Notably, the inner mitochondrial membrane is folded into numerous cristae (see diagram above), which expand the surface area of the inner mitochondrial membrane, enhancing its ability to generate ATP.
A mitochondrion (plural mitochondria) is an organelle found in most eukaryotic cells.
When the energy needs of a cell are high, mitochondria grow and divide.
A mutation in the genes regulating any of these functions can result in a variety of mitochondrial diseases.
When the energy use is low, mitochondria become inactive or are destroyed.
Mitochondrial genes are not inherited by the same mechanism as nuclear genes.
Sometimes new mitochondria are synthesized in centers that are rich in proteins and polyribosomes needed for their synthesis.
The egg itself contains relatively few mitochondria, but it is these mitochondria that survive and divide to populate the cells of the adult organism.
Mitochondria replicate their DNA and divide mainly in response to the energy needs of the cell—their growth and division is not linked to the cell cycle.
Mitochondrial genes are transcribed as multigenic transcripts that are cleaved and polyadenylated to yield mature mRNAs.
The primary function of mitochondria is to convert organic materials into cellular energy in the form of ATP.
The matrix contains a highly concentrated mixture of hundreds of enzymes, in addition to the special mitochondrial ribosomes, transfer RNA (tRNA), and several copies of the mitochondrial DNA genome.
Mitochondria are sometimes described as "cellular power plants," because their primary function is to convert organic materials into energy in the form of ATP via the process of oxidative phosphorylation.
Under certain conditions, protons may be allowed to re-enter the mitochondrial matrix without contributing to ATP synthesis.
The endosymbiotic hypothesis suggests that mitochondria descended from specialized bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm.
Mitochondria divide by binary fission similar to bacterial cell division.
During cell division, mitochondria are distributed to the daughter cells more or less randomly during the division of the cytoplasm.
Each pyruvate molecule produced by glycolysis is actively transported across the inner mitochondrial membrane, and into the matrix where it is combined with coenzyme A to form acetyl CoA.
Mitochondria of cells that have greater demand for ATP, such as muscle cells, contain even more cristae than typical liver mitochondria.
Mitochondrial ribosomes are the 70S (bacterial) type, in contrast to the 80S ribosomes found elsewhere in the cell.
Mitochondria have their own DNA, and, according to the generally accepted endosymbiotic theory, they were originally derived from external organisms.
At fertilization of an egg, a single sperm enters the egg along with the mitochondria that it uses to provide the energy needed for its swimming behavior.
A few groups of unicellular eukaryotes lack mitochondria: the symbiotic microsporidians, metamonads, and entamoebids, and the free-living pelobionts.
The study team compared the differences between the mitochondrial DNA of all the sampled individuals.
Outside the mitochondria, cells can generate ATP in the absence of oxygen; this process is called glycolysis.
Inside the mitochondria, however, much more energy is extracted.
Usually a cell has hundreds or thousands of mitochondria, which can occupy up to 25 percent of the cell's cytoplasm.
Some mitochondrial functions are performed only in specific types of cells.
Studies of mitochondrial DNA, which is circular and employs a variant genetic code, suggest their ancestor was a member of the Proteobacteria (Futuyma 2005), and probably related to the Rickettsiales.
In 1987, Rebecca Cann of the University of Hawaii compared mitochondrial DNA sampled from women whose ancestors came from different parts of the world.
Function. The most prominent roles of mitochondria are to produce the energy currency of the cell, ATP (i.e., phosphorylation of ADP), through respiration, and to regulate cellular metabolism. The central set of reactions involved in ATP production are collectively known as the citric acid cycle, or the Krebs cycle.