What is the main function of red blood cells?

Red blood cells, also known as erythrocytes, have the primary function of transporting oxygen from the lungs to the tissues and carrying carbon dioxide from the tissues back to the lungs for exhalation. The presence of hemoglobin, a protein within red blood cells, is crucial for this process as it binds to oxygen molecules in the lungs and facilitates their delivery throughout the body.

Given this context, the primary role of red blood cells in gas exchange highlights their essential function in maintaining the body's metabolism and homeostasis. While other components of blood, such as white blood cells, play a role in fighting infections, and platelets are involved in blood clotting, these processes are not the main function of red blood cells.