How many oxygen molecules can each hemoglobin molecule carry at maximum?

Hemoglobin, the protein found in red blood cells, is specifically designed to transport oxygen throughout the body. Each hemoglobin molecule can bind to a maximum of four oxygen molecules. This is possible because hemoglobin consists of four subunits, each containing an iron atom that can each bind one oxygen molecule.

When hemoglobin binds oxygen in the lungs, it undergoes a conformational change that increases its affinity for additional oxygen molecules. As each oxygen binds, the hemoglobin molecule becomes increasingly saturated, allowing for efficient oxygen transport. This ability to carry four oxygen molecules enables hemoglobin to effectively meet the oxygen demands of tissues during physical activity and rest.

Thus, the answer that states hemoglobin can carry a maximum of four oxygen molecules is correct and reflects the structure and function of hemoglobin in the circulatory system.