What ensures the transportation of oxygen in the blood?

Hemoglobin is a protein found in red blood cells that is crucial for the transportation of oxygen in the blood. Its structure allows it to bind to oxygen molecules in the lungs, where oxygen concentration is high. Once it binds to oxygen, hemoglobin carries this oxygen through the bloodstream to the tissues and organs that require it for metabolism. This binding occurs through a reversible process, enabling hemoglobin to release oxygen in areas where it is needed, such as tissues with lower oxygen tension. The role of hemoglobin is vital in maintaining sufficient oxygen levels in the body, which is essential for cellular respiration and overall health.

The other options—leukocytes (white blood cells), plasma (the liquid component of blood), and thrombocytes (platelets)—have different functions. Leukocytes are primarily involved in the immune response, plasma serves as a transport medium for various substances in the body, and thrombocytes play a key role in blood clotting.