What component is primarily responsible for carrying oxygen in the blood?

The primary component responsible for carrying oxygen in the blood is erythrocytes, or red blood cells (RBCs). These cells contain hemoglobin, a specialized protein that binds to oxygen molecules in the lungs and transports them to tissues throughout the body. The structure of erythrocytes—specifically their biconcave shape—maximizes their surface area, allowing for efficient gas exchange.

While plasma does carry some dissolved oxygen, it is not the main transporter and carries a significantly smaller amount compared to what erythrocytes can hold. White blood cells, which are part of the immune system, play no role in oxygen transport. Similarly, platelets are involved in blood clotting and do not contribute to oxygen delivery in the body. Thus, erythrocytes are uniquely equipped for the vital function of oxygen transport.