MITOCHONDRIAL SRUCTURE
Mitochondria can be seen in the light microscope, but their detailed internal structure is only revealed by electron microscopy.
As ubiquitous, semi-autonomous cellular organelles, mitochondria are separated from the cytoplasm by the outer and inner mitochondrial membrane.The outer membrane is porous and freely traversed by ions and small, uncharged molecules through pore-forming membrane proteins (porins), such as the voltage-dependent anion channel VDAC [19]. Any larger molecules, especially proteins, have to be imported by special translocases. Because of its porosity, there is no membrane potential across the outer membrane. By contrast, the inner membrane is a tight diffusion barrier to all ions and molecules. These …show more content…
The innermost compartment, surrounded by the inner membrane, is the mitochondrial matrix(pH 7.9-8)The high pH of the mitochondrial matrix creates the trans-membrane electrochemical gradient that drives ATP synthesis The mitochondrial matrix is the site of organellar DNA replication, transcription, protein biosynthesis and numerous enzymatic reactions. Mitochondrial DNA is compacted by the mitochondrial transcription factor TFAM into supramolecular assemblies called nucleoids, of which there are about 1000 per cell [21]. Nucleoids are roughly spherical, with a diameter of ~100 nm, each containing one copy of mitochondrial DNA [22]. Mitochondrial ribosomes are membrane-attached, as their only products (in human cells) are hydrophobic membrane protein subunits, which integrate directly into the inner membrane upon …show more content…
This is the ~20 nm gap between the outer membrane and the part of the inner membrane that is known as the inner boundary membrane. All matrix proteins imported into the mitochondrion from the cytoplasm must pass through the outer and inner membrane and therefore also through the intermembrane space. Protein translocases of the outer (TOM) and inner (TIM) membrane form a TOM/TIM supercomplex which spans the intermembrane space and appears to be held together by the polypeptide in transit. The inner boundary membrane must contain large numbers of the carrier proteins that shuttle ions, ATP, ADP and small metabolites between the cytoplasm and the matrix. These small membrane proteins include most notably the 33 kDa ATP/ADP carrier [27], as well as numerous other related and unrelated membrane
Mitochondria can be seen in the light microscope, but their detailed internal structure is only revealed by electron microscopy.
As ubiquitous, semi-autonomous cellular organelles, mitochondria are separated from the cytoplasm by the outer and inner mitochondrial membrane.The outer membrane is porous and freely traversed by ions and small, uncharged molecules through pore-forming membrane proteins (porins), such as the voltage-dependent anion channel VDAC [19]. Any larger molecules, especially proteins, have to be imported by special translocases. Because of its porosity, there is no membrane potential across the outer membrane. By contrast, the inner membrane is a tight diffusion barrier to all ions and molecules. These …show more content…
The innermost compartment, surrounded by the inner membrane, is the mitochondrial matrix(pH 7.9-8)The high pH of the mitochondrial matrix creates the trans-membrane electrochemical gradient that drives ATP synthesis The mitochondrial matrix is the site of organellar DNA replication, transcription, protein biosynthesis and numerous enzymatic reactions. Mitochondrial DNA is compacted by the mitochondrial transcription factor TFAM into supramolecular assemblies called nucleoids, of which there are about 1000 per cell [21]. Nucleoids are roughly spherical, with a diameter of ~100 nm, each containing one copy of mitochondrial DNA [22]. Mitochondrial ribosomes are membrane-attached, as their only products (in human cells) are hydrophobic membrane protein subunits, which integrate directly into the inner membrane upon …show more content…
This is the ~20 nm gap between the outer membrane and the part of the inner membrane that is known as the inner boundary membrane. All matrix proteins imported into the mitochondrion from the cytoplasm must pass through the outer and inner membrane and therefore also through the intermembrane space. Protein translocases of the outer (TOM) and inner (TIM) membrane form a TOM/TIM supercomplex which spans the intermembrane space and appears to be held together by the polypeptide in transit. The inner boundary membrane must contain large numbers of the carrier proteins that shuttle ions, ATP, ADP and small metabolites between the cytoplasm and the matrix. These small membrane proteins include most notably the 33 kDa ATP/ADP carrier [27], as well as numerous other related and unrelated membrane