Original: Hemoglobin has an oxygen binding capacity of 1.34 ml O2 per gram of hemoglobin , which increases the total blood oxygen capacity seventyfold compared to dissolved oxygen in blood . The mammalian hemoglobin molecule can bind ( carry ) up to four oxygen molecules .
Simplified: Hemoglobin ( also spelled hemoglobin ) is a protein in the blood which contains Iron and is used to transport oxygen around the body .