A 65-year-old man with a long-standing history of chronic obstructive pulmonary disease (COPD) presents to his physician with worsening shortness of breath and fatigue. He reports that his symptoms have progressively worsened over the past few months, and he now struggles to perform daily activities like walking short distances or climbing stairs. On examination, his oxygen saturation is 85% on room air, and arterial blood gas (ABG) analysis reveals hypoxemia (PaO₂ = 60 mmHg) with a normal pH. His physician explains that his symptoms are due to impaired oxygen delivery, which is influenced by hemoglobin’s ability to bind and release oxygen. The physician further explains that hemoglobin’s quaternary structure plays a critical role in optimizing oxygen delivery to tissues. Which of the following best explains how hemoglobin’s quaternary structure enhances oxygen delivery to tissues?
