An erythrocyte is a cell without a nucleus and organelles; it contains only the cell membrane, a cytoskeleton and enzymes. It is composed of 97% of hemoglobin, which is a molecule that contains iron and has the oxygen-binding capacity. Erythrocytes are produced in the bone marrow and have an average life cycle of 120 days. A healthy adult has about 4 to 5 million erythrocytes per cubic millimeter of blood. If someone has less than that amount, it is said that he suffers from anemia, or is anemic, and must eat iron-rich food, such as red meat, eggs, and green vegatable.