A 30-year-old woman presents with muscle weakness and fatigue. Laboratory tests reveal elevated creatine kinase levels and myoglobinuria. Her physician suspects rhabdomyolysis and explains that myoglobin, a protein with a tertiary structure, is released from damaged muscle cells. The physician contrasts myoglobin’s structure with hemoglobin’s quaternary structure. Which of the following best describes the difference between hemoglobin and myoglobin in terms of protein structure and oxygen binding?
