Crista 200195 216178136 2008-05-31T12:53:57Z Arcadian 104523 wik {{otheruses}} [[Image:Mitochondrie.svg|thumb|300px|right|Mitochondria structure : <br/>1) [[Inner membrane]] <br/>2) [[Outer membrane]] <br/>3) Crista <br/>4) [[Matrix (biology)|Matrix]]]] '''Cristae''' (singular '''crista''') are the internal compartments formed by the [[Inner mitochondrial membrane|inner membrane]] of a [[mitochondrion]]. They are studded with proteins, including [[ATP synthase]] and a variety of [[cytochrome]]s. The maximum surface for chemical reactions to occur is within the mitochondria. This allows [[cellular respiration]] ([[aerobic respiration]] since the mitochondria requires oxygen) to occur. == Electron transport chain of the cristae == [[NADH]] is split into [[NAD+|NAD<sup>+</sup>]], H<sup>+</sup> [[ions]], and [[electrons]] by an [[enzyme]]. [[Flavin|FADH<sub>2</sub>]] is also split into H<sup>+</sup> ions, electrons, and [[FAD]]. As those [[electron]]s travel further through the [[electron transport chain]] in the inner membrane, energy is gradually released and used to pump the hydrogen ions from the splitting of NADH and FADH<sub>2</sub> into the space between the inner membrane and the outer membrane (called the [[intermembrane space]]), creating an [[electrochemical gradient]]. As a result, [[chemiosmosis]] occurs, producing [[Adenosine triphosphate|ATP]] from [[Adenosine diphosphate|ADP]] and a [[phosphate group]] when [[ATP synthase]] harnesses the [[potential energy]] from the concentration gradient formed by the amount of H<sup>+</sup> ions. H<sup>+</sup> ions passively pass into the mitochondrian [[matrix (biology)|matrix]] by the ATP synthase, and later on help to reform H<sub>2</sub>O. The [[electron transport chain]] requires a constant supply of electrons in order to properly function and generate ATP. However, the electrons that have entered the electron transport chain would eventually pile up like cars traveling down a one-way dead-end street. Those electrons are finally accepted by [[oxygen]] (O<sub>2</sub>), which combine with some of the hydrogen ions from the mitochondrian matrix through [[ATP synthase]] and the electrons that had traveled through the electron transport chain. As a result they form two molecules of [[water]] (H<sub>2</sub>O). By accepting the electrons, oxygen allows the electron transport chain to continue functioning. The electrons from each NADH molecule can form a total of 2.5 ATPs from ADPs and phosphate groups through the electron transport chain, while each FADH<sub>2</sub> molecule can produce a total of 1.5 ATPs. As a result, the 10 NADH molecules (from [[glycolysis]] and the [[Krebs cycle]]) and the 2 FADH<sub>2</sub> molecules can form a total of 34 ATPs from this electron transport chain during [[aerobic respiration]]. This means that combined with the Krebs Cycle and [[glycolysis]], the efficiency for the electron transport chain is about 65%, as compared to only 3.5% efficiency for glycolysis alone. ==Usefulness== The cristae greatly increase the surface area on which the above mentioned reactions take place. If they were absent, the inner membrane would be reduced to a single [[sphere|spherical]] [[shape]], and with less reaction surface available, the reaction efficiency would be likewise reduced. Therefore, cristae are a necessity for the [[mitochondria]] to function efficiently. [[Category:Cellular respiration]] [[Category:Membrane biology]] [[ca:Cresta mitocondrial]] [[de:Crista]] [[lt:Kristos]] [[tr:Krista]]