Inner mitochondrial membrane
Components of a typical mitochondrion
The inner mitochondria membrane (IMM) is the mitochondrial membrane which separates the mitochondrial matrix from the intermembrane space.
The structure of the inner mitochondrial membrane is highly complex. The folds in the membrane are organized into cristae, which significantly increase the total surface area of the membrane. The membranes create two compartments. The intermembrane space, is the region between the inner and outer membranes.
The inner membrane of mitochondria is similar in lipid composition to the membrane of bacteria. This phenomenon can be explained by the endosymbiont hypothesis of the origin of mitochondria as prokaryotes internalized by a eukaryotic host cell.
In pig heart mitochondria, phosphatidylethanolamine makes up the majority of the inner mitochondrial membrane at 37.0% of the phospholipid composition. Phosphatidylcholine makes up about 26.5%, cardiolipin 25.4%, and phosphatidylinositol 4.5%. In S. cerevisiae mitochondria, phosphatidylcholine makes up 38.4% of the IMM, phosphatidylethanolamine makes up 24.0%, phosphatidylinositol 16.2%, cardiolipin 16.1%, phosphatidylserine 3.8%, and phosphatidic acid 1.5%.
The inner membrane is freely permeable only to oxygen, carbon dioxide, and water. It is much less permeable to ions and small molecules than the outer membrane, creating compartments by separating the matrix from the cytosolic environment. This compartmentalization is a necessary feature for metabolism. The inner mitochondrial membrane is both an electrical insulator and chemical barrier. Sophisticated ion transporters exist to allow speciﬁc molecules to cross this barrier. There are several antiport systems embedded in the inner membrane, allowing exchange of anions between the cytosol and the mitochondrial matrix.
- ATP–ADP translocase
- ATP-binding cassette transporter
- Cholesterol side-chain cleavage enzyme
- Protein tyrosine phosphatase
- Carnitine O-palmitoyltransferase
- Carnitine O-acetyltransferase
- Carnitine O-octanoyltransferase
- Cytochrome P450
- Translocase of the inner membrane
- Glutamate aspartate transporter
- Pyrimidine metabolism
- Mitochondrial inner membrane (55 proteins) Orientations of Proteins in Membranes (OPM) database
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- Lomize, Andrel; Lomize, Mikhail; Pogozheva, Irina (2013). "Membrane Protein Lipid Composition Atlas". Orientations of Proteins in Membranes. University of Michigan. Retrieved 10 April 2014.
- Krauss, Stefan (2001). "Mitochondria: Structure and Role in Respiration". Nature Publishing Group. Retrieved 9 April 2014.