These subunits form a structure with a hollow cavity that can sequester 4500 atoms of iron. The iron can enter and exit the ferritin cavity and is part of the metabolic pool of reactive metals in the cell. Iron is necessary for enzyme function and in the mitochondria. The ferritin complexes are continually being recycled within the cell. Lyosomes are organelles within the cell that sequester and detoxify cellular material that could damage the cell.
Ferritin complexes combine together to form even larger complexes that are engulfed by the lyosomes.
Once in the lyosomes, the ferritin is converted to hemosiderin, a stable and non-reactive mixture of iron, protein and lipid. The iron is in a non-reactive state and not readily available to the cell. Ascrobic acid decreases the migration of ferritin complexes to the lyosomes, thus directly increasing the amount of ferritin-sequestered iron in the cell and indirectly the reactive iron, since iron can then move out of the ferritin molecule. Some tissues such as myocardium in the heart have a limited ability to make ferritin. Therefore it has less ability to sequester any free iron released into the body to prevent it from depositing in and damaging the heart.