Exam 19: Nucleotide Metabolism

Humans and great apes do not make the enzyme urate oxidase and are hence prone to gout from the crystallization of ________ in synovial fluid of joints.

The mechanism of action of dihydrofolate reductase inhibitors used for chemotherapy is based on their ability to block the synthesis of dTMP.

5-phosphoribosyl-α-D-1-pyrophosphate is a key intermediate in de novo synthesis of nucleotides but not in salvage pathways.

All six atoms in the pyrimidine ring are derived from two amino acids.

Glutamine amidotransferases require ATP hydrolysis to make the ________ of glutamine biosynthetically active.

While purines are assembled as nucleotides early in their biosynthetic pathway, the pyrimidine ring is assembled as a ________.

Which of the following enzymes is NOT primarily used in salvage of nucleic acids because the pyrophosphate product is rapidly hydrolyzed?

All of the dNTPs are produced in approximately the same amounts because the first step in each pathway is catalyzed by the same ribonucleotide reductase enzyme.

Which of the following compounds is NOT a precursor for nucleotide biosynthesis?

5-fluorouracil and 5-fluorodeoxyuridine are both prodrugs and potent inhibitors of DNA synthesis because they can be converted in the cell to 5-fluorodeoxyuridine monophosphate, an irreversible inhibitor of ________.

The initial end products of purine nucleotide biosynthesis are monophosphates.

The end product of purine catabolism in humans is:

Which of the following statements about purine biosynthesis in vertebrates is FALSE?

Inosine 5'-monophosphate, which contains the base hypoxanthine, is a common intermediate for ________ nucleotide biosynthesis.

Which statement about nucleotides is FALSE?

Ganciclovir or Acyclovir can be used treat herpes virus infections because they are nucleoside analogues that become phosphorylated by the viral thymidine kinase and interfere with viral ________.

Formyltransferases, which are ________ dependent, are involved in several steps of purine nucleotide biosynthesis.

Nucleoside phosphorylase cleaves a glycosidic bond to yield a base and either ribose-1-phosphate or deoxyribose-1-phosphate.