Question 1

Xanthine oxidase catalyzes the formation of ________.

Accepted Answer

A) xanthine 
B) uric acid 
C) hypoxanthine 
D) xanthine and uric acid 
E) All of the above 
A) xanthine 
B) uric acid 
C) hypoxanthine 
D) xanthine and uric acid 
E) All of the above

Question 2

Substrates for reduction to form deoxyribonucleotides are

Accepted Answer

A) mononucleotides. 
B) trinucleotides. 
C) dinucleotides. 
D) B and C. 
E) All of the above. 
A) mononucleotides. 
B) trinucleotides. 
C) dinucleotides. 
D) B and C. 
E) All of the above.

Question 3

Which is the correct order for the synthesis of CTP?

Accepted Answer

A) UMP → UDP→ UTP → CTP 
B) GMP → GDP→ GTP → CTP 
C) UTP → TTP→ CTP 
D) UMP → CMP→ CDP → CTP 
A) UMP → UDP→ UTP → CTP 
B) GMP → GDP→ GTP → CTP 
C) UTP → TTP→ CTP 
D) UMP → CMP→ CDP → CTP

Question 4

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 5

The first step in the de novo biosynthesis of IMP is a reaction between glutamine and PRPP.Which statement is not true about this reaction?

Accepted Answer

A) An amine group is attached to the anomeric carbon atom of the ribose ring. 
B) The configuration of the anomeric carbon atom is inverted from β to α. 
C) A pyrophosphate is lost from PRPP. 
D) The reaction is catalyzed by glutamine-PRPP aminotransferase. 
A) An amine group is attached to the anomeric carbon atom of the ribose ring. 
B) The configuration of the anomeric carbon atom is inverted from β to α. 
C) A pyrophosphate is lost from PRPP. 
D) The reaction is catalyzed by glutamine-PRPP aminotransferase.

Question 6

About 3% of all deoxycytidylate residues in mammalian DNA are methylated after DNA is synthesized.

Accepted Answer

A) True 
 B)False

Question 7

The pyrimidine ring system is shown below.What is the source of the C-2 during the de novo biosynthesis of pyrimidines?

Accepted Answer

A) Aspartate. 
B) PRPP. 
C) Bicarbonate. 
D) Tetrahydrofolate. 
A) Aspartate. 
B) PRPP. 
C) Bicarbonate. 
D) Tetrahydrofolate.

Question 8

The reduction of ribonucleotides by ribonucleotide reductase requires the formation of a(n)________.

Accepted Answer

A) covalent intermediate 
B) free radical protein 
C) intermediate methyl group 
D) acid-base catalyst 
A) covalent intermediate 
B) free radical protein 
C) intermediate methyl group 
D) acid-base catalyst

Question 9

The pyrimidine ring system is shown below.What is the source of the N-1 during the de novo biosynthesis of pyrimidines?

Accepted Answer

A) Aspartate. 
B) Urea. 
C) Asparagine. 
D) IMP. 
A) Aspartate. 
B) Urea. 
C) Asparagine. 
D) IMP.

Question 10

No distinctive excretory products are formed from the catabolism of pyrimidines.

Accepted Answer

A) True 
 B)False

Question 11

In prokaryotes,carbamoyl phosphate is an intermediate in the de novo biosynthesis of pyrimidine nucleotides.

Accepted Answer

A) True 
 B)False

Question 12

The purine ring system is shown below.What is the source of the nitrogen atoms 3 and 9 during the de novo biosynthesis of purines?

Accepted Answer

A) Aspartate. 
B) Glycine. 
C) Arginine. 
D) Glutamine. 
A) Aspartate. 
B) Glycine. 
C) Arginine. 
D) Glutamine.

Question 13

The coenzyme biotin is required for the carboxylation of aminoimidazole ribonucleotide (AIR)during the de novo synthesis of IMP by the enzyme AIR carboxylase.

