Question 1

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 2

In the de novo synthesis of the deoxyribonucleotides,the deoxy form of PRPP is used in place of the PRPP used in the synthesis of the ribonucleotides.

Accepted Answer

A) True 
 B)False

Question 3

________ is a precursor for the de novo synthesis of AMP and GMP.

Accepted Answer

A) OMP 
B) XMP 
C) Adenylosuccinate 
D) IMP 
A) OMP 
B) XMP 
C) Adenylosuccinate 
D) IMP

Question 4

DNA synthesis is often measured by using radioactive

Accepted Answer

A) biotin. 
B) thymine. 
C) thiamine. 
D) thymidine. 
E) All of the above. 
A) biotin. 
B) thymine. 
C) thiamine. 
D) thymidine. 
E) All of the above.

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

Which is the correct order for the enzymes needed to convert UMP to CTP?

Accepted Answer

A) Nucleoside diphosphate kinase;uridylate kinase;CTP synthetase. 
B) Uridylate kinase;nucleoside diphosphate kinase;CTP synthetase. 
C) Uridylate kinase;CTP synthetase;nucleoside diphosphate kinase. 
D) CTP synthetase;nucleoside diphosphate kinase;uridylate kinase. 
A) Nucleoside diphosphate kinase;uridylate kinase;CTP synthetase. 
B) Uridylate kinase;nucleoside diphosphate kinase;CTP synthetase. 
C) Uridylate kinase;CTP synthetase;nucleoside diphosphate kinase. 
D) CTP synthetase;nucleoside diphosphate kinase;uridylate kinase.

Question 7

Ribonucleotides are produced from oxidation of the deoxyribonucleotides at the 2' carbon atom.

Accepted Answer

A) True 
 B)False

Question 8

Which occurs when CTP synthase converts UTP to CTP?

Accepted Answer

A) Glutamine → Glutamate 
B) Glutamate → Glutamine 
C) Aspartate → Glutamate 
D) Glutamine → Glycerate 
A) Glutamine → Glutamate 
B) Glutamate → Glutamine 
C) Aspartate → Glutamate 
D) Glutamine → Glycerate

Question 9

Which is a method by which the synthesis of AMP or GMP is regulated?

Accepted Answer

A) Covalent modification. 
B) Feedback inhibition. 
C) Feed-forward activation. 
D) Competitive inhibition. 
A) Covalent modification. 
B) Feedback inhibition. 
C) Feed-forward activation. 
D) Competitive inhibition.

Question 10

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

Accepted Answer

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

Question 11

Which is a common precursor in the de novo synthesis of purine nucleotides?

Accepted Answer

A) Inosine 5'-monophosphate. 
B) Xanthosine monophosphate. 
C) Orotate. 
D) Adenylosuccinate. 
A) Inosine 5'-monophosphate. 
B) Xanthosine monophosphate. 
C) Orotate. 
D) Adenylosuccinate.

Question 12

When a purine or a purine triphosphate is bound to the specificity site of ribonucleotide reductase,the activity of the catalytic site of the enzyme is specific for a pyrimidine or a pyrimidine triphosphate.

Accepted Answer

A) True 
 B)False

Question 13

Increased concentrations of ATP and GTP increase the rates of ________ nucleotide synthesis to help balance supplies of nucleotides in cells.

Accepted Answer

A) pyrimidine 
B) both purine and pyrimidine 
C) cytosine 
D) purine 
A) pyrimidine 
B) both purine and pyrimidine 
C) cytosine 
D) purine

Question 14

Which type of enzymes catalyze the phosphorylation of dADP,dGDP and dCDP?

Accepted Answer

A) Nucleotide phosphorylases. 
B) Nucleoside diphosphate kinases. 
C) Triphosphatases. 
D) Deoxyribosylphosphatases. 
A) Nucleotide phosphorylases. 
B) Nucleoside diphosphate kinases. 
C) Triphosphatases. 
D) Deoxyribosylphosphatases.

Question 15

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 16

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 product(s). 
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 product(s). 
C) this reaction is thermodynamically feasible. 
D) the presence of pyrophosphatase hydrolyzes pyrophosphate formed. 
E) All of the above.

Question 17

The ribonucleotides that are reduced to deoxyribonucleotides in most organisms are ________.

Accepted Answer

A) nucleosides 
B) mononucleotides 
C) dinucleotides 
D) trinucleotides 
A) nucleosides 
B) mononucleotides 
C) dinucleotides 
D) trinucleotides

Question 18

In the reactions catalyzed by xanthine oxidase,electrons are transferred to ________ to form ________.

Accepted Answer

A) O2;H2O2 
B) H₂O2;O2 
C) H₂O;O2 
D) O2;H₂O 
A) O2;H2O2 
B) H₂O2;O2 
C) H₂O;O2 
D) O2;H₂O

Question 19

The structure of carbamoyl phosphate synthetase of E.coli contains a tunnel that protects unstable intermediates from degradation by water.

Accepted Answer

A) True 
 B)False

Question 20

What is unusual about the reaction catalyzed by ribonucleotide reductase?

Accepted Answer

A) It involves the conversion of -SH groups to -OH groups. 
B) It uses a rare derivative of tetrahydrofolate. 
C) It has a free radical mechanism. 
D) This enzyme and its reaction occur only in a few species of archaebacteria. 
A) It involves the conversion of -SH groups to -OH groups. 
B) It uses a rare derivative of tetrahydrofolate. 
C) It has a free radical mechanism. 
D) This enzyme and its reaction occur only in a few species of archaebacteria.

Exam 18: Nucleotide Metabolism

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

In the de novo synthesis of the deoxyribonucleotides,the deoxy form of PRPP is used in place of the PRPP used in the synthesis of the ribonucleotides.

________ is a precursor for the de novo synthesis of AMP and GMP.

DNA synthesis is often measured by using radioactive

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

Which is the correct order for the enzymes needed to convert UMP to CTP?

Ribonucleotides are produced from oxidation of the deoxyribonucleotides at the 2' carbon atom.

Which occurs when CTP synthase converts UTP to CTP?

Which is a method by which the synthesis of AMP or GMP is regulated?

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

Which is a common precursor in the de novo synthesis of purine nucleotides?

When a purine or a purine triphosphate is bound to the specificity site of ribonucleotide reductase,the activity of the catalytic site of the enzyme is specific for a pyrimidine or a pyrimidine triphosphate.

Increased concentrations of ATP and GTP increase the rates of ________ nucleotide synthesis to help balance supplies of nucleotides in cells.

Which type of enzymes catalyze the phosphorylation of dADP,dGDP and dCDP?

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

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

The ribonucleotides that are reduced to deoxyribonucleotides in most organisms are ________.

In the reactions catalyzed by xanthine oxidase,electrons are transferred to ________ to form ________.

The structure of carbamoyl phosphate synthetase of E.coli contains a tunnel that protects unstable intermediates from degradation by water.

What is unusual about the reaction catalyzed by ribonucleotide reductase?

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 Atp Synthesis

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleic Acids

DNA Replication, repair, and Recombination

Transcription and RNA Processing

Protein Synthesis

Filters

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.

In the reactions catalyzed by xanthine oxidase,electrons are transferred to to form .