What is the primary function of hemoglobin?

Hemoglobin's primary function is to transport oxygen from the lungs to the tissues and return carbon dioxide from the tissues to the lungs. It does this by binding to oxygen molecules in the lungs where the concentration of oxygen is high, and then releasing that oxygen to the cells in the body that need it for metabolism. As the oxygen is released, hemoglobin picks up carbon dioxide, a waste product of metabolism, from the tissues. This carbon dioxide is then transported back to the lungs, where it is exhaled.

This function is crucial for maintaining adequate oxygen levels in the body, which is essential for energy production and overall cellular function. While hemoglobin does have some secondary roles, such as minor participation in buffering blood pH, its primary and most significant role remains as an oxygen carrier. Other choices, although they refer to important physiological processes, do not accurately reflect the main function of hemoglobin in the body.