Question 1

$\beta$-aminoisobutyrate is a breakdown product of

Accepted Answer

A)  dATP. 
B)  dUMP. 
C)  dCMP. 
D)  dTMP. 
A)  dATP. 
B)  dUMP. 
C)  dCMP. 
D)  dTMP.

Question 2

Uric acid is processed to allantoic acid, which is then secreted. In which of the following organisms does this occur?

Accepted Answer

A)  insects 
B)  bony fish 
C)  marine invertebrates 
D)  amphibians 
A)  insects 
B)  bony fish 
C)  marine invertebrates 
D)  amphibians

Question 3

An oncologist has a patient with dihydropyrimidine dehydrogenase deficiency. Which of the following is a chemotherapy agent that the doctor should be cautious about using with this patient because of serious side effects?

Accepted Answer

A)  "primaquine" 
B)  "$\beta$-alanine" 
C)  "5-dihydrothymine" 
D)  "5-fluorouracil" 
A)  "primaquine" 
B)  "$\beta$-alanine" 
C)  "5-dihydrothymine" 
D)  "5-fluorouracil"

Question 4

The biosynthesis of deoxynucleosides is important, yet different organisms require different sets of enzymes to carry it out. If 100 different species were analyzed, which enzyme is most likely to be found in all of them?

Accepted Answer

A)  ribonucleotide reductase 
B)  thioredoxin 
C)  glutaredoxin 
D)  glutathione reductase 
A)  ribonucleotide reductase 
B)  thioredoxin 
C)  glutaredoxin 
D)  glutathione reductase

Question 5

Identify the error in the diagram of the regulation of flux through the pyrimidine biosynthetic pathway shown below.

Accepted Answer

UMP does n

Question 6

Contrast the energy required to drive the synthesis of AMP from IMP with that required to drive the synthesis of GMP from IMP.

Accepted Answer

The synthesis of ATP requires

Question 7

If an alteration occurred in the activity site of the R1 subunit of E. coli ribonucleotide reductase that allowed dATP to bind but precluded ATP binding to the site, a possible result would be that ribonucleotide reductase

Accepted Answer

A)  would remain active under all conditions. 
B)  would be decreased when dATP bound both the activity and specificity sites. 
C)  activity would be increased when ATP bound the specificity site. 
D)  activity would be decreased when dCDP bound the catalytic site. 
A)  would remain active under all conditions. 
B)  would be decreased when dATP bound both the activity and specificity sites. 
C)  activity would be increased when ATP bound the specificity site. 
D)  activity would be decreased when dCDP bound the catalytic site.

Question 8

The chemotherapy agent 5-fluorouracil is usually degraded by which of the following enzymes, which requires administration of higher doses?

Accepted Answer

A)  "$\beta$-ureidopropionase" 
B)  "thymidine phosphorylase" 
C)  "dihydropyrimidine dehydrogenase" 
D)  "dihydropyrimidinase" 
A)  "$\beta$-ureidopropionase" 
B)  "thymidine phosphorylase" 
C)  "dihydropyrimidine dehydrogenase" 
D)  "dihydropyrimidinase"

Question 9

Explain how a general inhibitor of endonucleases would alter the homeostasis of mRNA and affect the nucleotide salvage pathway.

Accepted Answer

Endonucleases break down mRNA. If inhibi

Question 10

Contrast the source of the nitrogen required for the conversion of UTP to CTP in humans and bacteria.

Accepted Answer

Humans use glutamine

Question 11

A product of the first stage of purine biosynthesis is , whereas is a by-product of the second stage.

Accepted Answer

A)  fumarate; glycine 
B)  glutamine; glutamate 
C)  fumarate; glutamate 
D)  glutamate; fumarate 
A)  fumarate; glycine 
B)  glutamine; glutamate 
C)  fumarate; glutamate 
D)  glutamate; fumarate

Question 12

How many ATP are converted to ADP during the biosynthesis of CTP from UMP?

Accepted Answer

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

Question 13

Distinguish between the enzyme requirements for the regeneration of NADP+ needed during dNDP formation in humans and bacteria.

Accepted Answer

Humans use thioredoxin and thi

Question 14

The importance of stable free radicals in the mechanism of E. coli ribonucleotide reductase was identified in the early 1970s. The existence of stable radicals in a protein had not been previously observed. Which of the following amino acids can exist as a stable radical in ribonucleotide reductase?

