View source for Red Blood Cells

==Composition==
Red blood cells contain the [[protein]] [[hemoglobin]], which contains [[iron]] as a [[coenzyme]], and enables the blood cells to reversibly bind oxygen in the bloodstream. Mammalian red blood cells lack a nucleus and, thus, contain no genetic material of their own. They also lack the machinery for protein synthesis.  The lifespan of a red blood cell is about 90 days. Dead and dying RBCs are broken down and disposed of in the spleen and the liver where the released iron is conserved for reuse in the synthesis of new red blood cells.