A 4-day-old male newborn delivered at 39 weeks' gestation is evaluated because of poor feeding, recurrent vomiting, and lethargy. Physical examination shows tachypnea with subcostal retractions. An enzyme assay performed on a liver biopsy specimen shows decreased activity of carbamoyl phosphate synthetase I. This enzyme plays an important role in the breakdown and excretion of amino groups that result from protein digestion. Which of the following is an immediate substrate for the synthesis of the molecule needed for the excretion of amino groups?
AN-acetylglutamate
BHomocysteine
CPhenylalanine
DValine
EAspartate
An investigator is studying the activity level of several different enzymes in human subjects from various demographic groups. An elevated level of activity of phosphoribosyl pyrophosphate synthetase is found in one of the study subjects. This patient is most likely to have which of the following conditions?
APhenylketonuria
BHomocystinuria
CGout
DAlkaptonuria
EMaple syrup urine disease
A 26-year-old African American man comes to the physician because of a 3-day history of fatigue, back pain, and dark urine. One week ago, he developed a headache and was treated with aspirin. He does not smoke or use illicit drugs. Physical examination shows conjunctival pallor. A peripheral blood smear shows erythrocytes with inclusions of denatured hemoglobin. Which of the following enzymes is involved in providing precursors for nucleotide synthesis in this patient?
AGlucose-6-phosphatase
BCarbamoyl phosphate synthetase I
CPyruvate carboxylase
DTransaldolase
EEnolase
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