A 25-year-old male patient with a rare neurodegenerative disorder presents with tremors, cognitive decline, and protein aggregates in his brain tissue on autopsy. Genetic testing reveals a mutation affecting an E3 ligase involved in the ubiquitin-proteasome pathway, leading to the accumulation of misfolded proteins. Question: Which of the following best explains how a dysfunctional E3 ligase contributes to protein aggregation in this patient?
A 22-year-old college student presents with a sudden onset of red, painful eyes, photophobia, and watery discharge. He recently went swimming in a public pool. Examination reveals bilateral conjunctival injection and subepithelial corneal infiltrates. What is the most likely causative agent?
A 28-year-old researcher is studying bacterial enzyme regulation. She observes that Escherichia coli grown on glucose do not produce β-galactosidase unless lactose is added to the medium. This suggests that the enzyme is inducible and requires a stimulus for its synthesis. Which of the following best explains the regulation of β-galactosidase synthesis in E. coli?
A 5-year-old boy presents with a 3-day history of fever, sore throat, and red, watery eyes. He attends daycare where several other children have similar symptoms. On examination, he has pharyngeal erythema, bilateral conjunctival injection, and cervical lymphadenopathy. A rapid strep test is negative, and a viral PCR panel confirms adenovirus infection. Which condition is most consistent with this presentation?
A 65-year-old man with muscle wasting and fatigue is diagnosed with cachexia due to an underlying malignancy. Laboratory tests reveal increased muscle protein degradation. The physician explains that his condition is associated with excessive protein breakdown through the ubiquitin-proteasome pathway. Which of the following best describes how the ubiquitin-proteasome pathway regulates protein degradation?
A 60-year-old man with chronic obstructive pulmonary disease (COPD) presents with increasing shortness of breath and fatigue. Arterial blood gas (ABG) analysis shows: pH: 7.30 (Normal: 7.35–7.45) PCO₂: 55 mmHg (Normal: 35–45 mmHg) PO₂: 60 mmHg (Normal: 80–100 mmHg) Bicarbonate (HCO₃⁻): 28 mEq/L (Normal: 22–26 mEq/L) The patient is experiencing chronic respiratory acidosis due to CO₂ retention. Which of the following best describes how oxygen delivery to the tissues is affected in this patient?
A 35-year-old male with chronic obstructive pulmonary disease (COPD) presents with shortness of breath and fatigue. Arterial blood gas analysis shows hypoxemia (low PO₂), hypercapnia (elevated PCO₂), and acidosis (low pH). His condition affects oxygen binding and release from hemoglobin as he struggles to oxygenate his tissues effectively. Which of the following best contrasts the Haldane effect and the Bohr effect in this patient’s oxygen-hemoglobin dynamics?
A 55-year-old female with type 2 diabetes mellitus is prescribed metformin, a drug that lowers blood glucose levels by inhibiting gluconeogenesis in the liver. During a routine check-up, she asks how metformin specifically targets gluconeogenesis without affecting glycolysis, given that both pathways share several intermediates. Based on the principles of metabolic compartmentation and regulation, which of the following best explains how metformin selectively inhibits gluconeogenesis?
A 45-year-old woman with type 2 diabetes presents to her physician with fatigue and unexplained weight loss. Laboratory tests show elevated blood glucose levels and increased ketone bodies in her urine. Her physician explains that due to insufficient insulin signaling, her body is relying on fatty acid oxidation and gluconeogenesis for energy, leading to ketone production. Which of the following best explains why metabolic pathways, such as gluconeogenesis and fatty acid oxidation, continue to proceed in a unidirectional manner despite reversible reactions?
A 55-year-old man with a history of hyperlipidemia presents to his physician for a routine checkup. His recent blood tests reveal elevated LDL cholesterol levels. His physician prescribes a medication that inhibits HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis. Which of the following best describes the mechanism of this drug?
