Inner mitochondrial membrane

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Cell biology
The mitochondrion
Mitochondrion mini.svg
Components of a typical mitochondrion

1 Outer membrane

1.1 Porin

2 Intermembrane space

2.1 Intracristal space
2.2 Peripheral space

3 Lamella

3.1 Inner membrane   ◄ You are here
3.11 Inner boundary membrane
3.12 Cristal membrane
3.2 Matrix
3.3 Cristæ

4 Mitochondrial DNA
5 Matrix granule
6 Ribosome
7 ATP synthase


The inner mitochondria membrane (IMM) is the mitochondrial membrane which separates the mitochondrial matrix from the intermembrane space.

Structure[edit]

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.[1]

Composition[edit]

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%.[2] 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%.[3]

In the inner mitochondrial membrane, the protein-to-lipid ratio is 80:20, in contrast to the outer membrane, which is 50:50.[4]

Permeability[edit]

The inner membrane is freely permeable only to oxygen, carbon dioxide, and water.[1] 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.[4]

IMM-associated proteins[edit]

See also[edit]

External links[edit]

References[edit]

  1. ^ a b Caprette, David R. (12 December 1996). "Structure of Mitochondria". Experimental Biosciences. Rice University. Retrieved 9 April 2014. 
  2. ^ Comte J, Maïsterrena B, Gautheron DC (January 1976). "Lipid composition and protein profiles of outer and inner membranes from pig heart mitochondria. Comparison with microsomes". Biochim. Biophys. Acta 419 (2): 271–84. PMID 1247555. Retrieved 2014-04-09. 
  3. ^ Lomize, Andrel; Lomize, Mikhail; Pogozheva, Irina (2013). "Membrane Protein Lipid Composition Atlas". Orientations of Proteins in Membranes. University of Michigan. Retrieved 10 April 2014. 
  4. ^ a b Krauss, Stefan (2001). "Mitochondria: Structure and Role in Respiration". Nature Publishing Group. Retrieved 9 April 2014.