Question 1

Complete the following pathway of the degradation of UMP. UMP $\rightarrow$ Uridine $\rightarrow$ __________ $\rightarrow$ Dihydrouracil $\rightarrow$ NH4+ + HCO3- +
$\beta$-alanine

Accepted Answer

A)   uracil; N-carbamoyl- β\betaβ -aminoisobutyrate
B)   N-carbamoyl-uracil;  β\betaβ -alanine CoA
C)   uracil; N-carbamoyl- β\betaβ -alanine
D)   orotate; uracil  C

Question 2

In purines, __________ nitrogen atoms and __________ carbon atoms originate from glycine.

Accepted Answer

A)   0; 2
B)   1; 1
C)   2; 1
D)   1; 2 D

Question 3

Which enzyme activity would be directly reduced if fluorodeoxyuridine-5 ' -monophosphate is present?

Accepted Answer

A)   thymidine kinase
B)   thymidylate synthase
C)   dihydrofolate reductase
D)   serine hydroxymethyltransferase B

Question 4

Analysis of AMP and GMP synthesized in E. coli grown in medium containing 1 5N-labeled aspartate would show that

Accepted Answer

A)   AMP contained twice as much 1 5N than GMP.
B)   GMP contained twice as much 1 5N than AMP.
C)   AMP contained three times as much 1 5N than GMP.
D)   they contain the same levels of 1 5N.

Question 5

What is the name of the enzyme that catalyzes the methylation of dUMP to generate dTMP? Describe the mechanism of the enzyme and include the coenzyme requirement.

Accepted Answer

The answer of What is the name of the enzyme...

Question 6

What would be the effect on the enzyme activity of a mutant ribonucleotide reductases in which the metal-coordinated Tyr is missing? Explain your reasoning in the context of the role of the Tyr in the mechanism of the enzyme.

Accepted Answer

The answer of What would be the effect on the...

Question 7

Compare the regulatory effects of ATP and CTP on ATCase in E. coli.

Accepted Answer

The answer of Compare the regulatory effects of ATP and...

Question 8

Dihydropyrimidine dehydrogenase deficiencies can lead to an intolerance of high doses of 5-fluorouracil because 5-fluorouracil dihydropyrimidine dehydrogenase.

Accepted Answer

A)   is usually metabolized by
B)   inhibits
C)   allosterically activates
D)   denatures

Question 9

The conversion of hypoxanthine to IMP is catalyzed by , which is deficient in .

Accepted Answer

A)   HGPRT; Lesch-Nyhan syndrome
B)   adenosine deaminase; ADA-SCID
C)   xanthine oxidase; Lesch-Nyhan syndrome
D)   purine nucleoside phosphorylase; ADA-SCID

Question 10

A compound is added to a cell and dihydrofolate reductase activity is reduced. If this compound is , it can be predicted that a similar result would be seen if were added instead.

Accepted Answer

A)   methotrexate; aminopterin
B)   methotrexate; raltitrexed
C)   aminopterin; raltitrexed
D)   aminopterin; fluorodeoxyuridine-5 ' -monophosphate

Question 11

What enzymatic activity is NOT required during the biosynthesis of UMP from carbamoyl phosphate and aspartate?

Accepted Answer

A)   dehydrogenase
B)   decarboxylase
C)   phosphoribosyl transferase
D)   synthetase

Question 12

Contrast the binding of nucleotides to the activity site and specificity site on the R1 subunit of E. coli ribonucleotide reductase by choosing the nucleotide that can bind to the specificity site but NOT the activity site.

Accepted Answer

A)   ATP
B)   dTTP
C)   dATP
D)   dCDP

Question 13

Reduction in dTMP biosynthesis is NOT dependent upon _.

Accepted Answer

A)   methotrexate
B)   aminopterin
C)   raltitrexed
D)   dihydrofolate

Question 14

Dihydropyrimidine dehydrogenase deficiencies exist in approximately of humans and can result in complications when 5-fluorouracil is administered as a therapy.

