Exam 18: Nucleotide Metabolism

The enzymes required to convert PRPP to IMP in animal cells form a large protein complex called a(n) _. Describe the experimental evidence proving the existence of this complex.

The nitrogen atoms of a purine originate from all of the following amino acids EXCEPT

Relate the broad substrate specificity of nucleoside diphosphate kinase to its role in the consumption and synthesis of nucleoside triphosphates.

An E. coli strain that is unable to synthesize purines because of a mutation in the gene encoding the AIR synthetase is transfected with the human gene coding for hTrifGART. Would this strain would be able to undergo mitosis in purine-depleted media? Explain your answer.

Order the following steps involving the regeneration of ribonucleotide reductase that occurs in most animals so that it may carry out the formation of deoxyribonucleotides. (Note that not all steps are shown.) 1. Reduction of thioredoxin 2) Reduction of ribonucleotide reductase 3) Oxidation of thioredoxin reductase 4) Reduction of thioredoxin reductase

The conversion of ribose-1-phosphate to ATP via the salvage pathway would require the activity of several enzymes. Choose the answer that lists them in the order that they would act in this pathway.

Place the steps converting GMP to uric acid in the correct order. A. Conversion to guanine B. Conversion to guanosine C. Conversion to xanthine D. Conversion to uric acid

Which nitrogen originates from aspartate?

Which of the following is synthesized by a complex that requires an electrochemical gradient to function?

How would the flux of the pyrimidine biosynthetic pathway in E. coli cells be affected if the enzyme level of PRPP synthetase is upregulated? Explain your reasoning.

Which of the following is NOT a general role of nucleotides in cells?

Nonprimate mammals convert uric acid to allantoin. This reaction, catalyzed by urate oxidase, also generates which of the following products?

If HCO₃^- that is radioactively labeled with ¹³C is available, which carbon atom in the molecule below would ultimately be expected to be radioactive?

The carbon atoms of a purine originate from glycine and

CTP synthetase is inhibited by __________ and activated by _.

In analyzing the intermediates formed during the conversion of IMP to GMP and AMP, which molecule would one expect to find in the conversion to GMP but NOT in the conversion to AMP?

The biosynthesis of CTP is allosterically regulated at many steps. Which of the following is a major point of regulation?

To determine the role of glutaredoxin in the generation of deoxyribonucleotides by ribonucleotide reductase, which organisms would be the best to study?

If a mutation of the decarboxylase enzyme that functions in the biosynthetic pathway of UMP caused the pathway to halt at that step, which of the following would no longer occur?

Two biosynthesis steps are necessary to incorporate the carbon from HCO₃ ^- into carbamoyl aspartate. Describe the intermediate compound generated during this conversion.