Question 1

Allopurinol can cure gouty arthritis because it inhibits the enzyme:

Accepted Answer

A) Adenosine deaminase. 
B) Thymidine kinase. 
C) Ribonucleotide reductase. 
D) Thymidylate synthase. 
E) Xanthine oxidase. 
A) Adenosine deaminase. 
B) Thymidine kinase. 
C) Ribonucleotide reductase. 
D) Thymidylate synthase. 
E) Xanthine oxidase. E

Question 2

A 1-year-old boy is brought to the pediatrician because his parents have noticed that he is mutilating himself by chewing on his lips.On examination, the child is found to be mentally retarded, and tophi are present in the earlobes.Which of the following enzymes is most likely deficient in this child?

Accepted Answer

A) Adenosine deaminase. 
B) Hypoxanthine-guanine phosphoribosyltransferase. 
C) Phosphoribosylpyrophosphate synthetase. 
D) Xanthine oxidase. 
E) Thymidylate kinase. 
A) Adenosine deaminase. 
B) Hypoxanthine-guanine phosphoribosyltransferase. 
C) Phosphoribosylpyrophosphate synthetase. 
D) Xanthine oxidase. 
E) Thymidylate kinase. B

Question 3

Fluorouracil is a uracil analog used in the treatment of malignant disorders.It reacts covalently with which one of the following enzymes, causing irreversible inhibition?

Accepted Answer

A) Phosphoribosyl pyrophosphate aminotransferase. 
B) Ribonucleotide reductase. 
C) Thymidylate synthase. 
D) Dihydrofolate reductase. 
E) Adenosine deaminase. 
A) Phosphoribosyl pyrophosphate aminotransferase. 
B) Ribonucleotide reductase. 
C) Thymidylate synthase. 
D) Dihydrofolate reductase. 
E) Adenosine deaminase. C

Question 4

The effect of the chemotherapeutic drug methotrexate is best described as:

Accepted Answer

A) Disruption of the mitotic spindle. 
B) Impaired synthesis of deoxyribonucleotides from ribonucleotides. 
C) Inhibition of orotic acid synthesis in the biosynthetic pathway of pyrimidine nucleotides. 
D) Depletion of tetrahydrofolate. 
E) Induction of mutations by DNA methylation. 
A) Disruption of the mitotic spindle. 
B) Impaired synthesis of deoxyribonucleotides from ribonucleotides. 
C) Inhibition of orotic acid synthesis in the biosynthetic pathway of pyrimidine nucleotides. 
D) Depletion of tetrahydrofolate. 
E) Induction of mutations by DNA methylation.

Question 5

Amethopterin (methotrexate) and fluorouracil are two drugs that are sometimes used in combination for cancer chemotherapy.Which of the following processes is inhibited by both of these drugs?

Accepted Answer

A) Reduction of ribonucleotides to deoxyribonucleotides. 
B) Synthesis of purine nucleotides. 
C) De novo synthesis of pyrimidine nucleotides. 
D) Synthesis of thymine. 
E) Polymerization of tubulin. 
A) Reduction of ribonucleotides to deoxyribonucleotides. 
B) Synthesis of purine nucleotides. 
C) De novo synthesis of pyrimidine nucleotides. 
D) Synthesis of thymine. 
E) Polymerization of tubulin.

Question 6

A 1-year-old boy has a history of recurrent bacterial and fungal infections.Further testing shows increased concentrations of deoxyadenosine triphosphate (dATP) in white blood cells.Which of the following is the most likely diagnosis?

Accepted Answer

A) Adenosine deaminase deficiency. 
B) Lesch-Nyhan syndrome. 
C) Orotic aciduria. 
D) Purine-nucleoside phosphorylase deficiency. 
E) Xanthine oxidase deficiency. 
A) Adenosine deaminase deficiency. 
B) Lesch-Nyhan syndrome. 
C) Orotic aciduria. 
D) Purine-nucleoside phosphorylase deficiency. 
E) Xanthine oxidase deficiency.

Question 7

For cancer patients, folic acid deficiency can be a good thing because the cancer cells need folate coenzymes for rapid DNA replication.Which of the following cancer chemotherapeutic agents induces a deficiency of folate coenzymes?

Accepted Answer

A) Methotrexate. 
B) Actinomycin D. 
C) Asparaginase. 
D) Azaserine. 
E) Colchicine. 
A) Methotrexate. 
B) Actinomycin D. 
C) Asparaginase. 
D) Azaserine. 
E) Colchicine.

