Podcast
Questions and Answers
What is the main structural difference between DNA and RNA?
What is the main structural difference between DNA and RNA?
- DNA has a deoxyribose sugar, while RNA has a ribose sugar (correct)
- DNA is double-stranded, while RNA is single-stranded
- DNA has four bases (A, T, C, G), while RNA has five bases (A, U, C, G, T)
- DNA has a phosphate group, while RNA has a triphosphate group
Which of the following is a nucleoside analogue used in antiviral therapy?
Which of the following is a nucleoside analogue used in antiviral therapy?
- Adenine
- Acyclovir (correct)
- Guanine
- Ribose
What is the structural level of organization for a nucleotide?
What is the structural level of organization for a nucleotide?
- Secondary
- Tertiary
- Quaternary
- Primary (correct)
What is the importance of nucleoside and nucleotide analogues in medicine?
What is the importance of nucleoside and nucleotide analogues in medicine?
What is the difference between a nucleoside and a nucleotide?
What is the difference between a nucleoside and a nucleotide?
What is the orientation of the glycosidic bond in the syn conformation of a nucleotide?
What is the orientation of the glycosidic bond in the syn conformation of a nucleotide?
Which of the following is a physiologic mediator that is an adenosine nucleotide?
Which of the following is a physiologic mediator that is an adenosine nucleotide?
What is the structural component of coenzymes NAD and NADP that is derived from a nucleotide?
What is the structural component of coenzymes NAD and NADP that is derived from a nucleotide?
Which of the following is a structural component of the coenzyme S-adenosylmethionine (SAM), which is involved in methylation reactions?
Which of the following is a structural component of the coenzyme S-adenosylmethionine (SAM), which is involved in methylation reactions?
What is the orientation of the glycosidic bond in the anti conformation of a nucleotide?
What is the orientation of the glycosidic bond in the anti conformation of a nucleotide?
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Study Notes
Nucleosides
- Composed of a nitrogenous base and a pentose sugar.
- Linked by a glycosidic bond, specifically a β-glycosidic bond (upward directed at C1').
- Designation of bonds: “N” indicates attachment to the nitrogen atom of the base.
Types of Nucleosides
- Ribonucleosides: Contain ribose with a hydroxyl group at C2’.
- Purines: Form β-glycosidic bond between N9 (base) and C1’ (sugar). Nomenclature ends in -osine. Examples:
- Adenosine (A)
- Guanosine (G)
- Pyrimidines: Form β-glycosidic bond between N1 (base) and C1’ (sugar). Nomenclature ends in -idine. Examples:
- Cytidine (C)
- Uridine (U)
Functions of Nucleotides
- Serve as chemical energy carriers in cells.
- ATP: Known as the universal energy currency.
- GTP: Contains a purine base.
- CTP: Contains a pyrimidine base.
Nucleotides
- Adenosine monophosphate (AMP): Comprised of adenine, ribose, and one phosphate.
- Phosphate linkage: Found at C3’ and C5’ of sugar, leading to cyclic adenosine monophosphate (cAMP), which acts as a secondary messenger.
Deoxyribonucleotides
- Names and abbreviations:
- Deoxyadenosine monoPO4 (dAMP)
- Deoxyguanosine monoPO4 (dGMP)
- Deoxycytidine monoPO4 (dCMP)
- Deoxythymidine monoPO4 (dTMP)
- Inosine is formed when hypoxanthine attaches to a ribose ring, produced during purine nucleotide synthesis.
- Hypoxanthine: Not found in DNA, but a degradation product of purine bases.
Nucleobase Analogues
- Compounds that resemble natural nucleobases, important for clinical applications.
- Nomenclature based on phosphate attachment:
- "mono-" for one phosphate
- "di-" for two phosphates
- "tri-" for three phosphates
Purine Analogues
- Hypoxanthine: Contains one oxygen group at C6.
- Xanthine: Contains two oxygen groups at C2 and C6.
- Uric acid: Contains three oxygen groups at C2, C5, and C8.
Summary
- Nucleosides consist of a nitrogenous base and a sugar, with specific nomenclature depending on their structure.
- Nucleotides perform vital functions in energy transfer.
- Deoxyribonucleotides and nucleobase analogues have distinct characteristics essential for biological processes.
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