Outer mitochondrial membrane: Difference between revisions
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{{component of organelle|mitochondrion}} | |||
==Definition== | ==Definition== | ||
The '''outer mitochondrial membrane''' is the ''outer'' membrane of the [[mitochondrion]], an [[organelle]] found in most [[eukaryotic cell]]s. It is an example of a [[biological membrane]]. It comprises a [[lipid bilayer]] along with various [[integral membrane protein]]s embedded in that bilayer. It helps control the entry and exit of materials between the mitochondrion on the inside | The '''outer mitochondrial membrane''' is the ''outer'' membrane of the [[mitochondrion]], an [[organelle]] found in most [[eukaryotic cell]]s. It is an example of a [[biological membrane]]. It comprises a [[lipid bilayer]] along with various [[integral membrane protein]]s embedded in that bilayer. It helps control the entry and exit of materials between the mitochondrion on the inside and the [[cytoplasm]] that surrounds it on the outside. The immediate inside side of the outer mitochondrial membrane is the [[intermembrane space of mitochondrion]]. | ||
The mitochondrion also has an [[inner mitochondrial membrane]] which is ''also'' a lipid bilayer; the intermembrane space separates the outer and inner mitochondrial membranes. | The mitochondrion also has an [[inner mitochondrial membrane]] which is ''also'' a lipid bilayer; the intermembrane space separates the outer and inner mitochondrial membranes. | ||
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| Number of outer mitochrondrial membranes per cell || Same as the number of mitochondria: 1 to 1000s, depending on the energy needs of the cell | | Number of outer mitochrondrial membranes per cell || Same as the number of mitochondria: 1 to 1000s, depending on the energy needs of the cell | ||
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| Size || <math>60 - 75</math> angstrom thickness, compared with mitochondrial | | Size || <math>60 - 75</math> angstrom thickness, compared with mitochondrial tubular radius of <math>0.5 - 1.0 \mu m</math> and length of <math>1 - 4 \mu m</math>, so the thickness is about 1% of the length of the mitochondrion. | ||
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| Location within mitochondrion || The outer mitochondrial membrane fully encloses the mitochondrion. | | Location within mitochondrion || The outer mitochondrial membrane fully encloses the mitochondrion. | ||
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| | | What's on both sides of it || The outside is the [[cytoplasm]], i.e., the rest of the cell (and more specifically, the [[cytosol]]). The inside is the [[intermembrane space of mitochondrion]], that separates the outer and inner mitochondrial membranes. | ||
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| Chemical constituents || Phosopholipids and [[integral membrane protein]]s called [[porin]]s | | Structural components || Similar to any [[biological membrane]], it has a [[lipid bilayer]] (comprising phospholipids) as well as large numbers of [[integral membrane protein]]s called [[porin]]s. | ||
|- | |||
| Chemical constituents || Phosopholipids and [[integral membrane protein]]s called [[porin]]s; the ratio is about 1:1 by weight, similar to the [[cell membrane]]. | |||
|- | |||
| Evolutionary origin || According to the [[endosymbiotic theory of mitochondrial origin]], the mitochondrion descends from endosymbiotic prokaryotes inside the eukaryotic cell. The outer mitochondrial membrane correspondingly descends from a membrane created by the host cell to firewall the endosymbiont's access to the rest of the cell. | |||
|- | |||
| Control of the entry and exit of materials || The outer mitochondrial membrane pretty freely allows small molecules to pass through, so the intermembrane space has a similar chemical composition as the [[cytosol]]. Large molecules are not allowed. | |||
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==Size and shape== | |||
{{size measures backgrounder}} | |||
===Thickness as a lipid bilayer=== | |||
The outer mitochondrial membrane is a [[biological membrane]], with its main piece (that defines its thickness) being a [[lipid bilayer]]. Lipid bilayers in general look like this; there are two lipids stacked up, so that the total thickness is the sum of the thicknesses of the two layers, which in turn are the diameters of the associated lipid molecules. | |||
[[File:Lipid bilayer section.gif]] | |||
Latest revision as of 01:42, 20 April 2024
This article describes a component of the organelle mitochondrion in cells.
Unless otherwise specified, information about this component is about its in situ occurrence in vivo, i.e., its occurrence in its usual location in living cells.
Definition
The outer mitochondrial membrane is the outer membrane of the mitochondrion, an organelle found in most eukaryotic cells. It is an example of a biological membrane. It comprises a lipid bilayer along with various integral membrane proteins embedded in that bilayer. It helps control the entry and exit of materials between the mitochondrion on the inside and the cytoplasm that surrounds it on the outside. The immediate inside side of the outer mitochondrial membrane is the intermembrane space of mitochondrion.
The mitochondrion also has an inner mitochondrial membrane which is also a lipid bilayer; the intermembrane space separates the outer and inner mitochondrial membranes.
Summary
| Item | Value |
|---|---|
| Type of organisms whose cells contain the outer mitochondrial membrane | Same as the organisms whose cells contain mitochondria: eukaryotic cells only, including plant cells, animal cells, and the cells of protists and fungi |
| Type of cells within the organisms that contain the outer mitochondrial membrane | Same as the cells that contain mitochondria: all cells except red blood cells in mammals (other vertebrates do have mitochondria in their red blood cells). |
| Number of outer mitochrondrial membranes per cell | Same as the number of mitochondria: 1 to 1000s, depending on the energy needs of the cell |
| Size | angstrom thickness, compared with mitochondrial tubular radius of and length of , so the thickness is about 1% of the length of the mitochondrion. |
| Location within mitochondrion | The outer mitochondrial membrane fully encloses the mitochondrion. |
| What's on both sides of it | The outside is the cytoplasm, i.e., the rest of the cell (and more specifically, the cytosol). The inside is the intermembrane space of mitochondrion, that separates the outer and inner mitochondrial membranes. |
| Structural components | Similar to any biological membrane, it has a lipid bilayer (comprising phospholipids) as well as large numbers of integral membrane proteins called porins. |
| Chemical constituents | Phosopholipids and integral membrane proteins called porins; the ratio is about 1:1 by weight, similar to the cell membrane. |
| Evolutionary origin | According to the endosymbiotic theory of mitochondrial origin, the mitochondrion descends from endosymbiotic prokaryotes inside the eukaryotic cell. The outer mitochondrial membrane correspondingly descends from a membrane created by the host cell to firewall the endosymbiont's access to the rest of the cell. |
| Control of the entry and exit of materials | The outer mitochondrial membrane pretty freely allows small molecules to pass through, so the intermembrane space has a similar chemical composition as the cytosol. Large molecules are not allowed. |
Size and shape
BACKGROUND INFORMATION ON SIZE MEASURES: Size measures for items related to cells (explains the units and orders of magnitude for various sizes)| Relation between ratios of lengths, areas, and volumes (a general geometric fact relating figures of similar shape and different sizes)
Thickness as a lipid bilayer
The outer mitochondrial membrane is a biological membrane, with its main piece (that defines its thickness) being a lipid bilayer. Lipid bilayers in general look like this; there are two lipids stacked up, so that the total thickness is the sum of the thicknesses of the two layers, which in turn are the diameters of the associated lipid molecules.
