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Questions and Answers
What are the three main components of a nucleotide?
Which of the following correctly identifies the nitrogenous bases found in DNA and RNA?
Which sugar is found in RNA, and how does it differ from the sugar in DNA?
What role do nucleotides play as second messengers in hormonal action?
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What is the primary function of ATP and GTP in cellular processes?
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Allopurinol is used for the treatment of gout; which statement best describes its mechanism of action?
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Which of the following is NOT a function of nucleotides?
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Which synthetic analogue is specifically used in chemotherapy to inhibit DNA and RNA synthesis?
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What is formed when a nitrogenous base is added to a pentose sugar?
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Study Notes
Nucleic Acids
- Nucleic acids are long chains of repeating subunits called nucleotides.
- Nucleic acids are polymers.
- There are two main types of nucleic acids: DNA and RNA.
Nucleotide Structure
- A nucleotide consists of three components:
- Nitrogenous base
- Pentose sugar
- One or more phosphate groups.
Nucleosides
- A nucleoside is a molecule consisting of a nitrogenous base and a sugar.
- Addition of a base to the C1 of the pentose sugar produces a nucleoside via a glycosidic bond.
- There are two types of nucleosides:
- Ribonucleosides (contains ribose)
- Deoxyribonucleosides (contains deoxyribose)
Nitrogenous Bases
- There are two categories of nitrogenous bases:
- Purines:
- Adenine
- Guanine
- Both are found in DNA and RNA
- Pyrimidines:
- Cytosine (found in DNA and RNA)
- Thymine (found in DNA only)
- Uracil (found in RNA only)
- Purines:
Sugars
- There are two types of sugars found in nucleic acids:
- Deoxyribose (forms deoxyribonucleotides) found in DNA
- Ribose (forms ribonucleotides) found in RNA
Phosphate
- Phosphate is attached to the C5' of the pentose sugar.
- The phosphate group is attached via an ester bond.
Nucleotides
- A nucleotide is a nucleoside with one or more phosphate groups attached.
- A nucleotide consists of a nitrogenous base, a sugar, and a phosphate group.
Functions of Nucleotides
- Building blocks of DNA and RNA
- Source of energy - ATP and GTP
- Mediate the action of hormones - cAMP and cGMP are second messengers
- Coenzymes - NAD, FAD
- Activation of chemical compounds
- UDP-glucose - used in glycogen synthesis
- CDP-choline, CDP-ethanolamine - used in phospholipid synthesis
- Chemical group donors
- PAPS is a sulfate donor used in sulfolipid synthesis
- SAM is a methyl donor used in transmethylation reactions.
Synthetic Analogues
- Nucleotide analogues are prepared by altering the base ring or sugar part.
- Nucleotide analogues are used as drugs in clinical therapy.
Allopurinol
- Allopurinol is a purine analogue used to treat gout.
- It inhibits the xanthine oxidase enzyme, resulting in decreased uric acid synthesis.
Anti-Tumour Chemotherapy
- 5-fluorouracil (pyrimidine analogue) and 6-mercaptopurine (purine analogue) are used in anti-tumour chemotherapy.
- These compounds inhibit the growth of rapidly growing cancer cells by inhibiting the synthesis of DNA and RNA.
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Description
This quiz covers the fundamentals of nucleic acids, including DNA and RNA, as well as nucleotide structure and components. Test your knowledge on nitrogenous bases, nucleosides, and the different types of sugars involved in nucleic acid structures.
