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Cell Division - Mitochondria


Mitochondria Electron Micrograph

The organelles we call mitochondria are found in the cytoplasm of nearly all eukaryotic cells, and are passed down from mother cell to daughter cell.[1] Mitochondria have a separate replication and division rate to that of the normal cell division, but they do divide (fission) and fuse (fusion)[2]

The major role of mitochondria is to produce adenosine triphosphate (ATP). This is done by systematically extracting energy from nutrient molecules (substrates, such as fats and sugars). ATP is the universal energy-yielding commodity in cells, used by enzymes to perform a wide range of cellular functions. It is impossible for cells to survive, even for a moment, without a sufficient supply of ATP.

This process of producing ATP is called the “Electron Transport Chain”. The process requires constant removal of excess electrons through the reduction of oxygen. The need for oxygen as an electron acceptor is the sole reason that we respire. In fact, the most immediate purpose of our respiratory and circulatory systems is to deliver oxygen to the tissues for use by mitochondria (and to eliminate carbon dioxide). [3] In this page we will discuss how mitochondria generate ATP, how they are physiologically significant and how they fuse and divide as well as how they interact during the cell division process.


Timeline of Research on Mitochondria
Time Discovery
1890 Description of early mitochondria, named 'bioblasts' by Altman [4]He found that they were ‘elementary organisms’ that carried out vital functions
1898 Mitochondrion name was introduced by Benda and orginates from the greek ‘mitos’ and ‘chondros’ meaning thread and granule respectively; an appearance described during spermatogenesis[5]
1904 Mitochondria first described in plant cells by Meves. [6]He suggested that they were the ‘bearer of genes’ within a cell.
1908 Regaud concluded that mitochondria contain protein and lipid. [7] Along with Meves, he also suggested that mitochondria held genes within the cell.
1912 Battelli and Stern/Kingsbury first identified that mitochondria are used in cell respiration.[8] [9] This was purely based on morphological descriptions rather than chemical ones. This would soon come later.
1925 Keilin first describes cytochromes, which led the way to describing the respiratory chain. [10] [11]
1934 First attempts to isolate the mitochondria was done by Bensley and Hoerr [12] This began the first developments into understanding the chemical componenets of mitochondria. They were able to biochemically analyse mitochondria.
1937 Citric acid cycle formulated by Krebs[13][14], aerobic phosphorylation described by Kalckar [15]
1940-1946 Studies undertaken by Claude to understand the morphological and biochemical studies on isolated mitochondria. [16]
1951-1952 Respiratory control found to be demonstrated by Niemeyer and Lipmann [17] Ten years previous, Lipmann, developed the concept of energy conservation in cellular metabolism[18]
1952-1953 First high resolution electron micrographs of mitochondria were taken by Palade[19] and Sjostrand separately.[20] Palade found that mitochondria is surrounded by a membrane that is folded to form ridges, which he named Cristae. [19] Sjostrand's micrograph demonstrated there was a double lining surrounding, as well as some separating. [20]
1955 Chance and Williams studied oxidative phosphorylation using a dual-wavelength spectrophotometer with an oxygen electrode. This made the fist quantitative study of concentrations of electron transport catalysts, in most cells and tissues[21][22][23][24][25]
1963 -Nass was first to identify what looked like DNA in mitochondria [26][27]
1981 The first complete sequence of mitochondrial DNA in mice was completed by Bibb and his associates. [28]
1996 Mitochondria and apoptosis linked by the BCL-2 family of oncogenes.[29] Proteins of the BCL-2 family have pro-apototic pathways by changing the permeability of the mitochondrial membrane.


Mitochondria Diagram Showing Crista

The Mitochondria is composed of two membranes, known as a double membrane.[30] The outer membrane is a relatively simple phospholipid bilayer. It contains protein structures called porins, which allow the mitochondria to be permeable to some molecules.[31] Permeability is what allows Ions and other substrates to pass through the outer membrane freely.[32]

The inner membrane is a highly complex structure; it is freely permeable only to oxygen, carbon dioxide, and water.[33] The inner membrane includes all of the components of the electron transport chain, the ATP synthetase complex, and transport proteins.[34] It is made up of Cristae, which has a wrinkled appearance being organized into layers. The role of the cristae is to increase the total surface area of the inner membrane.[35] The larger surface created by the cristae allows all the above complexes to occur (electron transport chain, the ATP synthetase complex, and transport proteins)[36]

Combined, the inner and outer membranes create two compartments. The intermembrane space, which is the area between the inner and outer membranes. It has an important role in the primary function of mitochondria, which is oxidative phosphorylation. The other compartment is called the matrix, which is located within the Mitochondria itself. The matrix contains the enzymes that are responsible for the citric acid cycle reactions.[37] The matrix also contains dissolved oxygen, water, carbon dioxide, the recyclable intermediates that serve as energy transports.


