Editing Mitochondrion (section)

===Inner membrane===
{{Main|Inner mitochondrial membrane}}

The inner mitochondrial membrane contains proteins with three types of functions:<ref name="Alberts-2005"/>
# Those that perform the [[electron transport chain]] [[redox]] reactions
# [[ATP synthase]], which generates [[Adenosine triphosphate|ATP]] in the matrix
# Specific [[membrane transport protein|transport proteins]] that regulate [[metabolite]] passage into and out of the [[mitochondrial matrix]]

It contains more than 151 different [[polypeptide]]s, and has a very high protein-to-phospholipid ratio (more than 3:1 by weight, which is about 1&nbsp;protein for 15&nbsp;phospholipids). The inner membrane is home to around 1/5 of the total protein in a mitochondrion.<ref name="Schenkel-2014">{{cite journal | vauthors = Schenkel LC, Bakovic M | title = Formation and regulation of mitochondrial membranes | journal = International Journal of Cell Biology | volume = 2014 | pages = 709828 | date = January 2014 | pmid = 24578708 | pmc = 3918842 | doi = 10.1155/2014/709828 | doi-access = free }}</ref> Additionally, the inner membrane is rich in an unusual phospholipid, [[cardiolipin]]. This phospholipid was originally discovered in [[Bos taurus|cow]] hearts in 1942, and is usually characteristic of mitochondrial and bacterial plasma membranes.<ref name="McMillin-2002">{{cite journal | vauthors = McMillin JB, Dowhan W | title = Cardiolipin and apoptosis | journal = Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids | volume = 1585 | issue = 2–3 | pages = 97–107 | date = December 2002 | pmid = 12531542 | doi = 10.1016/S1388-1981(02)00329-3 }}</ref> Cardiolipin contains four fatty acids rather than two, and may help to make the inner membrane impermeable,<ref name="Alberts-2005"/> and its disruption can lead to multiple clinical disorders including neurological disorders and cancer.<ref>{{cite journal | vauthors = Bautista JS, Falabella M, Flannery PJ, Hanna MG, Heales SJ, Pope SA, Pitceathly RD | title = Advances in methods to analyse cardiolipin and their clinical applications | journal = Trends in Analytical Chemistry | volume = 157 | pages = 116808 | date = December 2022 | pmid = 36751553 | pmc = 7614147 | doi = 10.1016/j.trac.2022.116808 }}</ref> Unlike the outer membrane, the inner membrane does not contain porins, and is highly impermeable to all molecules. Almost all ions and molecules require special membrane transporters to enter or exit the matrix. Proteins are ferried into the matrix via the [[translocase of the inner membrane]] (TIM) complex or via [[OXA1L]].<ref name="Herrmann-2000"/> In addition, there is a membrane potential across the inner membrane, formed by the action of the [[enzyme]]s of the [[electron transport chain]]. Inner membrane [[mitochondrial fusion|fusion]] is mediated by the inner membrane protein [[OPA1]].<ref name="Youle-2012">{{cite journal | vauthors = Youle RJ, van der Bliek AM | title = Mitochondrial fission, fusion, and stress | journal = Science | volume = 337 | issue = 6098 | pages = 1062–1065 | date = August 2012 | pmid = 22936770 | pmc = 4762028 | doi = 10.1126/science.1219855 | bibcode = 2012Sci...337.1062Y }}</ref>

====Cristae====
[[File:MitochondrionCAM.jpg|thumb|250 px|right|Cross-sectional image of cristae in a [[rat]] liver mitochondrion to demonstrate the likely 3D structure and relationship to the inner membrane]]
{{Main|Crista}}

The inner mitochondrial membrane is compartmentalized into numerous folds called [[crista]]e, which expand the surface area of the inner mitochondrial membrane, enhancing its ability to produce ATP. For typical liver mitochondria, the area of the inner membrane is about five times as large as that of the outer membrane. This ratio is variable and mitochondria from cells that have a greater demand for ATP, such as muscle cells, contain even more cristae. Mitochondria within the same cell can have substantially different crista-density, with the ones that are required to produce more energy having much more crista-membrane surface.<ref name="Cserép-2018">{{cite journal | vauthors = Cserép C, Pósfai B, Schwarcz AD, Dénes Á | title = Mitochondrial Ultrastructure Is Coupled to Synaptic Performance at Axonal Release Sites | journal = eNeuro | volume = 5 | issue = 1 | pages = ENEURO.0390–17.2018 | date = 2018 | pmid = 29383328 | pmc = 5788698 | doi = 10.1523/ENEURO.0390-17.2018 }}</ref> These folds are studded with small round bodies known as [[F-ATPase|F{{sub|1}} particles]] or oxysomes.<ref name="Mannella-2006">{{cite journal | vauthors = Mannella CA | title = Structure and dynamics of the mitochondrial inner membrane cristae | journal = Biochimica et Biophysica Acta (BBA) - Molecular Cell Research | volume = 1763 | issue = 5–6 | pages = 542–548 | year = 2006 | pmid = 16730811 | doi = 10.1016/j.bbamcr.2006.04.006 | doi-access =  }}</ref>