Deck 23: Nucleotide Metabolism

Question 1

Matching
Choose the correct answer from the list.Not all the answers will be used.

The precursor to AMP and GMP is ______.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Answer 1

IMP

Question 2

The synthesis of the dNTPs required for DNA production must be controlled by ________ in order to ensure minimal ________ activity from excess of one dNTP over the other dNTPs.

A)feedback inhibition;mutagenic
B)feed forward activation;synthesis
C)substrate availability;mutagenesis
D)secondary messenger systems;synthesis
E)feed forward;mutagenic

Answer 2

feedback inhibition;mutagenic

Question 3

Matching
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During the turnover of nucleic acids some purines can be reincorporated into nucleotides via _____ pathways.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Answer 3

salvage

Question 4

Matching
Choose the correct answer from the list.Not all the answers will be used.

Mechanism-based inhibitors are also called _____ substrates.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Question 5

Matching
Choose the correct answer from the list.Not all the answers will be used.


-Deoxyribonucleotides are synthesized by ______ of the corresponding ribonucleotide's 2' carbon.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Question 6

John Buchanan began the elucidation of the synthesis of purine nucleotides by studying _______ excreted by pigeons fed isotopically labeled compounds.

A)"xanthine"
B)"hypoxanthine"
C)"uric acid"
D)" $\beta$ -alanine"
E)" $\beta$ -aminoisobutyrate"

Question 7

Which of the following organisms excrete uric acid?
(I)primates
(II)marine invertebrates
(III)insects
(IV)mammals other than primates

A)I,IV
B)I,III
C)IV only
D)I only
E)II,III

Question 8

Matching
Choose the correct answer from the list.Not all the answers will be used.

Gout is treated using the compound ______.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Question 9

Matching
Choose the correct answer from the list.Not all the answers will be used.

______ compounds are effective anticancer agents.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Question 10

The conversion of dUMP to dTMP by thymidylate synthase requires which of the following cofactors?
(I)thioredoxin
(II)N⁵,N¹⁰-methylenetetrahydrofolate
(III)S-adenosylmethionine

A)I and II
B)I only
C)II only
D)II and III
E)I and III

Question 11

Which of the choices correctly represents the synthesis of dTTP as represented by the following reactions?
(I)dUMP + N⁵,N¹⁰-methylenetetrahydrofolate $\to$ dTMP + dihydrofolate
(II)dTMP + ATP $\to$ dTTP + P_i
(III)dUTP + H₂O $\to$ dUMP + PP_i
(IV)dUTP + N⁵,N¹⁰-methylenetetrahydrofolate $\to$ dTTP + dihydrofolate

A)I $\to$ II $\to$ IV
B)IV only
C)III $\to$ IV $\to$ I $\to$ II
D)III $\to$ I $\to$ II
E)III $\to$ I

Question 12

Matching
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In purine synthesis the byproduct released when aspartate functions as an amino group donor is ________.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Question 13

Hydroxylation of IMP to form GMP occurs in conjunction with the ________ of _______.

A)oxidation;NADH
B)reduction;NAD⁺
C)oxidation;NADPH
D)reduction;NADP⁺
E)none of the above

Question 14

The symptoms of Lesch-Nyhan syndrome are caused by a deficiency of which of the following enzymes?

A)adenine phosphoribosyltransferase
B)HGPRT (hypoxanthine-guanine phosphoribosyltransferase)
C)adenosine deaminase
D)dihydrofolate reductase
E)xanthine oxidase

Question 15

Matching
Choose the correct answer from the list.Not all the answers will be used.

Class I ribonucleotide reductases (RNR)contain a(n)______ prosthetic group.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Question 16

The first step in pyrimidine biosynthesis is the formation of

A)carbamoyl phosphate.
B)carbamoyl aspartate.
C)β-aminoisobutyrate.
D)dihydroorotate.
E)none of the above

Question 17

Matching
Choose the correct answer from the list.Not all the answers will be used.

Purines are degraded to ______.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Question 18

Which of the following correctly describes the formation of CTP?

A)UTP + Glutamine + ATP + H₂O $\to$ Glutamate + ADP + P_i + CTP
B)UMP + ATP + H₂O + Glutamine $\to$ CMP + Glutamate + ADP + P_i
C)TTP + N⁵,N¹⁰-Methylenetetrahydrofolate $\to$ CTP + Dihydrofolate
D)UMP + Glutamine $\to$ Glutamate + CTP
E)CMP + Glutamine + ATP $\to$ CTP + Glutamate + ADP + P_i

Question 19

Myoadenylate deaminase deficiency is most evident in ______ tissue.

A)liver
B)connective
C)neural
D)muscle
E)brain

Question 20

Matching
Choose the correct answer from the list.Not all the answers will be used.

