Stores iron in a soluble, non-toxic, readily available form. Important for iron homeostasis. Has ferroxidase activity. Iron is taken up in the ferrous form and deposited as ferric hydroxides after oxidation (By similarity). 4 Fe(2+) + 4 H(+) + O2 = 4 Fe(3+) + 2 H2O Oligomer of 12 or 24 subunits. The functional molecule is roughly spherical and contains a central cavity into which the polymeric mineral iron core is deposited (By similarity). Expressed in somatic tissues but not in oocytes. Belongs to the ferritin family.