Accepted Answer

A)   15%; cancer
B)   5%; cancer
C)   15%; autoimmunity
D)   5%; autoimmunity

Question 15

The transformation of ribose-5-phosphate to AIR in the first stage of purine biosynthesis in E. coli consumes the equivalent of 5 ATP. The second stage consumes

Accepted Answer

A)   an additional 5 ATP.
B)   more than 5 ATP.
C)   less than 5 ATP and generates 1 ATP.
D)   less than 5 ATP.

Question 16

Mutations in HGPRT cause Lesch-Nyhan syndrome. Mutations can lead to two different outcomes, both of which result in a reduction of guanine salvaging in cells. Contrast the two classes of mutations in HGPRT that can lead to the same result.

Accepted Answer

The answer of Mutations in HGPRT cause Lesch-Nyhan syndrome. Mutations...

Question 17

Which answer INCORRECTLY pairs a substrate and subsequent product of dihydropyrimidine dehydrogenase?

Accepted Answer

A)   thymine; dihydrothymine
B)   uracil; dihydrouracil
C)   adenine; dihydroadenine
D)   5-fluorouracil; fluorodihydrouracil

Question 18

Analysis of enzyme activities in a cell in the absence and presence of AMP and GMP is completed. Which enzyme would show lower activity when AMP is added but not when GMP is added?

Accepted Answer

A)   glutamine-PRPP aminotransferase
B)   adenylosuccinate synthase
C)   IMP dehydrogenase
D)   PRPP synthetase

Question 19

Glutamine-PRPP amidotransferase is a tetrameric enzyme that displays sigmoidal kinetics when no inhibitors are present. In the presence of either GTP or ATP the kinetics curve is sigmoidal. Why does this difference in kinetics occur?

Accepted Answer

The answer of Glutamine-PRPP amidotransferase is a tetrameric enzyme that...

Question 20

How many of the nitrogens in orotidine-5 ' -monophosphate arise from glutamine?

Accepted Answer

A)   0
B)   1
C)   2
D)   3

Exam 18: Nucleotide Metabolism

In purines, nitrogen atoms and carbon atoms originate from glycine.

Which enzyme activity would be directly reduced if fluorodeoxyuridine-5 ^' -monophosphate is present?

Analysis of AMP and GMP synthesized in E. coli grown in medium containing ^{1 5}N-labeled aspartate would show that

What is the name of the enzyme that catalyzes the methylation of dUMP to generate dTMP? Describe the mechanism of the enzyme and include the coenzyme requirement.

What would be the effect on the enzyme activity of a mutant ribonucleotide reductases in which the metal-coordinated Tyr is missing? Explain your reasoning in the context of the role of the Tyr in the mechanism of the enzyme.

Compare the regulatory effects of ATP and CTP on ATCase in E. coli.

Dihydropyrimidine dehydrogenase deficiencies can lead to an intolerance of high doses of 5-fluorouracil because 5-fluorouracil dihydropyrimidine dehydrogenase.

The conversion of hypoxanthine to IMP is catalyzed by , which is deficient in .

A compound is added to a cell and dihydrofolate reductase activity is reduced. If this compound is , it can be predicted that a similar result would be seen if were added instead.

What enzymatic activity is NOT required during the biosynthesis of UMP from carbamoyl phosphate and aspartate?

Contrast the binding of nucleotides to the activity site and specificity site on the R1 subunit of E. coli ribonucleotide reductase by choosing the nucleotide that can bind to the specificity site but NOT the activity site.

Reduction in dTMP biosynthesis is NOT dependent upon _.

Dihydropyrimidine dehydrogenase deficiencies exist in approximately of humans and can result in complications when 5-fluorouracil is administered as a therapy.

The transformation of ribose-5-phosphate to AIR in the first stage of purine biosynthesis in E. coli consumes the equivalent of 5 ATP. The second stage consumes

Mutations in HGPRT cause Lesch-Nyhan syndrome. Mutations can lead to two different outcomes, both of which result in a reduction of guanine salvaging in cells. Contrast the two classes of mutations in HGPRT that can lead to the same result.

