Question 1

Dihydrofolate reductase and thymidylate synthetase are major targets for anticancer drugs because

Accepted Answer

A)  these enzymes are unique in cancer cells. 
B)  cancer cell grow rapidly and are very dependent upon the activities of these enzymes. 
C)  they donate one-carbon groups. 
D)  cancer cells lack sufficient amounts of these enzymes. 
E)  All of the above 
A)  these enzymes are unique in cancer cells. 
B)  cancer cell grow rapidly and are very dependent upon the activities of these enzymes. 
C)  they donate one-carbon groups. 
D)  cancer cells lack sufficient amounts of these enzymes. 
E)  All of the above B

Question 2

Lesch-Nyhan syndrome, a result of hypoxanthine-guanine phosphoribosyltransferase deficiency, there is a/an .

Accepted Answer

A)  accumulation of hypoxanthine 
B)  accumulation of GMP 
C)  complete breakdown of purine biosynthesis 
D)  excess of degradation of IMP and GMP 
E)  accumulation of IMP 
A)  accumulation of hypoxanthine 
B)  accumulation of GMP 
C)  complete breakdown of purine biosynthesis 
D)  excess of degradation of IMP and GMP 
E)  accumulation of IMP D

Question 3

Which amino acid is not directly involved in the de novo biosynthesis of purines?

Accepted Answer

A)  glycine 
B)  glutamine 
C)  aspartate 
D)  arginine 
A)  glycine 
B)  glutamine 
C)  aspartate 
D)  arginine D

Question 4

Pyrimidines are catabolized to ammonia, bicarbonate, and either from cytosine or uracil) or from thymine).

Accepted Answer

A)  succinyl CoA; acetyl CoA 
B)  β-alanine; β-aminobutyrate 
C)  fumarate; succinyl CoA 
D)  acetyl CoA; succinyl CoA 
E)  acetyl CoA; acetyl CoA 
A)  succinyl CoA; acetyl CoA 
B)  β-alanine; β-aminobutyrate 
C)  fumarate; succinyl CoA 
D)  acetyl CoA; succinyl CoA 
E)  acetyl CoA; acetyl CoA

Question 5

Inhibition of ATCase by a nucleotide and activation of ATCase by a nucleotide keep the balance of purine and pyrimidine pools in E. coli.

Accepted Answer

A)  purine ATP); purine ATP) 
B)  pyrimidine; pyrimidine 
C)  pyrimidine; purine ATP) 
D)  purine ATP); pyrimidine 
A)  purine ATP); purine ATP) 
B)  pyrimidine; pyrimidine 
C)  pyrimidine; purine ATP) 
D)  purine ATP); pyrimidine

Question 6

The one-carbon group needed to convert dUMP into dTMP is derived from

Accepted Answer

A)  methanol. 
B)  5,10-methylenetetrahydrofolate. 
C)  glycine. 
D)  serine. 
E)  biotin. 
A)  methanol. 
B)  5,10-methylenetetrahydrofolate. 
C)  glycine. 
D)  serine. 
E)  biotin.

Question 7

The purine nucleotide cycle serves to form for the citric acid cycle while recycling formed in contracting muscle cells.

Accepted Answer

A)  ATP; AMP 
B)  fumarate; AMP 
C)  citrate; AMP 
D)  fumarate; ADP 
E)  ATP; fumarate 
A)  ATP; AMP 
B)  fumarate; AMP 
C)  citrate; AMP 
D)  fumarate; ADP 
E)  ATP; fumarate

Question 8

A ribose sugar is added to rings after their synthesis and to rings during their synthesis.

Accepted Answer

A)  purine; pyrimidine 
B)  pyrimidine; purine 
C)  purine; purine 
D)  pyrimidine; pyrimidine 
A)  purine; pyrimidine 
B)  pyrimidine; purine 
C)  purine; purine 
D)  pyrimidine; pyrimidine

Question 9

The excretory products of uric acid catabolism vary among organisms depending on their ability to .

Accepted Answer

A)  tolerate the end-product 
B)  remove the end-product to less toxic products 
C)  solubilize the end-product 
D)  remove an end-product like ammonia to the environment 
E)  All of the above 
A)  tolerate the end-product 
B)  remove the end-product to less toxic products 
C)  solubilize the end-product 
D)  remove an end-product like ammonia to the environment 
E)  All of the above

Question 10

In pyrimidine nucleotide biosynthesis orotate is the molecule that displaces the pyrophosphate group on PRPP.

Accepted Answer

A) True 
 B)False

Question 11

Which is the precursor of all pyrimidine ribo- and deoxyribonucleotides?

Accepted Answer

A)  dTMP 
B)  CTP 
C)  IMP 
D)  UMP 
A)  dTMP 
B)  CTP 
C)  IMP 
D)  UMP

Question 12

The cofactor, methylenetetrahydrofolate, can donate a variety of one-carbon groups as well as act as a reducing agent in biochemical reactions.

Accepted Answer

A) True 
 B)False

Question 13

Nucleotides have a β configuration about the anomeric carbon atom of the ribose or deoxyribose ring.

Accepted Answer

A) True 
 B)False

Question 14

The purine ring system is shown below. What is the source of the atoms 5 and 7 during de novo biosynthesis of purines?

