Describe How Hemoglobin Binds and Releases Oxygen

Hemoglobin (Hb) is a red, iron-containing respiratory pigment present in red blood cells. It plays a vital role in oxygen transport by reversibly binding with oxygen to form oxyhemoglobin (HbO₂).

Oxygen binding at the lungs:

• In the alveoli, where the partial pressure of oxygen (pO₂) is high (~100 mm Hg), hemoglobin combines with oxygen.
• Reaction: Hb + O₂ → HbO₂ (Oxyhemoglobin)
• This reaction occurs in the pulmonary capillaries where oxygen diffuses from alveolar air into the blood.

Oxygen release at tissues:

• In body tissues, where pO₂ is low (~40 mm Hg) and CO₂ levels are high, hemoglobin releases oxygen.
• Reaction: HbO₂ → Hb + O₂
• The released oxygen diffuses into the tissue cells for cellular respiration.

Thus, hemoglobin acts as a carrier and regulator of oxygen supply, binding oxygen in the lungs and releasing it in oxygen-deficient tissues.