What is the function of hemoglobin in red blood cells?

Hemoglobin is a vital protein found in red blood cells that primarily functions to transport oxygen from the lungs to the tissues of the body and to carry carbon dioxide, a waste product of metabolism, from the tissues back to the lungs for exhalation. The structure of hemoglobin allows it to bind oxygen efficiently; it contains iron that gives it the ability to pick up oxygen when red blood cells pass through the lungs, where oxygen concentration is high.

As red blood cells travel through the body, hemoglobin releases the oxygen to the tissues that need it for cellular respiration and energy production. Additionally, it binds carbon dioxide, facilitating its return to the lungs for removal from the body.

While other options mention functions like fighting infections or maintaining blood pressure, those functions are not performed by hemoglobin; they are managed by white blood cells and the cardiovascular system or other body mechanisms. Similarly, while pH regulation is an important bodily function, it involves multiple systems and does not directly relate to hemoglobin's primary role. Thus, the choice regarding hemoglobin's function in transporting oxygen and carbon dioxide is accurate and underscores its critical role in respiratory physiology.