Final answer:
The primary role of red blood cells is to transport oxygen through the blood, facilitated by hemoglobin, which binds to oxygen. A small amount of oxygen is carried by the plasma. White blood cells function in immunity, and platelets are critical for blood clotting.
Step-by-step explanation:
Transport of Oxygen in the Blood
The majority of oxygen in the blood is carried by red blood cells (RBCs) which contain the protein hemoglobin. Hemoglobin can bind up to four oxygen molecules, allowing each RBC to transport a large amount of oxygen from the lungs to the body's tissues. Although a small percentage of oxygen (1.5%) dissolves in the plasma, 98.5% is bound to hemoglobin in RBCs.
Red blood cells develop in the bone marrow and when mature, lack nuclei and mitochondria. Their primary function is to carry oxygen, facilitated by the iron-containing heme portion of hemoglobin. The binding of oxygen to the heme results in the formation of oxyhemoglobin, which gives blood its bright red color when oxygenated.
White blood cells (WBCs) are less numerous than RBCs and serve protective functions in the immune system, defending the body against pathogens, while platelets are cell fragments that play key roles in blood clotting.