Exam 18: Nucleotide Metabolism

How many PRPP are required to synthesize two UMP and two CTP from carbamoyl aspartate?

What is the name of the compound below, which is part of the pathway that regenerates N⁵,N^{1 0}-methylenetetrahydrofolate?

Marine invertebrates express enzymes that allow for the conversion of uric acid to NH₄⁺. What is the correct order of the action of enzymes in this pathway? 1. Urate oxidase 2) Allantoicase 3) Urease

A part of the pathway of UMP biosynthesis is shown below. What intermediate is missing? What is the enzyme that generates this compound in the pathway? What is the enzyme that uses this compound as a substrate in the pathway? Carbamoyl phosphate + Aspartate $\rightarrow$ Carbamoyl aspartate $\rightarrow$ __________ $\rightarrow$ Orotate

Several cysteines play important roles in the mechanism of E. coli ribonucleotide reductase. Which is NOT a role carried out by cysteine in this enzyme?

Purine biosynthesis takes place in two stages. The first stage begins with ribose-5-phosphate and ends with

Which enzyme activity would be directly inhibited by the addition of methotrexate?

The possibility of ADA-SCID is indicated by than normal activity of .

Which of the following is a benefit of nucleotide salvage pathways compared with de novo synthesis?

A person is carrying out in vitro synthesis of uric acid from GMP. He or she wants to include all substrates and enzymes necessary. All EXCEPT should be included in the reaction mixture.

Propose a pathway by which AMP could be converted to hypoxanthine in a cell if there is a mutation that inactivated the enzyme AMP deaminase.

A person wishes to determine the role of PRPP synthetase in a newly discovered organism. He or she decides that a good way to do this would be to see what happens when PRPP synthetase is inhibited. Which of the following could be added to a cell from this organism to inhibit PRPP synthetase?

Describe how the levels of cAMP would change in a liver cell before and after exposure to glucagon. Compare these with the levels expected if the cell were previously exposed to an inhibitor of adenylate cyclase.

The conversion of adenosine to inosine is catalyzed by , which is deficient in .

Explain how the feedback inhibition of IMP dehydrogenase by GMP can increase the flux of the ATP synthesis pathway.

Aspartate contains four carbons. If all are radioactively labeled, how many carbons of UMP will be radioactively labeled?

The molecule below is a precursor to the formation of which of the following second messengers?

Consider a cell that is provided aspartate in which all carbons are radioactively labeled. Compounds in the cell are analyzed after the biosynthesis and subsequent breakdown of pyrimidines. Which of the following compounds would display no radioactivity signal during the analysis?

A mutation in the gene encoding which of the following enzymes would affect the synthesis of both AMP and GMP?

In severe combined immunodeficiency disease (SCID), ribonucleotide reductase activity is __________ because of an overabundance of _.