibitors (NRTIs):

• NRTIs are a class of antiretroviral drugs used to treat HIV infection.
• They inhibit the reverse transcriptase enzyme, which converts viral RNA into DNA.
• NRTIs resemble natural nucleosides and incorporate into the viral DNA chain, preventing further replication.

28. Implications of nucleoside metabolism disorders:

• Disorders in nucleoside metabolism can have severe consequences.
• Deficiency in certain enzymes involved in nucleoside metabolism can lead to immune deficiencies, neurological disorders, and developmental abnormalities.
• Examples include adenosine deaminase deficiency (resulting in severe combined immunodeficiency) and Lesch-Nyhan syndrome (affecting purine metabolism).

29. Research and applications of nucleosides:

• Nucleosides continue to be a topic of scientific research and development.
• Ongoing studies aim to understand their role in various physiological processes, such as DNA repair, epigenetics, and diseases.
• Nucleosides and nucleoside analogs also have potential applications in drug delivery, diagnostic imaging, and targeted therapies.

30. Summary:

• Nucleosides are essential components of DNA and RNA, playing crucial roles in storing and transmitting genetic information.
• They are composed of a nitrogenous base and a sugar molecule, forming the backbone of nucleic acids.
• Nucleosides are involved in energy metabolism, gene expression, and cellular processes.
• Disorders in nucleoside metabolism can lead to severe health conditions.
• Ongoing research on nucleosides continues to deepen our understanding and expand their applications in various fields.