What is the primary function of hemoglobin?

The primary function of hemoglobin is to transport oxygen from the lungs to various tissues and organs throughout the body. Hemoglobin is a protein found in red blood cells, composed of heme groups that contain iron. This iron can bind to oxygen molecules, allowing hemoglobin to effectively carry oxygen.

When blood reaches the lungs, hemoglobin binds to oxygen molecules, forming oxyhemoglobin. As blood circulates through body tissues, hemoglobin releases the oxygen, making it available for cellular metabolism. This process is essential for sustaining life, as oxygen is a critical component in the production of energy within cells.

The other options do not accurately describe the primary role of hemoglobin. For instance, the role of fighting infections is primarily associated with immune cells such as white blood cells. Carrying nutrients is a function attributed to other components in the blood, like plasma proteins and blood plasma itself. Finally, aiding in digestion is a function primarily related to the gastrointestinal system, rather than a role of hemoglobin.