The main role of hemoglobin in the blood is to transport oxygen from the lungs to the tissues and carry carbon dioxide back from the tissues to the lungs. Hemoglobin binds to oxygen molecules in the lungs and releases them in areas with lower oxygen concentrations. This process is vital for maintaining healthy cell function and supporting metabolic activities throughout the body. Adequate levels of hemoglobin are crucial; deficiencies can lead to conditions such as anemia, which impairs oxygen transport.