Question 8

A 4-year-old girl presents in the clinic with megaloblastic anemia and failure to thrive.Orotic acid is demonstrated in blood and urine.Enzyme measurements of white blood cells reveal a deficiency of orotate phosphoribosyl transferase and abnormally high activity of aspartate transcarbamoylase.Which one of the following treatments will reverse all these symptoms?

Accepted Answer

A) Blood transfusion. 
B) White blood cell transfusion. 
C) Dietary supplements of phosphoribosylpyrophosphate. 
D) Oral thymidine. 
E) Oral uridine. 
A) Blood transfusion. 
B) White blood cell transfusion. 
C) Dietary supplements of phosphoribosylpyrophosphate. 
D) Oral thymidine. 
E) Oral uridine.

Allopurinol can cure gouty arthritis because it inhibits the enzyme:

Fluorouracil is a uracil analog used in the treatment of malignant disorders.It reacts covalently with which one of the following enzymes, causing irreversible inhibition?

The effect of the chemotherapeutic drug methotrexate is best described as:

Amethopterin (methotrexate) and fluorouracil are two drugs that are sometimes used in combination for cancer chemotherapy.Which of the following processes is inhibited by both of these drugs?

A 1-year-old boy has a history of recurrent bacterial and fungal infections.Further testing shows increased concentrations of deoxyadenosine triphosphate (dATP) in white blood cells.Which of the following is the most likely diagnosis?

For cancer patients, folic acid deficiency can be a good thing because the cancer cells need folate coenzymes for rapid DNA replication.Which of the following cancer chemotherapeutic agents induces a deficiency of folate coenzymes?

Introduction to Biomolecules

Introduction to Protein Structure

Oxygen Transporters: Hemoglobin and Myoglobin

Enzymatic Reactions

Coenzymes

DNA, RNA, and Protein Synthesis

The Human Genome

Protein Targeting

Introduction to Genetic Diseases

Viruses

DNA Technology

Biological Membranes

The Cytoskeleton

The Extracellular Matrix

Plasma Proteins

Extracellular Messengers

Intracellular Messengers

Cellular Growth Control and Cancer

Digestive Enzymes

Introduction to Metabolic Pathways

Glycolysis, Tricarboxylic Acid Cycle, and Oxidative Phosphorylation

Carbohydrate Metabolism

The Metabolism of Fatty Acids and Triglycerides

The Metabolism of Membrane Lipids

Lipid Transport

Amino Acid Metabolism

Heme Metabolism

Vitamins and Minerals

Integration of Metabolism

Filters

Exam 28: The Metabolism of Purines and Pyrimidines

Allopurinol can cure gouty arthritis because it inhibits the enzyme:

Fluorouracil is a uracil analog used in the treatment of malignant disorders.It reacts covalently with which one of the following enzymes, causing irreversible inhibition?

The effect of the chemotherapeutic drug methotrexate is best described as:

Amethopterin (methotrexate) and fluorouracil are two drugs that are sometimes used in combination for cancer chemotherapy.Which of the following processes is inhibited by both of these drugs?

A 1-year-old boy has a history of recurrent bacterial and fungal infections.Further testing shows increased concentrations of deoxyadenosine triphosphate (dATP) in white blood cells.Which of the following is the most likely diagnosis?

For cancer patients, folic acid deficiency can be a good thing because the cancer cells need folate coenzymes for rapid DNA replication.Which of the following cancer chemotherapeutic agents induces a deficiency of folate coenzymes?

Introduction to Biomolecules

Introduction to Protein Structure

Oxygen Transporters: Hemoglobin and Myoglobin

Enzymatic Reactions

Coenzymes

DNA, RNA, and Protein Synthesis

The Human Genome

Protein Targeting

Introduction to Genetic Diseases

Viruses

DNA Technology

Biological Membranes

The Cytoskeleton

The Extracellular Matrix

Plasma Proteins

Extracellular Messengers

Intracellular Messengers

Cellular Growth Control and Cancer

Digestive Enzymes

Introduction to Metabolic Pathways

Glycolysis, Tricarboxylic Acid Cycle, and Oxidative Phosphorylation

Carbohydrate Metabolism

The Metabolism of Fatty Acids and Triglycerides

The Metabolism of Membrane Lipids

Lipid Transport

Amino Acid Metabolism

Heme Metabolism

Vitamins and Minerals

Integration of Metabolism

Filters