Blood is made up of three parts: oxygen-carrying red cells, white blood cells, and plasma. Hemoglobin is a protein found within the red cells. One of the functions of hemoglobin is to carry oxygen from the lungs to the cells, tissues, and organs of the body, where it is released in order to burn nutrients for the production of energy. Once oxygen has been released, the resultant carbon dioxide is collected by hemoglobin and returned to the lungs, which exhale the excess.