Which answer INCORRECTLY pairs a substrate and subsequent product of dihydropyrimidine dehydrogenase?

Analysis of enzyme activities in a cell in the absence and presence of AMP and GMP is completed. Which enzyme would show lower activity when AMP is added but not when GMP is added?

Glutamine-PRPP amidotransferase is a tetrameric enzyme that displays sigmoidal kinetics when no inhibitors are present. In the presence of either GTP or ATP the kinetics curve is sigmoidal. Why does this difference in kinetics occur?

How many of the nitrogens in orotidine-5 ^' -monophosphate arise from glutamine?

Exam 18: Nucleotide Metabolism

Complete the following pathway of the degradation of UMP. UMP →\rightarrow→ Uridine →\rightarrow→ __________ →\rightarrow→ Dihydrouracil →\rightarrow→ NH4+ + HCO3- + β\betaβ -alanine

In purines, __________ nitrogen atoms and __________ carbon atoms originate from glycine.

Which enzyme activity would be directly reduced if fluorodeoxyuridine-5 ' -monophosphate is present?

Analysis of AMP and GMP synthesized in E. coli grown in medium containing 1 5N-labeled aspartate would show that

What is the name of the enzyme that catalyzes the methylation of dUMP to generate dTMP? Describe the mechanism of the enzyme and include the coenzyme requirement.

What would be the effect on the enzyme activity of a mutant ribonucleotide reductases in which the metal-coordinated Tyr is missing? Explain your reasoning in the context of the role of the Tyr in the mechanism of the enzyme.

Compare the regulatory effects of ATP and CTP on ATCase in E. coli.

Dihydropyrimidine dehydrogenase deficiencies can lead to an intolerance of high doses of 5-fluorouracil because 5-fluorouracil dihydropyrimidine dehydrogenase.

The conversion of hypoxanthine to IMP is catalyzed by , which is deficient in .

A compound is added to a cell and dihydrofolate reductase activity is reduced. If this compound is , it can be predicted that a similar result would be seen if were added instead.

What enzymatic activity is NOT required during the biosynthesis of UMP from carbamoyl phosphate and aspartate?

Contrast the binding of nucleotides to the activity site and specificity site on the R1 subunit of E. coli ribonucleotide reductase by choosing the nucleotide that can bind to the specificity site but NOT the activity site.

Reduction in dTMP biosynthesis is NOT dependent upon _.

Dihydropyrimidine dehydrogenase deficiencies exist in approximately of humans and can result in complications when 5-fluorouracil is administered as a therapy.

The transformation of ribose-5-phosphate to AIR in the first stage of purine biosynthesis in E. coli consumes the equivalent of 5 ATP. The second stage consumes

Mutations in HGPRT cause Lesch-Nyhan syndrome. Mutations can lead to two different outcomes, both of which result in a reduction of guanine salvaging in cells. Contrast the two classes of mutations in HGPRT that can lead to the same result.

Which answer INCORRECTLY pairs a substrate and subsequent product of dihydropyrimidine dehydrogenase?

Analysis of enzyme activities in a cell in the absence and presence of AMP and GMP is completed. Which enzyme would show lower activity when AMP is added but not when GMP is added?

Glutamine-PRPP amidotransferase is a tetrameric enzyme that displays sigmoidal kinetics when no inhibitors are present. In the presence of either GTP or ATP the kinetics curve is sigmoidal. Why does this difference in kinetics occur?

How many of the nitrogens in orotidine-5 ' -monophosphate arise from glutamine?

In purines, nitrogen atoms and carbon atoms originate from glycine.

Which enzyme activity would be directly reduced if fluorodeoxyuridine-5 ^' -monophosphate is present?

Analysis of AMP and GMP synthesized in E. coli grown in medium containing ^{1 5}N-labeled aspartate would show that

How many of the nitrogens in orotidine-5 ^' -monophosphate arise from glutamine?