Question 1

Lesch-Nyhan syndrome,a result of hypoxanthine-guanine phosphoribosyltransferase deficiency,there is a(n) ________.

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 IMPF) C) and D)
G) None of the above D

Question 2

The purine ring system is shown below.What is the source of the N-1 atom during de novo biosynthesis of purines?

Accepted Answer

A)  Glycine.
B)  Glutamine.
C)  Aspartate.
D)  Arginine.E) C) and D)
F) All of the above

Question 3

Which structure below is PRPP?

Accepted Answer

A)  I
B)  II
C)  III
D)  IVE) C) and D)
F) A) and B)

Question 4

Modified nucleotides are rare and have not been shown to play significant roles in cell processes.

Accepted Answer

A) True 
 B)False  False

Question 5

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

Accepted Answer

A)  Glycine.
B)  Glutamine.
C)  Aspartate.
D)  Arginine.E) All of the above
F) A) and D)

Question 6

High levels of ________ will almost totally inhibit ATCase.

Accepted Answer

A)  CTP
B)  ATP
C)  CTP and UTP
D)  ADP and UDPE) A) and B)
F) A) and C)

Question 7

Enzymes that synthesize UMP are located on both sides of the mitochondrion in eukaryotic cells.

Accepted Answer

A) True 
 B)False

Question 8

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.E) B) and C)
F) None of the above

Question 9

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 10

Allantoin is the major end product of purine degradation in most mammals.

Accepted Answer

A) True 
 B)False

Question 11

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 formedF) A) and E)
G) A) and D)

Question 12

In eukaryotes all enzymes for the biosynthesis of the pyrimidine nucleotides occur exclusively in the cytosol.

Accepted Answer

A) True 
 B)False

Question 13

The source of the hydrogen to form water during the reduction of nucleoside triphosphates is ________.

Accepted Answer

A)  thioredoxin
B)  NADP
C)  NADH
D)  NADPH
E)   FADH₂F) A) and E)
G) All of the above

Question 14

The conversion of UTP to CTP involves ________.

Accepted Answer

A)  hydrolysis of a phosphate group
B)  oxidation of an OH group
C)  transfer of an NH₂ group
D)  formation of a carbon-carbon double bondE) A) and B)
F) A) and C)

Question 15

Four of the ten enzymes required for the biosynthesis of IMP are listed below.In which order do the reactions these enzymes catalyze occur during the synthesis of IMP? 
1.IMP cyclohydrolase
2.GAR synthase
3.glutamine-PRPP amidotransferase
4.AIR carboxylase

Accepted Answer

A)  1 → 2 → 3 → 4
B)  4 → 3 → 2 → 1
C)  3 → 2 → 4 → 1
D)  2 → 3 → 4 → 1E) A) and D)
F) B) and C)

Question 16

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.E) A) and D)
F) B) and C)

Question 17

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

Accepted Answer

A)  dTMP.
B)  CTP.
C)  IMP.
D)  UMP.E) C) and D)
F) A) and C) D

Question 18

Which is the source of the ribose ring in purine nucleotides?

Accepted Answer

A)  ATP.
B)  AMP.
C)  PRPP.
D)  cGDP.E) B) and D)
F) B) and C)

Question 19

Purines and pyrimidines formed during digestion of food are more likely to be salvaged than those formed inside the cell.

Accepted Answer

A) True 
 B)False

Question 20

The action of the enzyme urease on urea produces ________.Urease is found in ________.

Accepted Answer

A)  uracil;plants only
B)  uracil;all eukaryotes
C)  ammonia;all organisms
D)  ammonia;plants,crustaceans and some marine invertebratesE) B) and D)
F) A) and D)

Exam 18: Nucleotide Metabolism

Lesch-Nyhan syndrome,a result of hypoxanthine-guanine phosphoribosyltransferase deficiency,there is a(n) ________.

Correct AnswerverifiedD

The purine ring system is shown below.What is the source of the N-1 atom during de novo biosynthesis of purines?

Correct AnswerverifiedShow Answer

Which structure below is PRPP?

Correct AnswerverifiedShow Answer

Modified nucleotides are rare and have not been shown to play significant roles in cell processes.

Correct AnswerverifiedFalse

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

Correct AnswerverifiedShow Answer

High levels of ________ will almost totally inhibit ATCase.

Correct AnswerverifiedShow Answer

Enzymes that synthesize UMP are located on both sides of the mitochondrion in eukaryotic cells.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Allantoin is the major end product of purine degradation in most mammals.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

In eukaryotes all enzymes for the biosynthesis of the pyrimidine nucleotides occur exclusively in the cytosol.

Correct AnswerverifiedShow Answer

The source of the hydrogen to form water during the reduction of nucleoside triphosphates is ________.

Correct AnswerverifiedShow Answer

The conversion of UTP to CTP involves ________.

Correct AnswerverifiedShow Answer

Four of the ten enzymes required for the biosynthesis of IMP are listed below.In which order do the reactions these enzymes catalyze occur during the synthesis of IMP? 1.IMP cyclohydrolase 2.GAR synthase 3.glutamine-PRPP amidotransferase 4.AIR carboxylase

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedD

Which is the source of the ribose ring in purine nucleotides?

Correct AnswerverifiedShow Answer

Purines and pyrimidines formed during digestion of food are more likely to be salvaged than those formed inside the cell.

Correct AnswerverifiedShow Answer

The action of the enzyme urease on urea produces ________.Urease is found in ________.

Correct AnswerverifiedShow Answer

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D

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False

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D

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The action of the enzyme urease on urea produces .Urease is found in .

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