Mitochondria are the essential component of a cell responsible for the mobilization of energy and the ability to generate ATP through the oxidative phosphorylation reactions. They also synthesize and the assemble some metabolic substances such as amino acids, fatty acids and some hormones. Recent research from review articles indicate that mitochondria have also emerged as some of the main regulators of aging, oxidative stress and apoptosis. [1] They also contain a small amount of DNA that codes for the protein synthesis made on the organelle's ribosomes.


Beta Oxidation

The first major process that occurs in the mitochondria is B-Oxidation. This is a process where fatty acids and glycerol are used as substrates, 2 at a time are broken down through a series of reactions that oxidise the atoms to produce acetyl-CoA.[38] This substrate is now ready for the the citric acid cycle (TCA-cycle).


Although glycolysis is not performed within the mitochondria, it will be briefly discussed because it is an important step in getting there. The TCA cycle is a continuation of glycolysis and B-Oxidation. In glycolysis each glucose goes through a series of steps and finally concludes as 2 molecules of pyruvate.[39] Now that it is pyruvate it is actively transported through to the inner membrane and into the matrix. The pyruvate molecule in now oxidised and combined with the enzyme coenzyme A to form CO2, acetyl-CoA, and NADH.[40] This is where the TCA cycle begins.

The Citric Acid Cycle

File:TCA cycle.jpg
Citric Acid Cycle

The acetyl-CoA as mentioned above is the first substrate to enter the citric acid cycle (TCA cycle). This substrate then combines with a molecule called oxaloacetate (4 carbon molecule), which releases coenzyme A and forms a molecule called citrate (6 carbon molecule). Citrate is then transformed into isocitrate through oxidative reactions.[41][42] One molecule of CO2 is released as well as Two electrons and one hydrogen (H+) are stripped from Isocitrate, which are transferred to NAD+ to form NADH. From this α-Ketoglutarate (5 carbon molecule) is formed and is also stripped of electrons and H+, which results in another NADH and one molecule of CO2, resulting in succinyl CoA (4 carbon molecule)is converter to oxaloacetate to finish the cycle. The resulting electrons and H+ of the TCA cycle make FADH2 and NADH and one ATP is made.[42]

The Electron Transport Chain

The electron transport chain (ETC) continues from where the TCA cycle finishes. Therefore the resulting FADH2 and NADH enter the ETC, which is processed in the inner membrane of the mitochondria. Here is where majority of ATP is formed. Here the electrons are transferred to protein complexes. This is coupled by pumping protons to outside of the inner membrane, to return in the ATP synthase complex, driving the synthesis of ATP.[43] Let’s talk about the different complexes:

Complex I

NADH Dehydrogenase complex passes electrons from NADH to Coenzyme Q (CoQ).Several iron–sulphur clusters are involved in the electron transport process. The two coenzymes of complex I, flavin mononucleotide (FMN) and CoQ are able to accommodate up to two electrons each in stable conformations and donate one or two electrons to the cytochromes of complex III. It is thought that four protons are pumped per pair of electrons.[44]

Complex II

Succinate–coenzyme Q reductase contains succinate dehydrogenase and three small hydrophobic subunits. It is anchored in the membrane, facing the mitochondrial matrix. It directly passes electrons from succinate, an intermediate of the citric acid cycle, using FAD as a coenzyme, three iron–sulfur clusters and cytochrome b560. It has no proton-pumping activity.[45]

Electron-Transport Chain

Complex III

Coenzyme Q–cytochrome c reductase transfers electrons from reduced CoQ to cytochrome c. It contains two b-cytochromes, one cytochrome c1, and aniron–sulfur cluster. Two protons are pumped per pair of electrons.[46]

Complex IV

Cytochrome c oxidase catalyses the last step of electron transfer: the reduction of oxygen to water. Complex IV translocates four protons per pair of electrons.[47]

ATP Synthase

ATP synthase accepts one proton from the intermembrane space and releases a different proton into the matrix space to create the energy it needs to synthesize ATP. It must do this three times to synthesize one ATP from the substrates ADP and Pi (inorganic phosphate).[36] With the supply of NADH exhausted, the electron transport chain can no longer maintain the proton gradient that powers ATP synthase, and ATP synthesis comes to a stop.[48]


