Stores iron in a soluble, non-toxic, readily available form. Important for iron homeostasis. Iron is taken up in the ferrous form and deposited as ferric hydroxides after oxidation. Oligomer of 24 subunits. The functional molecule is roughly spherical and contains a central cavity into which the polymeric mineral iron core is deposited. There are three types of ferritin subunits in amphibia: L, M and H chains. M and H chains are fast mineralizing; the L chain is very slow mineralizing. Belongs to the ferritin family.