USMLE styled question bank

1. Imagine you’re preparing for a long-distance marathon and need sustained energy throughout the race. Which of the following organs stores the maximum amount of glycogen that your body can use during prolonged exercise? A. Adipose tissue B. Cardiac muscle C. Kidney D. Liver E. Skeletal muscle   The correct answer is E. Skeletal muscle:

1. A researcher is investigating the effect of an enzyme whose reaction product is crucial for de novo fatty acid synthesis. Which of the following enzymes is most likely the focus of this study? A. Acyl CoA Dehydrogenase B. Glucose-6-Phosphatase C. Glucose-6-Phosphate Dehydrogenase (G-6PD) D. Lactate Dehydrogenase E. Phosphofructokinase-1 (PFK-1)   Correct Answer – C.

11. During fasting and feeding states, several enzymes are regulated to maintain glucose and energy homeostasis. Specific biochemical processes occur in an individual at rest who has fasted for 12 hours to adapt to the energy demand. Which of the following occurs in such a state? A. Phosphodiesterase is activated by insulin B. Pyruvate carboxylase

1. A 4-month-old boy is being evaluated for seizures, psychomotor retardation, and hypotonia. Work-up reveals elevated serum levels of lactate, alanine, pyruvate, and ketoacids. Based on the clinical presentation, pyruvate carboxylase activity is measured using fibroblasts from a skin biopsy and is found to be markedly decreased. This enzyme is normally used to directly synthesize

11. A 48-year-old patient is brought to the emergency room after exposure to toxic fumes suspected to contain cyanide. He presents with shortness of breath, confusion, and metabolic acidosis. The medical team suspects cyanide toxicity, which disrupts the electron transport chain (ETC). Which of the following statements concerning the components of the electron transport chain

1. The cytosolic isoform of which of the following TCA cycle enzymes requires NADP⁺ as a coenzyme, which can be utilized in the reduced state for reductive biosynthesis? A. Aconitase B. Citrate Synthase C. Isocitrate Dehydrogenase D. Malate Dehydrogenase E. Succinate Dehydrogenase The correct answer is C: Isocitrate Dehydrogenase: The cytosolic isoform of isocitrate dehydrogenase

1. A 24-year-old woman presents with diarrhea, dysphagia, jaundice, and white transverse lines on her fingernails (Mee’s lines). She is diagnosed with arsenic poisoning. Arsenic poisoning inhibits which of the following enzymes? A. Citrate synthase B. Isocitrate dehydrogenase C. Malate dehydrogenase D. Succinate dehydrogenase E. α-Keto glutarate dehydrogenase complex Correct answer: E. α-Keto glutarate dehydrogenase