Another function of the mitochondria is heat production, which is created by an uncoupling of mitochondrial respiration. It happens when uncoupling proteins from within the mitochondria are able to transport protons and enhance effects of the heat production function. This process uses wasted energy that the mitochondria creates, which slips through the cracks without being used for the ETC.[49] The process within the mitochondria to create heat assists the body’s main heat production region which is brown adipose tissue. Brown adipose tissue create heat through a process which is mediated by a proton channel called thermogenin. Thermogenin is primarily found in brown adipose tissue and is responsible for non-shivering thermogenesis.[50]

Calcium signalling and storage

Mitochondria’s third main role is that of Calcium signalling. It does this with the help of the endoplasmic reticulum. The mitochondria and the endoplasmic reticulum together modulate the signalling of calcium during cell activation.[51] This is done by concentrating free calcium ions in the cell and storing them to later release them as buffers for the cytosol.[52] It is stored in the mitochondrial matrix until the mitochondria membrane potential has been reached, which to get there travels via a uniporter which is located within the inner membrane of the mitochondria.[51][53] When the mitochondria membrane potential has been reached the calcium spikes and is then released to further help coordinate processes in nerve cells, such as neurotransmitter release and the release of hormones in endocrine cells.[54]


Mitochondria also function in the apoptotic process of cells. Apoptosis is the process in which cells die.[52] They do this by creating reactive oxygen species which are the key elements in the apoptotic pathway.[55]this then leads to the function of Mitochondria to control the intrinsic apoptotic pathway and therefore influence the programmed death of cells.[52]

During Cell Division

As most cells, if not all cells, need mitochondria to survive, in cell division mitochondria are equally segregated out between both mother cell and daughter cell. A daughter cell that does not receive any mitochondria will shortly die. The actin cytoskeleton has a large influence on how the mitochondria are divided between both mother and daughter cell as it influences motility as well as retention of mitochondria when the cell divides.[56] Much research has been undertaken in budding yeast to demonstrate the roles the actin skeleton plays. In this budding yeast, mitochondria are tubular structures that separate and move towards one of the ends of the cell, which would have formed 'tips', a bud tip and a mother cell tip. [57] If the mitochondrion is moved to the bud tip it is call 'anterograde' and if towards the mother cell tip, 'retrograde'.[58] [59] After this movement they are held in place at the retention zone until the end of the cell division cycle. [56]


Actin cables are usually found in both movements, and both retrograde and anterograde have similar mechanisms but are not identical. The f actin budles extend from mother cells to daughter cell or bud tip and consist of parallel bundles with their plus end toward the contact point with the plasma membrane. As the length or density of the fibers vary they structure is very much the same in most organisms. New material of the actin bundles is assembled at the contact point and thus, pushes the actin, as well as the mitochondria joined to it at a fixed point, in a retrograde direction. Formins and tropomysoin proteins stimulate and stabilize the newly formed actin as it pushes forwards. [59] [60]


Studies suggest that anterograde movement of the mitochondria is similar to retrograde but is generated by the Arp2/3 complex which forms actin comet tails that bundle into cables and result in linear cargo movement. [1]

Proteins formed from the genes MMM1, MDM10 and MDM12 have major roles in the membrane protein complex that covers both inner and outer membrane and is essential for normal mitochondrial morphology and membranes and is an essential component that links the membrane with the actin cytoskeleton for movement. [61] While both MDM10 and MDM12 proteins are essential for the outer membranes, the MMM1 protein is found at the contact sites where both inner and outer membranes are close. [62] But they all work together to prevent abnormalities that would result in organelle death and cell death. As these proteins are very closely linked with the actin cytoskeleton, an abnormality within these spots could cause a lack of movement along the actin cytoskeleton, preventing the transfer from mother to daughter cell. [61]

Though mitochondria can be moved, after they have reached the poles, they are retained by certain mechanisms that prevent further mitochondrial transfers. Myo2p (a V type myosin) and Ypt11p (Myo2p binding protein)have been implicated as main players in the retention of mitochondria at the poles. [63] During mitosis in budding yeast, the mitochondria form a network of interconnected tubules in line with that of the actin filaments and cables at the cell cortex [64] [65] These tubules are determined by the fusion and fission events that occur.[65]

