Editing Ferric (section)

==Iron(III) in biology==
All known forms of life require iron, which usually exists in Fe(II) or Fe(III) oxidation states.<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(III) centers.  Examples of such [[metalloprotein]]s include [[oxyhemoglobin]], [[ferredoxin]], and the [[cytochrome]]s.  Many organisms, from bacteria to humans, store iron as microscopic crystals (3 to 8 nm in diameter) of [[iron(III) oxide hydroxide]], inside  a shell of the protein [[ferritin]], from which it can be recovered as needed.<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>  

The insolubility of iron(III) compounds is also responsible for the low levels of iron in seawater, which is often the limiting factor for the growth of the microscopic plants ([[phytoplankton]]) that are the basis of the marine food web.<ref>{{cite journal |vauthors=Boyd PW, Watson AJ, Law CS |title=A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization |journal=Nature |volume=407 |issue=6805 |pages=695–702 |date=October 2000 |pmid=11048709 |doi=10.1038/35037500 |display-authors=etal|bibcode=2000Natur.407..695B |s2cid=4368261 }}</ref>

[[File:Pourbaix Diagram of Iron.svg|thumb|[[Pourbaix diagram]] of aqueous iron]]