Accepted Answer

A)  Cys 
B)  His 
C)  Ser 
D)  Glu 
A)  Cys 
B)  His 
C)  Ser 
D)  Glu

Question 15

Consider the breakdown of the four compounds below. Which would be expected to generate $\beta$-alanine?

Accepted Answer

A)  dATP 
B)  dGMP 
C)  dCMP 
D)  dTMP 
A)  dATP 
B)  dGMP 
C)  dCMP 
D)  dTMP

Question 16

Identify the carbon atom that is attacked by Cys439 in the first step of the E. coli ribonucleotide reductase mechanism.

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
A)  A 
B)  B 
C)  C 
D)  D

Question 17

The oxidation of dihydroorotate to orotate, which occurs during the biosynthesis of UMP, uses what molecule as an electron acceptor?

Accepted Answer

The answer of The oxidation of dihydroorotate to orotate, which...

Question 18

Which of the following organisms would generate this compound?

Accepted Answer

A)  nonprimate mammals 
B)  birds 
C)  cartilaginous fish 
D)  primates 
A)  nonprimate mammals 
B)  birds 
C)  cartilaginous fish 
D)  primates

Question 19

What would be the effect on thymidylate synthase activity if raltitrexed is present?

Accepted Answer

Thymidylat

Question 20

A nitrogen of a pyrimidine ring arises from which amino acid?

Accepted Answer

A)  aspartate 
B)  asparagine 
C)  glycine 
D)  alanine 
A)  aspartate 
B)  asparagine 
C)  glycine 
D)  alanine

Exam 18: Nucleotide Metabolism

β\betaβ -aminoisobutyrate is a breakdown product of

Uric acid is processed to allantoic acid, which is then secreted. In which of the following organisms does this occur?

An oncologist has a patient with dihydropyrimidine dehydrogenase deficiency. Which of the following is a chemotherapy agent that the doctor should be cautious about using with this patient because of serious side effects?

The biosynthesis of deoxynucleosides is important, yet different organisms require different sets of enzymes to carry it out. If 100 different species were analyzed, which enzyme is most likely to be found in all of them?

Identify the error in the diagram of the regulation of flux through the pyrimidine biosynthetic pathway shown below.

Contrast the energy required to drive the synthesis of AMP from IMP with that required to drive the synthesis of GMP from IMP.

If an alteration occurred in the activity site of the R1 subunit of E. coli ribonucleotide reductase that allowed dATP to bind but precluded ATP binding to the site, a possible result would be that ribonucleotide reductase

The chemotherapy agent 5-fluorouracil is usually degraded by which of the following enzymes, which requires administration of higher doses?

Explain how a general inhibitor of endonucleases would alter the homeostasis of mRNA and affect the nucleotide salvage pathway.

Contrast the source of the nitrogen required for the conversion of UTP to CTP in humans and bacteria.

A product of the first stage of purine biosynthesis is , whereas is a by-product of the second stage.

How many ATP are converted to ADP during the biosynthesis of CTP from UMP?

Distinguish between the enzyme requirements for the regeneration of NADP+ needed during dNDP formation in humans and bacteria.

Consider the breakdown of the four compounds below. Which would be expected to generate β\betaβ -alanine?

Identify the carbon atom that is attacked by Cys439 in the first step of the E. coli ribonucleotide reductase mechanism.

The oxidation of dihydroorotate to orotate, which occurs during the biosynthesis of UMP, uses what molecule as an electron acceptor?

Which of the following organisms would generate this compound?

What would be the effect on thymidylate synthase activity if raltitrexed is present?

A nitrogen of a pyrimidine ring arises from which amino acid?

Principles of Biochemistry

Physical Biochemistry: Energy Conversion, Water, and Membranes

Nucleic Acid Structure and Function

Protein Structure

Methods in Protein Biochemistry

Protein Function

Enzyme Mechanisms

Cell Signaling Systems

Glycolysis: a Paradigm of Metabolic Regulation

The Citrate Cycle

Oxidative Phosphorylation

Photosynthesis

Carbohydrate Structure and Function

Carbohydrate Metabolism

Lipid Structure and Function

Lipid Metabolism

Amino Acid Metabolism

Metabolic Integration

DNA Replication, Repair, and Recombination

RNA Synthesis, Processing, and Gene Silencing

Protein Synthesis, Posttranslational Modification, and Transport

Gene Regulation

Filters

$\beta$ -aminoisobutyrate is a breakdown product of

Distinguish between the enzyme requirements for the regeneration of NADP⁺needed during dNDP formation in humans and bacteria.

Consider the breakdown of the four compounds below. Which would be expected to generate $\beta$ -alanine?