SGrade/USMLE Step 1/Biochemistry and Molecular Biology — Core Concepts
Biochemistry and Molecular Biology — Core Concepts Practice Questions
This topic covers essential Biochemistry and Molecular Biology principles as tested in USMLE Step 1.
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A 28-year-old woman presents with muscle weakness and exercise intolerance. Genetic testing reveals a mutation affecting the succinate dehydrogenase enzyme. This enzyme is unique in the Krebs cycle because it is also a component of which of the following?
Examiner's Design Intent
Tests integration of metabolic pathways with electron transport, specifically knowledge that succinate dehydrogenase has dual identity as Krebs cycle enzyme and ETC Complex II
A newborn infant appears normal at birth but develops lethargy, vomiting, and seizures within the first 48 hours of life. Lab results show severe hyperammonemia and respiratory alkalosis. A defect in the urea cycle is suspected. Which of the following molecules serves as the primary nitrogen donor for the urea cycle?
Examiner's Design Intent
Tests precise understanding of urea cycle mechanism within clinical context of neonatal hyperammonemia - core Step 1 biochemistry application
A 4-month-old infant presents with lethargy, poor feeding, and hepatomegaly. Lab tests reveal hypoglycemia and lactic acidosis. Further investigation shows a deficiency in glucose-6-phosphatase. The accumulation of glucose-6-phosphate in the liver primarily directs glucose flux towards which of the following pathways?
Examiner's Design Intent
Tests understanding of metabolic flux redirection when key enzymes are deficient, specifically glucose-6-phosphatase in Von Gierke disease
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