Metabolism — MCQs

A 25-year-old woman presents to the emergency department for the evaluation of a severe abdominal pain of 5 hours duration. The pain is colicky but is not localized. She also complains of nausea and an episode of vomiting. For the past 2 days, she has been constipated. She has had similar episodes of varying intensity in the past that resolved over a few hours. Several laboratory tests and imaging studies have been conducted in the past which were all within normal limits. The medical history is otherwise unremarkable. She denies smoking cigarettes or drinking alcohol. The vital signs are as follows: pulse 100/min, respiratory rate 16/min, and blood pressure 138/84 mm Hg. The physical examination reveals a young woman in obvious distress. There is no tenderness on abdominal examination. Laboratory tests are ordered, analgesics are administered, and the patient was admitted overnight for observation. In the morning, a urine sample was shown to have darkened overnight. Abnormal levels of which of the following most likely led to this patient’s condition?

A 14-year-old boy is brought to the physician by his mother because of a 12-hour history of abdominal pain and dark urine. Three days ago, he developed a cough, sore throat, and rhinorrhea. Examination shows conjunctival pallor, scleral icterus, and mild splenomegaly. A peripheral blood smear shows small round inclusions within erythrocytes and several erythrocytes with semicircular indentations. The underlying cause of this patient's condition is most likely to also affect which of the following processes?

A 5-year-old boy is brought into your office by his mother. His father recently passed away, and his mother states she just lost her job. She has been unable to buy food regularly, and they have had to eat boiled and preserved vegetables. His mother denies that the boy has any prior medical conditions, but the patient states that his gums bleed when he brushes his teeth. On exam, the patient's vital signs are normal, but he appears malnourished. There is gum hypertrophy present on exam along with small, curled hairs over his head. CBC is significant for a Hgb of 9.5 g/dL with an MCV of 85. PT, aPTT, and bleeding time are all normal. What is the most likely cause?

An 82-year-old woman is brought to the emergency room after her neighbor saw her fall in the hallway. She lives alone and remarks that she has been feeling weak lately. Her diet consists of packaged foods and canned meats. Her temperature is 97.6°F (36.4°C), blood pressure is 133/83 mmHg, pulse is 95/min, respirations are 16/min, and oxygen saturation is 98% on room air. Physical exam is notable for a weak, frail, and pale elderly woman. Laboratory studies are ordered as seen below. Hemoglobin: 9.1 g/dL Hematocrit: 30% Leukocyte count: 6,700/mm^3 with normal differential Platelet count: 199,500/mm^3 MCV: 110 fL Which of the following is the most likely deficiency?

A graduate student at the biochemistry laboratory decides to research the different effects of vitamin deficiencies in mice by completely depriving the mice of one vitamin. The symptoms of this deficiency include posterior column and spinocerebellar tract demyelination, as well as hemolytic anemia. Further analysis is negative for megaloblastic anemia, hypersegmented neutrophils, and elevated serum methylmalonic acid. What characteristic of the vitamin is causing the symptoms in the mice?

A 25-year-old man presents to the emergency department with sudden-onset severe pain in the right shoulder that occurred when he threw a bowling ball 2 hours ago. He has a history of dislocations in both shoulders and subluxation of the right knee and left wrist. There is no history of fractures. On physical examination, the right arm is slightly abducted and externally rotated. An anterior bulge is seen near the shoulder joint. The neurovascular examination of the right arm shows no abnormalities. The skin examination shows multiple widened atrophic scars around the knees, elbows, and ankles. The skin of the neck and around the elbow can easily be extended up to 4 cm. The sclera is white. The remainder of the physical examination shows no abnormalities. A defect in which of the following proteins is the most likely cause of the findings in this patient?

A 24-year-old man comes to the physician with his wife because of difficulty conceiving during the past year. He emigrated from rural Romania 2 years ago and has a history of recurrent respiratory infections since childhood for which he has not sought treatment. Physical examination shows mild hepatomegaly and clubbing of the nail beds. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels are increased. Microscopic analysis of centrifuged seminal fluid shows no sperm cells. This patient's condition is most likely caused by impaired function of a channel protein that normally opens in response to binding of which of the following?

A 20-year-old male is brought by ambulance to the emergency room in extremis. He is minimally conscious, hypotensive, and tachypneic, and his breath gives off a "fruity" odor. An arterial blood gas and metabolic panel show anion gap metabolic acidosis. This patient is most likely deficient in which of the following metabolic actions?

A 55-year-old man with alcoholic cirrhosis is admitted to the hospital for routine evaluation before liver transplantation. The physician asks the patient to stop eating 10 hours before surgery. Which of the following structures contributes directly to preventing fasting hypoglycemia by producing glucose in this patient?

After being warned by the locals not to consume the freshwater, a group of American backpackers set off on a week-long hike into a region of the Ecuadorean Amazon forest known for large gold mines. The group of hikers stopped near a small stream and used the water they filtered from the stream to make dinner. Within the next half hour, the hikers began to experience headaches, vertigo, visual disturbances, confusion, tachycardia, and altered levels of consciousness. Which of the following enzymes was most likely inhibited in this group of hikers?