30 Questions
What is the primary function of the salvage pathway in nucleotide metabolism?
To recycle the free bases and nucleosides released from nucleic acid breakdown
What is the common precursor for both purine and pyrimidine nucleotides?
PhosphoRibosylPyroPhosphate (PRPP)
Which of the following is NOT a precursor for purine nucleotides?
Aspartate
What is the purpose of continually synthesizing nucleotides in cells?
To regulate the rates of transcription and replication
Which of the following is a potential treatment for African trypanosomiasis?
Allopurinol
What is the origin of the N10 formyl group in purine nucleotides?
N10 Formyl THF
Which enzyme is responsible for salvaging free adenine in cells?
Adenosine PhosphoRibosylTransferase (A-PRT)
What is the result of a deficiency in Hypoxanthine-Guanine PhosphoRibosylTransferase (HG-PRT)?
Lesch-Nyhan syndrome
Which chemotherapeutic agent is a structural analog of tetrahydrofolate?
Methotrexate
What is the purpose of administering allopurinol to patients with Lesch-Nyhan syndrome?
To reduce uric acid production
What is the product of the reaction catalyzed by Adenosine PhosphoRibosylTransferase (A-PRT)?
AMP + PPi
Which of the following is NOT a symptom of Lesch-Nyhan syndrome?
Purine deficiency
What is the primary function of nucleotides in energy metabolism?
To carry chemical energy primarily through ATP and GTP
What is the significance of increased nucleotides biosynthesis in highly dividing cells?
It is a characteristic of cancer cells
What is the role of S-Adenosylmethionine in cellular metabolism?
It is involved in methyl group transfers
What is the primary source of nucleotides in de novo biosynthesis?
Amino acids, ribose-5-phosphate, CO2, and NH3
What is the role of nucleotides in glycerolipid biosynthesis?
They are components of CDP-diacylglycerol
What is the significance of nucleotide analogs in anti-AIDS therapy?
They are used to inhibit the replication of HIV
What is the primary mechanism of regulation in de novo purine nucleotide synthesis?
Feedback inhibition
Which of the following is NOT a feedback inhibitor of PRPP synthesis?
AMP
What is the role of GTP in the synthesis of purine nucleotides?
Required for the synthesis of AMP
What is the effect of excess GMP on the formation of xanthylate (XMP)?
Inhibits the formation of XMP
What is the committed step of the de novo purine nucleotide synthesis pathway?
Glutamine-PRPP amidotransferase
What is the role of ATP in the synthesis of purine nucleotides?
Required for the synthesis of GMP
What is the effect of allopurinol on xanthine oxidase?
It is converted to oxypurinol, a strong competitive inhibitor
What is the end product of pyrimidine degradation in most organisms?
Urea
What is the fate of uric acid in different species?
It is species-specific
What is the result of the degradation of thymine?
Succinyl-CoA
What is the result of the degradation of CMP and UMP?
b-alanine
What is the purpose of withholding food rich in nucleotides and nucleic acids in the treatment of gout?
To reduce the amount of uric acid produced
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