Metabolism — MCQs

A 31-year-old male with cirrhosis, dementia, and Parkinson-like symptoms is diagnosed with a hereditary metabolic disease resulting from the accumulation of a certain metal in various tissues. Impairment of which of the following elimination pathways is most likely responsible?

Researchers are investigating the effects of an Amazonian plant extract as a novel therapy for certain types of tumors. When applied to tumor cells in culture, the extract causes widespread endoplasmic reticulum stress and subsequent cell death. Further experiments show that the extract acts on an important member of a protein complex that transduces proliferation signals. When this protein alone is exposed to the plant extract, its function is not recovered by the addition of chaperones. Which type of bond is the extract most likely targeting?

A 66-year-old man is brought to the emergency department because of weakness of his left leg for the past 30 minutes. His pants are soaked with urine. He has hypertension and atrial fibrillation. His temperature is 37°C (98.6°F), pulse is 98/min, and blood pressure is 160/90 mm Hg. Examination shows equal pupils that are reactive to light. Muscle strength is 2/5 in the left lower extremity. Plantar reflex shows an extensor response on the left. Within one minute of the onset of this patient's symptoms, the cells in his right anteromedial cortical surface enlarge significantly. Which of the following is the most likely explanation of the described cellular change?

A 25-year-old woman comes to the emergency department because of a mild headache, dizziness, fatigue, and nausea over the past several hours. She has no history of serious illness and takes no medications. She lives in a basement apartment and uses a wood stove for heating. Her temperature is 36°C (96.8°F) and pulse is 120/min. Arterial blood gas analysis shows a carboxyhemoglobin level of 11% (N = < 1.5). Which of the following mechanisms is the underlying cause of this patient's symptoms?

A 34-year-old woman presents to the emergency department with prominent hypotension and tachycardia. On examination, she has a low central venous pressure and high cardiac output. Her temperature is 38.9°C (102.0°F). The physician suspects a bacterial infection with a gram-negative bacterium. Samples are sent to the lab. Meanwhile, high volumes of fluids were given, but the blood pressure did not improve. She was started on noradrenaline. At the biochemical level, a major reaction was induced as part of this patient’s presentation. Of the following vitamins, which one is related to the coenzyme that participates in this induced biochemical reaction?

A 26-year-old man comes to the physician for evaluation of fatigue, facial rash, hair loss, and tingling of his hands and feet. He has followed a vegetarian diet for the past 3 years and has eaten 8 raw egg whites daily for the past year in preparation for a bodybuilding competition. Physical examination shows conjunctival injections and a scaly, erythematous rash around the eyes and mouth. Laboratory studies show decreased activity of propionyl-coenzyme A carboxylase in peripheral blood lymphocytes. Which of the following substances is most likely to be decreased in this patient?

A 55-year-old man is evaluated in the clinic for several episodes of diarrhea during the past 2 months. He denies having fever or abdominal pain and states that his diarrhea has been getting worse despite the use of over-the-counter loperamide and bismuth compounds. Upon further questioning, he recalls having multiple episodes of a burning sensation in his neck and upper chest, associated with redness and flushing of his face, which lasted for a few seconds. Because of his hypertension and dyslipidemia, the man is taking amlodipine and following a low-calorie diet. Physical examination shows that the blood pressure is 129/89 mm Hg, the pulse rate is 78/min, the respiratory rate is 14/min, and the temperature is 36.6°C (98.0°F). His abdomen is lax with no tenderness or rigidity, and rectal examination shows no blood in the rectal vault. Cardiac auscultation reveals a 3/6 holosystolic murmur in the tricuspid area, which increases in intensity with inspiration. Altered metabolism of which of the following amino acids is most likely the explanation for this patient’s presentation?

A 5-year-old boy presents to a pediatric orthopedic surgeon for evaluation of spinal curvature. His primary care physician noticed during an annual checkup that the boy's shoulders were uneven, and radiograph revealed early onset scoliosis. His past medical history is significant for multiple fractures as well as short stature. Based on the early presentation of scoliosis and the unusual history of fractures, the surgeon orders further workup and discovers a genetic mutation in an extracellular protein. This protein exists in two different forms. The first is an insoluble dimer that is linked by disulfide bonds and links integrins to the extracellular matrix. The second is a soluble protein that assists with clotting. Based on these descriptions, which of the following proteins is most likely mutated in this patient?

A 7-day-old female newborn is brought to the physician because of lethargy, vomiting, poor feeding, and diarrhea for 4 days. She was born at 39 weeks' gestation. Vital signs are within normal limits. Bilateral cataracts and icterus are present. Examination shows jaundice of the skin, and the liver is palpated 5-cm below the right costal margin. Muscle tone is decreased in all extremities. Serum glucose concentration is 40 mg/dL. Which of the following metabolites is most likely to be increased in this patient?

An 18-month-old girl is brought to the pediatrician’s office for failure to thrive and developmental delay. The patient’s mother says she has not started speaking and is just now starting to pull herself up to standing position. Furthermore, her movement appears to be restricted. Physical examination reveals coarse facial features and restricted joint mobility. Laboratory studies show increased plasma levels of several enzymes. Which of the following is the underlying biochemical defect in this patient?