Repeated USMLE Questions Step 1- Review- 348

Q- Deficiency of the enzyme argininosuccinate in the urea cycle leads to the accumulation of which one of the following?

A- Arginine

B- Argininosuccinate

C- Citrulline

D- Ornithine

C- Citrulline- Argininosuccinate synthetase deficiency (a urea cycle disorder) causes citrulline accumulation, because citrulline cannot be converted to argininosuccinate.

Q- Epinephrine acts on which one of the following receptors to constrict vascular smooth muscle?

A- α1-Adrenoceptors

B- α2-Adrenoceptors

C- β1-Adrenoceptors

D- β2-Adrenoceptors

A- α1-Adrenoceptors- Epinephrine causes vascular smooth muscle constriction primarily by stimulating α₁-adrenergic receptors.

Q- Which of the following is the most prominent side effect of scopolamine?

A- Bradycardia

B- Miosis

C- Mydriasis

D- Profuse sweating

C- Mydriasis- Scopolamine is an anticholinergic drug, and its prominent side effect is mydriasis, often accompanied by blurred vision due to cycloplegia.