Accepted Answer

A)  glycine 
B)  glutamine 
C)  aspartate 
D)  arginine 
A)  glycine 
B)  glutamine 
C)  aspartate 
D)  arginine

Question 15

Eukaryotic cells maintain the correct balance of deoxyribonucleotides needed in a species DNA by .

Accepted Answer

A)  controlling the activity of ribonucleotide reductase 
B)  controlling the specificity of ribonucleotide reductase 
C)  controlling both the specificity and activity of ribonucleotide reductase at the same time 
D)  feedback inhibition 
E)  controlling the balance of NADPH formed 
A)  controlling the activity of ribonucleotide reductase 
B)  controlling the specificity of ribonucleotide reductase 
C)  controlling both the specificity and activity of ribonucleotide reductase at the same time 
D)  feedback inhibition 
E)  controlling the balance of NADPH formed

Question 16

Which is the correct order for the synthesis of dTMP?

Accepted Answer

A)  dUDP → dUTP→ dTTP → dTDP→ dTMP 
B)  UMP → UDP→ dUDP → dUMP→ dTMP 
C)  UMP → TMP→ dTMP 
D)  UMP → dUMP→ dTMP 
A)  dUDP → dUTP→ dTTP → dTDP→ dTMP 
B)  UMP → UDP→ dUDP → dUMP→ dTMP 
C)  UMP → TMP→ dTMP 
D)  UMP → dUMP→ dTMP

Question 17

Which is not a direct precursor of pyrimidines in their de novo biosynthesis?

Accepted Answer

A)  HCO3-  
B)  glutamine 
C)  glycine 
D)  aspartate 
A)  HCO3-  
B)  glutamine 
C)  glycine 
D)  aspartate

Question 18

The purine ring system is shown below. What is the source of the C-6 atom during de novo biosynthesis of purines?

Accepted Answer

A)  carbon dioxide 
B)  tetrahydrofolate 
C)  carbamoyl phosphate 
D)  glycine 
A)  carbon dioxide 
B)  tetrahydrofolate 
C)  carbamoyl phosphate 
D)  glycine

Question 19

The pyrimidine ring system is shown below. What is the source of the carbons 4,5 and 6 during the de novo biosynthesis of pyrimidines?

Accepted Answer

A)  glutamine 
B)  aspartate 
C)  3 bicarbonate ions 
D)  pyruvate 
A)  glutamine 
B)  aspartate 
C)  3 bicarbonate ions 
D)  pyruvate

Question 20

When phosphoribosyl pyrophosphate PRPP) is used to form AMP from adenine as well as in numerous other cell reactions), the reaction is rendered irreversible because

Accepted Answer

A)  PRPP has such a high affinity for the enzyme involved. 
B)  the rate of the reaction favors formation of the products). 
C)  this reaction is thermodynamically feasible. 
D)  the presence of pyrophosphatase hydrolyzes pyrophosphate formed. 
E)  All of the above 
A)  PRPP has such a high affinity for the enzyme involved. 
B)  the rate of the reaction favors formation of the products). 
C)  this reaction is thermodynamically feasible. 
D)  the presence of pyrophosphatase hydrolyzes pyrophosphate formed. 
E)  All of the above

Exam 18: Nucleotide Metabolism

Dihydrofolate reductase and thymidylate synthetase are major targets for anticancer drugs because

Lesch-Nyhan syndrome, a result of hypoxanthine-guanine phosphoribosyltransferase deficiency, there is a/an .

Which amino acid is not directly involved in the de novo biosynthesis of purines?

Pyrimidines are catabolized to ammonia, bicarbonate, and either from cytosine or uracil) or from thymine).

Inhibition of ATCase by a nucleotide and activation of ATCase by a nucleotide keep the balance of purine and pyrimidine pools in E. coli.

The one-carbon group needed to convert dUMP into dTMP is derived from

The purine nucleotide cycle serves to form for the citric acid cycle while recycling formed in contracting muscle cells.

A ribose sugar is added to rings after their synthesis and to rings during their synthesis.

The excretory products of uric acid catabolism vary among organisms depending on their ability to .

In pyrimidine nucleotide biosynthesis orotate is the molecule that displaces the pyrophosphate group on PRPP.

Which is the precursor of all pyrimidine ribo- and deoxyribonucleotides?

The cofactor, methylenetetrahydrofolate, can donate a variety of one-carbon groups as well as act as a reducing agent in biochemical reactions.

Nucleotides have a β configuration about the anomeric carbon atom of the ribose or deoxyribose ring.

The purine ring system is shown below. What is the source of the atoms 5 and 7 during de novo biosynthesis of purines?

Eukaryotic cells maintain the correct balance of deoxyribonucleotides needed in a species DNA by .

Which is the correct order for the synthesis of dTMP?

Which is not a direct precursor of pyrimidines in their de novo biosynthesis?

The purine ring system is shown below. What is the source of the C-6 atom during de novo biosynthesis of purines?

The pyrimidine ring system is shown below. What is the source of the carbons 4,5 and 6 during the de novo biosynthesis of pyrimidines?

When phosphoribosyl pyrophosphate PRPP) is used to form AMP from adenine as well as in numerous other cell reactions), the reaction is rendered irreversible because

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Proteins: Three-Dimensional Structure and Function

Properties of Enzymes

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Glycolysis

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleic Acids

Dna Replication, Repair, and Recombination

Transcription and Rna Processing

Protein Synthesis

Recombinant Dna Technology

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