Question 1

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

Question 2

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
4)Allantoinase

Accepted Answer

A) 2; 3; 4; 1 
B) 1; 2; 4; 3 
C) 3; 4; 2; 1 
D) 1; 4; 2; 3 
A) 2; 3; 4; 1 
B) 1; 2; 4; 3 
C) 3; 4; 2; 1 
D) 1; 4; 2; 3

Question 3

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 4

What is the name of the compound below,which is an intermediate in the breakdown of some pyrimidines?

Accepted Answer

A)  N-carbamoyl-  -alanine 
B)  N-carbamoyl-  -aminoisobutyrate 
C)  dihydrothymine 
D)    -aminoisobutyrate 
A)  N-carbamoyl-  -alanine 
B)  N-carbamoyl-  -aminoisobutyrate 
C)  dihydrothymine 
D)    -aminoisobutyrate

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

Thymidylate synthase.This enzyme reactio

Question 6

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

Question 7

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

Accepted Answer

A)  ATP 
B)  cAMP 
C)  GTP 
D)  ribose 
A)  ATP 
B)  cAMP 
C)  GTP 
D)  ribose

Question 8

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)    -alanine 
C)  5-dihydrothymine 
D)  5-fluorouracil 
A)  primaquine 
B)    -alanine 
C)  5-dihydrothymine 
D)  5-fluorouracil

Question 9

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 10

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 11

Place the following steps in their proper order starting with dUMP and N5,N10-methylenetetrahydrofolate as substrates.
1)Formation of tetrahydrofolate
2)Formation of N5,N10-methylenetetrahydrofolate
3)Formation of 7,8-dihydrofolate

Accepted Answer

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

Question 12

Which nitrogen originates from aspartate?

Accepted Answer

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

Question 13

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

Accepted Answer

A)  0 
B)  2 
C)  4 
D)  8 
A)  0 
B)  2 
C)  4 
D)  8

Question 14

Describe how feedback inhibition by GDP may affect the flux of the ATP synthesis pathway.

Accepted Answer

GDP inhibits glutamine-PRPP am

Question 15

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

Question 16

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.

Accepted Answer

After exposure to glucagon,the

Question 17

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

Accepted Answer

A)  increased variety of nucleotides produced 
B)  increased half-life of mRNA 
C)  reduced energy expenditure 
D)  decreased regulation of nucleotide homeostasis 
A)  increased variety of nucleotides produced 
B)  increased half-life of mRNA 
C)  reduced energy expenditure 
D)  decreased regulation of nucleotide homeostasis

Question 18

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.

Accepted Answer

AMP could be converted to aden

Question 19

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 20

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

Accepted Answer

Nucleoside diphosphate kinase

Exam 18: Nucleotide Metabolism

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

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 4)Allantoinase

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

What is the name of the compound below,which is an intermediate in the breakdown of some pyrimidines?

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.

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

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

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?

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

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

Place the following steps in their proper order starting with dUMP and N5,N10-methylenetetrahydrofolate as substrates. 1)Formation of tetrahydrofolate 2)Formation of N5,N10-methylenetetrahydrofolate 3)Formation of 7,8-dihydrofolate

Which nitrogen originates from aspartate?

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

Describe how feedback inhibition by GDP may affect the flux of the ATP synthesis pathway.

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

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.

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

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.

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?

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

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

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

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 4)Allantoinase

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

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

Place the following steps in their proper order starting with dUMP and N⁵,N¹⁰-methylenetetrahydrofolate as substrates. 1)Formation of tetrahydrofolate 2)Formation of N⁵,N¹⁰-methylenetetrahydrofolate 3)Formation of 7,8-dihydrofolate