A 33-year-old woman is brought to the emergency department 30 minutes after being rescued from a fire in her apartment. She reports nausea, headache, and dizziness. Physical examination shows black discoloration of her oral mucosa. Pulse oximetry shows an oxygen saturation of 99% on room air. The substance most likely causing symptoms in this patient primarily produces toxicity by which of the following mechanisms?
AInhibition of mitochondrial complex V
BDegradation of 2,3-bisphosphoglycerate
COxidation of Fe2+
DRise in serum pH
ECompetitive binding to heme
A 25-year-old male athlete undergoes a cardiopulmonary exercise test. As exercise intensity increases from rest to moderate levels, which of the following best describes the relationship between oxygen consumption and cardiac output?
ALinear increase until anaerobic threshold
BExponential increase throughout exercise
CPlateau at low exercise intensities
DNo change until anaerobic threshold
A 24-year-old professional athlete is advised to train in the mountains to enhance his performance. After 5 months of training at an altitude of 1.5 km (5,000 feet), he is able to increase his running pace while competing at sea-level venues. Which of the following changes would produce the same effect on the oxygen-hemoglobin dissociation curve as this athlete's training did?
ADecreased 2,3-bisphosphoglycerate
BIncreased carbon monoxide inhalation
CDecreased temperature
DDecreased pH
EIncreased partial pressure of oxygen
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