Editing Mitochondrion (section)

===Intermembrane space===
The '''mitochondrial intermembrane space''' is the space between the outer membrane and the inner membrane. It is also known as perimitochondrial space. Because the outer membrane is freely permeable to small molecules, the concentrations of small molecules, such as ions and sugars, in the intermembrane space is the same as in the [[cytosol]].<ref name="Alberts-2005"/> However, large proteins must have a specific signaling sequence to be transported across the outer membrane, so the protein composition of this space is different from the protein composition of the [[cytosol]]. One [[protein]] that is localized to the intermembrane space in this way is [[cytochrome c]].<ref name="Chipuk-2006"/>