Editing Ferrous (section)

==Ferrous ions in biology==
{{main article|Iron in biology}}
{{See also|Iron metabolism}}
All known forms of life require iron.<ref>{{cite web | title = Iron integral to the development of life on Earth – and the possibility of life on other planets | url = https://www.ox.ac.uk/news/2021-12-07-iron-integral-development-life-earth-and-possibility-life-other-planets | date = 7 December 2021 | publisher = [[University of Oxford]] | accessdate = 9 May 2022}}</ref> Many [[protein]]s in living beings contain iron(II) centers. Examples of such [[metalloprotein]]s include [[hemoglobin]], [[ferredoxin]], and the [[cytochrome]]s. In many of these proteins, Fe(II) converts reversibly to Fe(III).<ref>{{cite book |author=Berg, Jeremy Mark |author2=Lippard, Stephen J. |title=Principles of bioinorganic chemistry |publisher=University Science Books |location=Sausalito, Calif |year=1994 |isbn=0-935702-73-3 }}</ref>

Insufficient iron in the human diet causes [[anemia]]. Animals and humans can obtain the necessary iron from foods that contain it in assimilable form, such as meat. Other organisms must obtain their iron from the environment. However, iron tends to form highly insoluble iron(III) oxides/hydroxides in aerobic ([[oxygen]]ated) environment, especially in [[calcareous soil]]s. [[Bacteria]] and [[graminaceae|grass]]es can thrive in such environments by secreting compounds called [[siderophore]]s that form soluble complexes with iron(III), that can be reabsorbed into the cell. (The other plants instead encourage the growth around their roots of certain bacteria that [[redox|reduce]] iron(III) to the more soluble iron(II).)<ref name=marsch94>H. Marschner and V. Römheld (1994): "Strategies of plants for acquisition of iron". ''Plant and Soil'', volume 165, issue 2, pages 261–274. {{doi|10.1007/BF00008069}}</ref>[[File:Pourbaix Diagram of Iron.svg|thumb|[[Pourbaix diagram]] of aqueous iron]]In contrast to iron(III) aquo complexes, iron(II) aquo complexes are soluble in water near neutral pH.{{citation needed|date=April 2024}} Ferrous iron is, however, oxidized by the oxygen in air, converting to iron(III).<ref>{{cite encyclopedia|last=Petsch|first=S.T.|title=Treatise on Geochemistry|edition=Second|year=2014|volume=10|series=Reference Module in Earth Systems and Environmental Sciences|pages=437–473|isbn=978-0-08-095975-7|chapter=10.11 - The Global Oxygen Cycle|doi=10.1016/B978-0-08-095975-7.00811-1|editor-last1=Holland|editor-first1=H.D.|editor-last2=Turekian|editor-first2=K.K.|publisher=Elsevier}}</ref>