Question 1

A 1-year-old child with mental retardation has a deficiency of dihydrobiopterin reductase.This enzyme deficiency leads to an increased blood level of:

Accepted Answer

A)  Tyrosine.
B)  Methionine.
C)  Glucocerebroside.
D)  Glycine.
E)  Phenylalanine.F) All of the above
G) A) and D)

Question 2

The nitrogen balance is likely to be positive:

Accepted Answer

A)  In a professional boxer who retired from boxing and daily training 2 months ago.
B)  In a patient with arthritis who has recently been prescribed high doses of cortisol.
C)  In a person living on a diet that is deficient in methionine but otherwise contains enough protein.
D)  Three days after the last meal.
E)  During recovery from a severe infectious illness.F) D) and E)
G) C) and D)

Question 3

Quantitatively, the major metabolic fate of glycine in the body is:

Accepted Answer

A)  Conversion to serine by addition of a one-carbon unit from tetrahydrofolate.
B)  Transamination and oxidation to oxalic acid.
C)  Cleavage to carbon dioxide, ammonia, and a one-carbon group on tetrahydrofolate.
D)  Use for heme biosynthesis by d-aminolevulinate synthetase.
E)  Use for the synthesis of pyrimidine nucleotides.F) B) and D)
G) All of the above

Question 4

High homocysteine levels are associated with an increased risk of atherosclerosis.A deficiency of which of the following enzymes would result in high blood levels of homocysteine (and also methionine) ?

Accepted Answer

A)  Tyrosine hydroxylase.
B)  Cystathionine synthase.
C)  Threonine dehydratase.
D)  Glutathione reductase.
E)  L-Amino acid oxidase.F) B) and C)
G) A) and E)

Question 5

A 2-week-old infant presents with vomiting, lethargy, and convulsions without evidence of an infectious process.Laboratory examination reveals hyperammonemia without acidosis.The diagnosis is a hereditary deficiency of N-acetylglutamate synthetase.N-acetylglutamate is an allosteric activator of:

Accepted Answer

A)  Arginase.
B)  Carbamoyl-phosphate synthetase I.
C)  Arginosuccinate lyase.
D)  Ornithine transcarbamoylase.
E)  Arginosuccinate synthetase.F) B) and C)
G) A) and B)

Question 6

A nurse notices that the urine produced by a newborn infant has the odor of maple syrup.Which of the following pathways is most likely defective?

Accepted Answer

A)  Metabolism of branched-chain amino acids.
B)  Metabolism of aromatic amino acids.
C)  Metabolism of sulfur-containing amino acids.
D)  Transformation of carbohydrates to amino acids.
E)  One-carbon transfer reactions.F) A) and B)
G) A) and D)

Question 7

A newborn with acute encephalopathy is found to have hypoglycemia and ketonuria.Plasma leucine, isoleucine, and valine levels are markedly elevated, but the plasma ammonia level is normal.This is most likely a case of:

Accepted Answer

A)  Ornithine transcarbamoylase deficiency.
B)  Long-chain acyl-coenzyme A (Co
A)   dehydrogenase deficiency.
C)  Methylmalonic acidemia.
D)  Vitamin B12 deficiency.
E)  Maple syrup urine disease.F) B) and E)
G) A) and E) E

Question 8

A 2-week-old infant presents with vomiting, lethargy, and convulsions without evidence of an infectious process.Laboratory examination reveals hyperammonemia with alkalosis.Glutamine, citrulline, and arginine levels are found elevated in the blood.The enzyme that is most likely deficient in this patient is:

Accepted Answer

A)  Arginase.
B)  Carbamoyl-phosphate synthetase I.
C)  Arginosuccinate lyase.
D)  Ornithine transcarbamoylase.
E)  Arginosuccinate synthetase.F) None of the above
G) A) and B)

Question 9

A negative nitrogen balance is most likely to be present in:

