a hemoprotein composed of globin and heme that gives red blood cells their characteristic color; function primarily to transport oxygen from the lungs to the body tissues
"fish have simpler hemoglobin than mammals"
The iron-containing substance in red blood cells that transports oxygen from the lungs to the rest of the body; it consists of a protein (globulin), and haem (a porphyrin ring with an atom of iron at its centre).
"The doctor explained that low levels of hemoglobin were causing her fatigue because there wasn't enough iron in her red blood cells to transport oxygen effectively."