What is the main function of red blood cells (RBCs)?

The main function of red blood cells (RBCs) is to carry oxygen from the lungs to the tissues and to transport carbon dioxide from the tissues back to the lungs. This critical role is facilitated by hemoglobin, a specialized protein within RBCs that binds to oxygen in the lungs and releases it in the tissues where it is needed for cellular respiration. Likewise, hemoglobin also binds to carbon dioxide, which is a waste product of metabolism, and helps transport it back to the lungs for exhalation.

Oxygen transport is essential for maintaining the energy production processes in cells, and the removal of carbon dioxide is vital for maintaining the body's acid-base balance and preventing toxicity. This unique function of red blood cells is what distinguishes them from other components of blood, reflecting their primary role in respiratory gas exchange in the body.