Accepted Answer

A)  A heavyweight boxer training for the world championship.
B)  A fast-growing teenager who eats 3500 calories of junk food every day.
C)  A political prisoner who went on a hunger strike.
D)  A woman who is 8 months pregnant.
E)  A patient who is recovering from successful cancer surgery and chemotherapy.F) B) and E)
G) B) and C) C

Question 10

Coconut protein is biologically inferior because it is lacking many essential amino acids.In your efforts to make transgenic coconuts with protein of high biological value, you should definitely ensure that your coconut protein has an adequate amount of:

Accepted Answer

A)  Glutamine.
B)  Arginine.
C)  Phenylalanine.
D)  Tyrosine.
E)  Serine.F) A) and E)
G) B) and D) C

Exam 26: Amino Acid Metabolism

A 1-year-old child with mental retardation has a deficiency of dihydrobiopterin reductase.This enzyme deficiency leads to an increased blood level of:

Correct Answer
verified

The nitrogen balance is likely to be positive:

Correct Answer
verified

Quantitatively, the major metabolic fate of glycine in the body is:

Correct Answer
verified

High homocysteine levels are associated with an increased risk of atherosclerosis.A deficiency of which of the following enzymes would result in high blood levels of homocysteine (and also methionine) ?

Correct Answer
verified

A 2-week-old infant presents with vomiting, lethargy, and convulsions without evidence of an infectious process.Laboratory examination reveals hyperammonemia without acidosis.The diagnosis is a hereditary deficiency of N-acetylglutamate synthetase.N-acetylglutamate is an allosteric activator of:

Correct Answer
verified

A nurse notices that the urine produced by a newborn infant has the odor of maple syrup.Which of the following pathways is most likely defective?

Correct Answer
verified

A newborn with acute encephalopathy is found to have hypoglycemia and ketonuria.Plasma leucine, isoleucine, and valine levels are markedly elevated, but the plasma ammonia level is normal.This is most likely a case of:

Correct Answer
verified
E

Correct Answer
verified

A negative nitrogen balance is most likely to be present in:

Correct Answer
verified
C

Coconut protein is biologically inferior because it is lacking many essential amino acids.In your efforts to make transgenic coconuts with protein of high biological value, you should definitely ensure that your coconut protein has an adequate amount of:

Correct Answer
verified
C

Exam 26: Amino Acid Metabolism

A 1-year-old child with mental retardation has a deficiency of dihydrobiopterin reductase.This enzyme deficiency leads to an increased blood level of:

Correct AnswerverifiedShow Answer

The nitrogen balance is likely to be positive:

Correct AnswerverifiedShow Answer

Quantitatively, the major metabolic fate of glycine in the body is:

Correct AnswerverifiedShow Answer

High homocysteine levels are associated with an increased risk of atherosclerosis.A deficiency of which of the following enzymes would result in high blood levels of homocysteine (and also methionine) ?

Correct AnswerverifiedShow Answer

A 2-week-old infant presents with vomiting, lethargy, and convulsions without evidence of an infectious process.Laboratory examination reveals hyperammonemia without acidosis.The diagnosis is a hereditary deficiency of N-acetylglutamate synthetase.N-acetylglutamate is an allosteric activator of:

Correct AnswerverifiedShow Answer

A nurse notices that the urine produced by a newborn infant has the odor of maple syrup.Which of the following pathways is most likely defective?

Correct AnswerverifiedShow Answer

A newborn with acute encephalopathy is found to have hypoglycemia and ketonuria.Plasma leucine, isoleucine, and valine levels are markedly elevated, but the plasma ammonia level is normal.This is most likely a case of:

Correct AnswerverifiedE

Correct AnswerverifiedShow Answer

A negative nitrogen balance is most likely to be present in:

Correct AnswerverifiedC

Coconut protein is biologically inferior because it is lacking many essential amino acids.In your efforts to make transgenic coconuts with protein of high biological value, you should definitely ensure that your coconut protein has an adequate amount of:

Correct AnswerverifiedC

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
E

Correct Answer
verified

Correct Answer
verified
C

Correct Answer
verified
C