Metabolism — MCQs

During normal respiration in the lungs, oxygen is absorbed into the bloodstream and carbon dioxide is released. The oxygen is used in cells as the final electron acceptor during oxidative phosphorylation, and carbon dioxide is generated during each turn of the tricarboxylic citric acid cycle (TCA). Which of the following steps in the TCA cycle represents the first decarboxylation reaction that generates carbon dioxide?

A 46-year-old man presents to the emergency room after an industrial accident at a plastic manufacturer with altered consciousness, headache, shortness of breath, and abdominal pain. The vital signs include: blood pressure 145/80 mm Hg, heart rate 111/min, respiratory rate 27/min, and temperature 37.0℃ (98.6℉). The blood oxygen saturation on room air is 97%. On physical examination, the patient has a GCS score of 13. The skin is cherry-red and covered with perspiration. Breath and heart sounds are decreased. There is widespread tenderness on abdominal palpation. Blood testing shows the following findings: pH 7.29 Po2 66 mm Hg Pco2 30 mm Hg Na+ 144 mEq/L K+ 5.1 mEq/L Cl- 107 mEq/L HCO3- 11 mEq/L Base Excess -5 mEq/L Lactate 22 mmol/L (198.2 mg/dL) Inhibition of which enzyme caused this patient’s condition?

A 46-year-old man comes to the physician for a follow-up examination. He has type 2 diabetes mellitus and hypertension. Current medications include metformin and lisinopril. He reports that he has adhered to his diet and medication regimen. His hemoglobin A1c is 8.6%. Insulin glargine is added to his medication regimen. Which of the following sets of changes is most likely to occur in response to this new medication? $$$ Glycolysis %%% Glycogenesis %%% Lipolysis %%% Gluconeogenesis $$$

An investigator is studying heme biosynthesis in developing erythroid cells. After selective destruction of hemoglobin molecules, it is found that certain cells are unable to regenerate new heme molecules. A lack of which of the following structures would most likely explain this observation?

A 56-year-old man presents to his primary care doctor to discuss his plans for diet and exercise. He currently has hypertension treated with thiazide diuretics but is otherwise healthy. On exam, his temperature is 98.8°F (37.1°C), blood pressure is 122/84 mmHg, pulse is 70/min, and respirations are 12/min. His weight is 95.2 kilograms and his BMI is 31.0 kg/m^2. The patient is recommended to follow a 2000 kilocalorie diet with a 30:55 caloric ratio of fat to carbohydrates. Based on this patient’s body mass index and weight, he is recommended to consume 75 grams of protein per day. Which of the following represents the approximate number of grams of carbohydrates the patient should consume per day?

A 29-year-old female presents to the family physician concerned over the blue-black discoloration of her sclera and skin. She notes that at the end of her day, there are black stains in her underwear. The incomplete breakdown of which of the following amino acids is responsible for this presentation?

Two days after undergoing porcine aortic valve replacement surgery for aortic valve stenosis, a 62-year-old patient develops yellow discoloration of the sclera. His vital signs are within normal limits. Physical examination shows scleral icterus. Abdominal examination shows no abnormalities. Laboratory studies show: Hematocrit 49% Reticulocyte count 1.2% Serum AST 15 U/L ALT 18 U/L Bilirubin, total 2.8 mg/dL Direct 0.3 mg/dL Lactate dehydrogenase 62 U/L Which of the following is the most likely underlying mechanism of this patient's laboratory findings?

A 21-year-old man presents to the emergency department with acute back pain. The pain began a few hours prior to presentation and is located on the left lower back. The pain is described to be “shock-like,” 9/10 in pain severity, and radiates to the left groin. His temperature is 98.6°F (37°C), blood pressure is 120/75 mmHg, pulse is 101/min, and respirations are 18/min. The patient appears uncomfortable and is mildly diaphoretic. There is costovertebral angle tenderness and genitourinary exam is unremarkable. A non-contrast computerized tomography (CT) scan of the abdomen and pelvis demonstrates an opaque lesion affecting the left ureter with mild hydronephrosis. Straining of the urine with urine crystal analysis is demonstrated. Which of the following amino acids is most likely poorly reabsorbed by this patient’s kidney?

A 66-year-old man weighing 50 kg (110 lb) is admitted to the hospital because of sepsis complicated by acute respiratory distress syndrome. The physician decides to initiate total parenteral nutrition and prescribes short-term hypocaloric intake of 20 kcal/kg/day with 20% of the total energy requirement provided by proteins and 30% provided by fats. The physician calculates that a total volume of 1100 mL/day should be infused during the parenteral nutrition therapy to maintain fluid balance. A colloid containing 10 g/dL of albumin and an emulsion with a fat concentration of 33 g/dL are used to prepare parenteral nutrition modules. Which of the following is the most appropriate module to meet the carbohydrate requirement in this patient over the next 24 hours?

A newborn undergoing the standard screening tests is found to have a positive test for reducing sugars. Further testing is performed and reveals that the patient does not have galactosemia, but rather is given a diagnosis of fructosuria. What levels of enzymatic activity are altered in this patient?