Which cell type is primarily responsible for transporting oxygen in the blood?

• A. Platelets
• B. Erythrocytes
• C. Lymphocytes
• D. Monocytes

Answer: (B)

Oxygen transport in the blood is carried by red blood cells because they contain hemoglobin, a protein with iron that binds oxygen in the lungs and releases it to tissues where it’s needed. The distinctive biconcave shape of these cells increases surface area for gas exchange and allows efficient travel through tiny capillaries. Hemoglobin becomes highly saturated with oxygen in the lungs and releases it as blood reaches tissues with lower oxygen, enabling cells to use it for metabolism. Platelets are involved in clotting, while lymphocytes and monocytes are white blood cells focused on immune responses, not oxygen transport. In non-mammalian species the red blood cells may be nucleated, but their job of carrying oxygen through hemoglobin remains the primary function.