What is the primary function of red blood cells?

The primary function of red blood cells (RBCs), also known as erythrocytes, is to transport oxygen (O2) from the lungs to the tissues throughout the body and to carry carbon dioxide (CO2), a waste product of metabolism, from the tissues back to the lungs for exhalation. This function is facilitated by hemoglobin, a protein found in red blood cells that binds to both oxygen and carbon dioxide.

The structure of red blood cells, which are biconcave discs without nuclei in mature cells, optimizes their capacity to carry gases. The large surface area relative to their volume allows for efficient gas exchange. The ability to transport these gases is crucial for maintaining proper physiological function, supporting cellular respiration, and managing acid-base balance in the bloodstream.

Other options do reference important functions within the body, but they pertain to different types of blood components or processes. For example, white blood cells play a crucial role in the immune response to protect against infections, platelets are vital for the clotting process, and plasma proteins and other components are responsible for transporting nutrients. However, none of these functions pertain directly to the primary role of red blood cells.