Accepted Answer

A) True 
 B)False

Question 14

The purine ring system is shown below.What is the source of the carbon atoms 2 and 8 during de novo biosynthesis of purines?

Accepted Answer

A) Carbon dioxide. 
B) Aspartate. 
C) 10-formyltetrahydrofolate. 
D) Glutamine. 
A) Carbon dioxide. 
B) Aspartate. 
C) 10-formyltetrahydrofolate. 
D) Glutamine.

Question 15

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 16

Pigs excrete guanine rather that further catabolizing it because ________.

Accepted Answer

A) deamination leads to a product toxic to pigs 
B) guanase is produced in extremely small amounts and is only activated under conditions of starvation 
C) guanine is a component of antibiotics fed to pigs to enhance their growth 
D) pigs lack the enzyme guanase 
A) deamination leads to a product toxic to pigs 
B) guanase is produced in extremely small amounts and is only activated under conditions of starvation 
C) guanine is a component of antibiotics fed to pigs to enhance their growth 
D) pigs lack the enzyme guanase

Question 17

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 18

In birds and reptiles,purine nucleotides and surplus nitrogen from amino acid catabolism is disposed of in the form of ________ while humans form that,as well as ________ in nitrogenous waste.

Accepted Answer

A) xanthine,uric acid 
B) uric acid;xanthine 
C) uric acid;urea 
D) urea;uric acid 
E) urea;guanine 
A) xanthine,uric acid 
B) uric acid;xanthine 
C) uric acid;urea 
D) urea;uric acid 
E) urea;guanine

Question 19

dCMP,dGMP,dAMP and dTMP are substrates for a reductase that phosphorylates them to the triphosphate levels for incorporation into DNA.

Accepted Answer

A) True 
 B)False

Question 20

Which is used to synthesize CTP?

Accepted Answer

A) CMP. 
B) GMP. 
C) TMP. 
D) UMP. 
A) CMP. 
B) GMP. 
C) TMP. 
D) UMP.

Exam 18: Nucleotide Metabolism

Xanthine oxidase catalyzes the formation of ________.

Substrates for reduction to form deoxyribonucleotides are

Which is the correct order for the synthesis of CTP?

Which is the correct order for the synthesis of dTMP?

The first step in the de novo biosynthesis of IMP is a reaction between glutamine and PRPP.Which statement is not true about this reaction?

About 3% of all deoxycytidylate residues in mammalian DNA are methylated after DNA is synthesized.

The pyrimidine ring system is shown below.What is the source of the C-2 during the de novo biosynthesis of pyrimidines?

The reduction of ribonucleotides by ribonucleotide reductase requires the formation of a(n)________.

The pyrimidine ring system is shown below.What is the source of the N-1 during the de novo biosynthesis of pyrimidines?

No distinctive excretory products are formed from the catabolism of pyrimidines.

In prokaryotes,carbamoyl phosphate is an intermediate in the de novo biosynthesis of pyrimidine nucleotides.

The purine ring system is shown below.What is the source of the nitrogen atoms 3 and 9 during the de novo biosynthesis of purines?

The coenzyme biotin is required for the carboxylation of aminoimidazole ribonucleotide (AIR)during the de novo synthesis of IMP by the enzyme AIR carboxylase.

The purine ring system is shown below.What is the source of the carbon atoms 2 and 8 during de novo biosynthesis of purines?

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

Pigs excrete guanine rather that further catabolizing it because ________.

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

In birds and reptiles,purine nucleotides and surplus nitrogen from amino acid catabolism is disposed of in the form of ________ while humans form that,as well as ________ in nitrogenous waste.

dCMP,dGMP,dAMP and dTMP are substrates for a reductase that phosphorylates them to the triphosphate levels for incorporation into DNA.

Which is used to synthesize CTP?

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

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

In birds and reptiles,purine nucleotides and surplus nitrogen from amino acid catabolism is disposed of in the form of while humans form that,as well as in nitrogenous waste.