The electrons used to convert an NDP to a dNDP ultimately come from ______.

A) fumarate
B) NADPH
C) salvage
D) uric acid
E) oxidation
F) XMP
G) iron
H) allopurinol
I) IMP
J) Oxidation
K) therapeutic
L) suicide
M) molybdenum
N) FADH
O) Malonyl-CoA
P) reduction
Q) antifolate

Question 21

Which of the following is not required for purine biosynthesis?
(I)aspartate
(II)glycine
(III)glutamine
(IV)formyl addition to tetrahydrofolate

A)I only
B)II,IV
C)II,III
D)IV only
E)All of the above are required.

Question 22

Which of the following statements about nucleotide synthesis is (are)true?
(I)Most dietary nucleotides are salvaged and used in DNA synthesis.
(II)Most nucleotides in cells are from de novo pathways.
(III)Most nucleotides in cells are salvaged and used in RNA synthesis.

A)I,II
B)I only
C)II only
D)II,IV
E)III only

Question 23

Which of the following statements is TRUE?

A)PRPP is an effective feedback inhibitor of nucleotide synthesis.
B)GTP serves as the energy input for AMP synthesis from IMP.
C)Oxidation of ribosyl moieties to produce deoxynucleotides occurs at the diphosphate level.
D)Thymidylate synthase methylates dUTP to produce dTTP.
E)All of the above are true.

Question 24

The thymidylate synthase reaction is unique because

A)THF is regenerated by the same enzyme.
B)THF is regenerated via a two-step reaction.
C)THF is oxidized to DHF;no other reaction alters the THF oxidation state.
D)None of the above is correct.
E)All of the above are correct.

Question 25

Individuals that do not consume adequate folic acid have serious problems with the

A)synthesis of dATP.
B)synthesis of dCTP.
C)synthesis of dGTP.
D)synthesis of dTTP.
E)all of the above

Question 26

Which of the following reactions is NOT catalyzed by nucleoside diphosphate kinase?

A)GDP + ATP $\to$ GTP + ADP
B)UDP + ATP $\to$ UTP + ADP
C)CDP + ATP $\to$ CTP + ADP
D)dGDP + ATP $\to$ dGTP + ADP
E)It catalyzes all the above.

Question 27

What category of reaction converts orotate monophosphate (OMP)into uracil monophosphate (UMP)?

A)a transamination
B)a methylation
C)a decarboxylation
D)a carboxylation
E)none of the above

Question 28

Atoms from which of the following amino acids are utilized in pyrimidine biosynthesis?
(I)glutamine
(II)glycine
(III)asparagine
(IV)aspartate

A)I,II
B)I)III
C)I,IV
D)II,III
E)II,IV

Question 29

The proposed mechanism of the Class I RNR involves

A)electron transfer directly from substrate to tyrosine 122.
B)electron transfer from substrate to various cysteine residues.
C)an exposed tyrosine which accepts an electron from the ribosyl radical.
D)electron donation to external reducing agents.
E)none of the above

Question 30

The amino group added to the C6 position of IMP to form AMP is derived from

A)"aspartate."
B)"asparagine."
C)"glutamine."
D)" $\alpha$ -ketoglutarate."
E)"arginine."

Question 31

Which of the following pathways produces the sugar moiety used for nucleotide synthesis?

A)glycolysis
B)Calvin cycle
C)pentose phosphate
D)glycogen metabolism
E)none of the above

Question 32

Which best describes the synthesis of purine nucleotides?

A)The basic ring structure,orotate,is synthesized and then linked to PRPP.This is then modified to produce either GMP or AMP.
B)The basic ring structure,inosine,is synthesized and then linked to PRPP.This is then modified to produce either GMP or AMP.
C)The basic ring structure,orotate,is synthesized stepwise on PRPP.This is then modified to produce either GMP or AMP.
D)The basic ring structure,inosine,is synthesized stepwise on PRPP.This is then modified to produce either GMP or AMP.
E)The basic ring structure,orotate,is synthesized and then linked to PRPP.This is then modified to produce either UMP or CMP.

Question 33

The end products of pyrimidine catabolism are

A)"uric acid and glyoxylic acid."
B)"uric acid and allantoin."
C)" $\beta$ -alanineand $\beta$ -aminoisobutyrate."
D)" $\beta$ -alanine and $\alpha$ -ketoglutarate."
E)"none of the above"

Question 34

The disease gout is characterized by high levels of ____,which forms crystal deposits in joints and is treated by inhibition of _______.

