Lecture 26

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What is the primary function of the salvage pathway in nucleotide metabolism?

To synthesize nucleotides from metabolic precursors
To catalyze the breakdown of nucleic acids
To recycle the free bases and nucleosides released from nucleic acid breakdown (correct)
To regulate the nucleotide pools in the cell

What is the common precursor for both purine and pyrimidine nucleotides?

PhosphoRibosylPyroPhosphate (PRPP) (correct)
Aspartate
Glycine
Ribose-5-phosphate

Which of the following is NOT a precursor for purine nucleotides?

CO2
Gln
Glycine
Aspartate (correct)

What is the purpose of continually synthesizing nucleotides in cells?

To regulate the rates of transcription and replication (B) Signup and view all the answers

Which of the following is a potential treatment for African trypanosomiasis?

Allopurinol (C) Signup and view all the answers

What is the origin of the N10 formyl group in purine nucleotides?

N10 Formyl THF (B) Signup and view all the answers

Which enzyme is responsible for salvaging free adenine in cells?

Adenosine PhosphoRibosylTransferase (A-PRT) (A) Signup and view all the answers

What is the result of a deficiency in Hypoxanthine-Guanine PhosphoRibosylTransferase (HG-PRT)?

Lesch-Nyhan syndrome (A) Signup and view all the answers

Which chemotherapeutic agent is a structural analog of tetrahydrofolate?

Methotrexate (B) Signup and view all the answers

What is the purpose of administering allopurinol to patients with Lesch-Nyhan syndrome?

To reduce uric acid production (A) Signup and view all the answers

What is the product of the reaction catalyzed by Adenosine PhosphoRibosylTransferase (A-PRT)?

AMP + PPi (A) Signup and view all the answers

Which of the following is NOT a symptom of Lesch-Nyhan syndrome?

Purine deficiency (B) Signup and view all the answers

What is the primary function of nucleotides in energy metabolism?

To carry chemical energy primarily through ATP and GTP (C) Signup and view all the answers

What is the significance of increased nucleotides biosynthesis in highly dividing cells?

It is a characteristic of cancer cells (C) Signup and view all the answers

What is the role of S-Adenosylmethionine in cellular metabolism?

It is involved in methyl group transfers (A) Signup and view all the answers

What is the primary source of nucleotides in de novo biosynthesis?

Amino acids, ribose-5-phosphate, CO2, and NH3 (B) Signup and view all the answers

What is the role of nucleotides in glycerolipid biosynthesis?

They are components of CDP-diacylglycerol (A) Signup and view all the answers

What is the significance of nucleotide analogs in anti-AIDS therapy?

They are used to inhibit the replication of HIV (B) Signup and view all the answers

What is the primary mechanism of regulation in de novo purine nucleotide synthesis?

Feedback inhibition (D) Signup and view all the answers

Which of the following is NOT a feedback inhibitor of PRPP synthesis?

AMP (B) Signup and view all the answers

What is the role of GTP in the synthesis of purine nucleotides?

Required for the synthesis of AMP (D) Signup and view all the answers

What is the effect of excess GMP on the formation of xanthylate (XMP)?

Inhibits the formation of XMP (C) Signup and view all the answers

What is the committed step of the de novo purine nucleotide synthesis pathway?

Glutamine-PRPP amidotransferase (A) Signup and view all the answers

What is the role of ATP in the synthesis of purine nucleotides?

Required for the synthesis of GMP (A) Signup and view all the answers

What is the effect of allopurinol on xanthine oxidase?

It is converted to oxypurinol, a strong competitive inhibitor (D) Signup and view all the answers

What is the end product of pyrimidine degradation in most organisms?

Urea (A) Signup and view all the answers

What is the fate of uric acid in different species?

It is species-specific (D) Signup and view all the answers

What is the result of the degradation of thymine?

Succinyl-CoA (D) Signup and view all the answers

What is the result of the degradation of CMP and UMP?

b-alanine (D) Signup and view all the answers

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 (D) Signup and view all the answers