What is the primary role of hemoglobin in red blood cells?

The primary role of hemoglobin in red blood cells is to transport oxygen from the lungs to the tissues throughout the body. Hemoglobin is a specialized protein that binds to oxygen molecules, allowing red blood cells to efficiently carry oxygen via the bloodstream. Once the red blood cells reach the tissues, hemoglobin releases the oxygen, which is then utilized by cells for various metabolic processes.

The structure of hemoglobin enables it to pick up oxygen in the high-oxygen environment of the lungs and release it in the lower-oxygen environment of the body's tissues. This function is crucial for maintaining cellular respiration and ensuring that all body organs and tissues receive the oxygen they need to function properly.

While the other options mention functions related to the body's physiology, they do not pertain to hemoglobin's main role. For instance, fighting infection is primarily the role of white blood cells, digestion involves various enzymes and organs, and temperature regulation is managed through different mechanisms in the body, not specifically by hemoglobin.