A)uric acid;urate oxidase
B)uric acid;xanthine oxidase
C)urea;urate oxidase
D)xanthine;xanthine oxidase
E)none of the above

Question 35

The amino group added to the C2 position on IMP to form GMP is derived from

A)"aspartate"
B)"aspargine"
C)"glutamine"
D)" $\alpha$ -ketoglutarate"
E)"arginine"

Question 36

Which of the following sequences for uric acid catabolism is correct for marine invertebrates?

A)uric acid $\to$ allantoin $\to$ allantoic acid $\to$ urea $\to$ NH₄⁺
B)uric acid $\to$ allantoic acid $\to$ urea $\to$ NH₄⁺
C)uric acid $\to$ allantoin $\to$ urea $\to$ NH₄⁺
D)uric acid $\to$ allantoin $\to$ allantoic acid $\to$ urea
E)none of the above

Question 37

The synthesis of 5-phosphoribosylamine from PRPP is
(I)inhibited allosterically by ATP and GTP.
(II)activated by PRPP via feed forward activation.
(III)controlled by cAMP dependent phosphorylation.

A)I,II,III,
B)I,II
C)II,III
D)II only
E)III only

Question 38

The symptoms of severe combined immunodeficiency syndrome (SCID)are caused by a deficiency of which of the following enzymes?

A)adenine phosphoribosyltransferase
B)HGPRT (hypoxanthine-guanine phosphoribosyltransferase)
C)adenosine deaminase
D)dihydrofolate reductase
E)xanthine oxidase

Question 39

Orotate is synthesized from

A)glycine and carbamoyl phosphate.
B)arginine and carbamoyl phosphate.
C)aspartate and carbamoyl phosphate.
D)aspartate and glutamine.
E)asparagine and glutamine.

Question 40

Addition of pyrophosphate to which of the following occurs during the first step of purine biosynthesis?

A)5-phosphoribosyl phosphate
B)ribulose-5-phosphate
C)ribose-5-phosphate
D)ribose
E)phosphribosylamine

Question 41

A final common product from both purine degradation and pyrimidine degradation is

A)uric acid.
B)aspartate.
C)ribose-1-phosphate.
D)ribose-5-phosphate.
E)malonyl-CoA.

Question 42

Acyclovir is a derivative of which of the following?

A)a pyrimidine
B)a purine
C)malonic semialdehyde
D)dihydrofolate
E)thioredoxin

Question 43

The last step in purine degradation
(I)generates hydrogen peroxide as a byproduct.
(II)utilizes molecular oxygen.
(III)is inhibited by methotrexate.
(IV)requires NAD⁺.

A)I,II,III,IV
B)I,II,IV
C)II,IV
D)I,III,IV
E)I,II

Question 44

Recombinant forms of the enzyme urate oxidase are available for therapeutic purposes.Based on the information in this chapter,in which of the following conditions might this therapy be useful?

A)myoadenylate deaminase deficiency
B)severe combined immunodeficiency disease
C)gout
D)toxoplasmosis
E)folate deficiency

Question 45

Which of the following is correct regarding pyrimidine synthesis?

A)carbamoyl phosphate + PRPP aspartate + P_i + dihydroorotate
B)carbamoyl phosphate + aspartate + quinone Orotate + P_i + H₂O + reduced quinone
C)dihydroorotate + quinone orotate + reduced quinine
D)A and C
E)None of the above

Question 46

The anticancer drug methotrexate inhibits nucleotide synthesis.Which of the following explains why it also inhibits the synthesis of histidine and methionine?

A)The synthetic pathways for these amino acids require tetrahydrofolate for group transfer reactions.
B)These amino acids are derivatives of the nucleotides UTP and GTP.
C)Without the synthesis of nucleotides,there is not sufficient energy for the synthesis of the amino acids.
D)E)all of the above

Question 47

Ribonecleotides Using the diagram above,answer questions 43 - 45.C may be used to represent either or both of the atoms labeled C.
Glycine contributes to the ring at position _____.

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

Question 48

Rank the additions to the rings in order of formation.

A)C,B,A,F,D,E
B)C,E,D,C,F,A,B
C)A,C ,D ,E ,F ,B
D)D,F,A,C,B,E
E)C,F,A,C,B ,E ,D

Question 49

Ribonecleotides Using the diagram above,answer questions 43 - 45.C may be used to represent either or both of the atoms labeled C.
Formate contributes to the ring at position _____.

A)A
B)B
C)D
D)B,D
E)F

Question 50

In animals,elevated levels of PRPP will

A)activate pyrimidine biosynthesis.
B)activate purine biosynthesis.
C)activate both pyrimidine and purine biosynthesis.
D)inhibit pyrimidine biosynthesis;activate purine biosynthesis.
E)inhibit purine biosynthesis;activate pyrimidine biosynthesis.