USMLE 1- 50 Qs
2 Questions
| Attempts: 115
50 Qs from all topics of Step 1
Questions and Answers
- 1.
A 34-year-old female develops moderate hyperglycemia during her first pregnancy and is diagnosed with gestational diabetes mellitus. Her glycemic status improves markedly after delivery. She says that her mother and younger sister both had “high blood sugars” during pregnancy. If this patient’s gestational hyperglycemia is genetically predisposed, this patient is most likely to have decreased activity in which of the following enzymes?
- A.
Glucokinase
- B.
Phosphofructokinase
- C.
Aldolase
- D.
Pyruvate kinase
- E.
Enolase
Correct Answer
A. GlucokinaseExplanation
Glucokinase is a glucose sensor within pancreatic beta cells. Inactivating mutations of the enzyme result in mild hyperglycemia that can be exacerbated by pregnancy.Rate this question:
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- 2.
A newborn is diagnosed with hyperphenylalaninemia at birth and placed on a special phenylalanine-restricted diet. Several months later, the infant has a normal serum phenylalanine level; however, some neurological abnormalities are observed. His serum prolactin level is elevated. Which of the following enzymes is most likely deficient in this patient?
- A.
Phenylalanine hydroxylase
- B.
Dihydrobiopterin reductase
- C.
Dopamine hydroxylase
- D.
Homogentisate oxidase
- E.
N-methyltransferase
Correct Answer
C. Dopamine hydroxylaseExplanation
Tetrahydrobiopterin (BH4) is a cofactor used in the synthesis of tyrosine, dopa, serotonin, and nitric oxide. Initially, tyrosine is converted to DOPA by the enzyme tyrosine hydroxylase, with BH4 present as a cofactor. Next, DOPA is decarboxylated to dopamine by the enzyme DOPA carboxylase.Rate this question:
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Jan 09, 2013Quiz Edited by
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Jan 27, 2010Quiz Created by
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