A 55-year-old man with a history of gout presents to the clinic with recurrent joint pain and swelling in his big toe. His condition is linked to an imbalance between purine and pyrimidine nucleotide synthesis. His physician explains that nucleotide biosynthesis is regulated by allosteric effectors, including ATP and CTP, which influence the enzyme aspartate transcarbamoylase (ATCase). Which of the following best describes the regulation of ATCase?
A 32-year-old male presents with muscle weakness and fatigue. Blood tests reveal elevated serine levels. Further investigations show reduced activity of 3-phosphoglycerate dehydrogenase, an enzyme involved in serine biosynthesis. The inhibition of this enzyme is likely due to feedback regulation by serine. Which of the following best describes the mechanism of feedback inhibition?
A 35-year-old male with a history of type 2 diabetes presents to the endocrinology clinic for routine follow-up. He reports feeling fatigued and has difficulty maintaining stable blood glucose levels despite medication. Laboratory results show elevated fasting glucose, and his physician explains that hormonal signals, such as those involving cyclic adenosine monophosphate (cAMP), are critical in regulating glucose metabolism. The discussion turns to how enzymes in glycogen breakdown are controlled. In this patient with diabetes, which mechanism best describes how cyclic adenosine monophosphate (cAMP) rapidly regulates enzyme activity in glucose metabolism?
A 42-year-old man presents to the emergency department with a two-week history of worsening headaches, fever, and focal neurological deficits, including right-sided weakness and difficulty speaking. He reports a history of chronic sinusitis, which has been poorly managed over the years. He denies any recent trauma, surgeries, or systemic infections. On examination, he has a temperature of 38.9°C (102°F), nuchal rigidity, and right-sided hemiparesis. An MRI of the brain reveals a ring-enhancing lesion in the left frontal lobe, consistent with a brain abscess. Blood cultures are pending, and a lumbar puncture is deferred due to the risk of herniation. What is the most likely cause of this brain abscess?
A 45-year-old woman with type 2 diabetes mellitus presents to the clinic for routine follow-up. She is on metformin and insulin therapy. Laboratory tests reveal elevated fasting glucose levels despite medication adherence. Her physician explains that hormonal regulation of glucose metabolism involves second messengers that alter enzyme activity in response to external signals. Which of the following second messengers plays a key role in regulating glucose metabolism in response to hormonal signals?
A 25-year-old military recruit presents with acute onset of fever, sore throat, and swollen tonsils, with some white exudates. There’s a known outbreak of respiratory illness in his barracks.Which adenovirus serotype is most likely responsible for this respiratory outbreak?
A 3-year-old girl presents with 2 days of watery diarrhea, vomiting, and low-grade fever. She attends daycare, and several children have recently experienced similar symptoms. Stool PCR testing identifies adenovirus. Which adenovirus serotypes are most commonly associated with gastrointestinal symptoms?
A 3-year-old child presents with a high fever, cough, and conjunctivitis. The child’s mother mentions that several children in the daycare have had similar symptoms. Which of the following viruses is most likely responsible for this child’s symptoms?
A 62-year-old male with multiple myeloma, a cancer of plasma cells, is prescribed bortezomib, a proteasome inhibitor. The oncologist explains that bortezomib works by blocking the degradation of proteins involved in cell cycle regulation, leading to cancer cell death. The patient asks how inhibiting the proteasome specifically targets cancer cells while sparing normal cells. Based on the principles of the ubiquitin-proteasome pathway, which of the following best explains the mechanism of bortezomib in treating multiple myeloma?
A 60-year-old female patient with a history of multiple myeloma, a cancer characterized by abnormal plasma cells, is being treated with bortezomib, a drug that inhibits the 26S proteasome. After starting treatment, she experiences an accumulation of misfolded proteins in her cells, leading to improved control of her cancer but also side effects such as neuropathy. The physician explains that the drug targets a specific cellular process involved in protein degradation. Question: What is the primary role of the 26S proteasome, which is inhibited by bortezomib in this patient?