Mitochondrial Fission and Fusion

Mitochondria are quite dynamic organelles, and tightly regulated by the processes of fission and fusion which enable the organelle to change in morphology, activity and distribution outside that of the regular cell replication and division process.[66] [2] The molecular machinery has been studied and found that not only do these regulate mitochondria, but if there is a decreased amount of these processes, or complete lack of, then it can impact dramatically on normal development, cell function, and human disease. [67] [68] For instance, a lack of fusion can lead to developmental issues and degenerative diseases in mice and humans respectively.[69]

The first identification that began the process of unravelling the mitochondrial dynamics was the finding of Fzo, a mitofusin gene in Drosophila[70]. While most fusion and fission machinery is usually present in mammals, [2]there are usually yeast counterparts too. An example is the homolog Fzo1, which is said to function similarly to that of Fzo but is found in yeast. [71] Screening for gene suppressors in mutations in fusion has led to many findings about the genetics involved in mitochondrial fission [72]


Time Course of the Fusion of Mitochondria

As stated before Fzo, or Drosphila Fuzzy Onions [73] is a mitofusion gene found in drosophila, Fzo1 is found in yeast, their mammalian counterpart in mitofusion genes consists of two genes, Mfn1 and Mfn2. Other genes used in the fusion pathway in yeast is Mgm1, Ugo1 and in mammals OPA1.

Mfn1 and Mfn2

Mfn1 and Mfn2 are two mammalian mitofusion homologues and because they are so closely related, they both play very similar roles, and are essential for normal regulation of mitochondrial fusion. They also replace each other, if one is under expressing or not expressing at normal amounts the other will over-express and functionally replace each other. [74] But cells lacking in both mitofusion genes have a decreased rate and amount of mitochondrial fusion. [75][74] Both of these mitofusion genes were discovered by targeted mutations in mice. [75] As stated above, Fzo is the Drosophila counter part and Fzo1 is the yeast counter part to that of the human homologues Mfn1 and Mfn2


OPA1, the mammalian equivalent to the yeast Mgm1, was first associated and identified as a mutated gene that caused visual loss [76] in autosomeal dominant optic atrophy. Both genes are located in the mitochondrial intermembrane space and have associations with the inner membrane. [77] OPA1 gene codes for many proteins and is essential for fusion, just like the mitofusions. Overepression of OPA1 leads to elongation or even fragmentation of the mitochondria.[74] [77] OPA1 RNAi leads to problems with the cristae structure [77]and lack of OPA1 leads to fragmentation of the mitochondria during the fusion process. [74] [77]


The mitochondrial fission pathway has a combination of many genes that can affect the overall outcome of the mitochondria function. The mammalian proteins that code for fission are Drp1, and hFis1 and suggested molecules such as Endophilin B1 and MTP18. And in yeast Dnm1, Mdv1, Fis2, Gag3, Net2, and Fis1, and Mdv2.

Drp1 and Dnm1

Dnm1p (for yeast) or Drp1 (for mammals), a dynamin-related GTPase is the key factor for mitochondrial division. [78] In order for mitochondrial division to take place, Dnm1p/Drp1 is recruited to the outer membrane of the organelle surface from the cytosol, where they are present abundantly. However, it is essential for other proteins to be present on the organelle surface for the recruitment of Dnm1p/Drp1. [79]


Fis/Fis1 Another major protein used in the fission pathway is Fis/Fis1,[72] it is an outer membrane protein which is placed in uniform locations on the mitochondria and regulates the fragmentation process what is used in fission. This protein also helps target the Drp1 to the surface of the mitochondria[72] Overexpression of Fis1 leads to complete fragmentation[80] while an underexpression causes an elongation of the mitochondria.[81]

Other Proteins

Mdv1 results in the colonisation of Dnm1,[82];[83])as well as an interaction between the two.[84]

Endophilin B1 forms crescent shaped dimmers when it interacts with the lipid membranes [85] When there is a lack of B1, the morphology of mitochondria changes causing abnormalities which change the overall outcome of fission. [86] Most cells with a lack of B1 have strange interconnections and contain long thin tubules that will stain for outer membrane markers but not matrix markers. This may suggest that B1 has a role in the control of the outer membrane.

MPT18 is shown to lead to mitochondrial fragmentation when it is over expressed which shows it may have a role in mitochondrial fission, but it yet to be proven.[87]

Fission In Yeast Through two functionally overlapping WD-40 domain-containing adaptor proteins, Mdv1p, and Caf4p, the integral outer membrane protein Fis1p provides an anchoring site for Dnm1p in yeast. [79] Mdv1p acts as a structural nucleation factor promoting the anchorage of Dnm1p on the membranes; this could possibly be a key regulatory step for mitochondrial division. [88]

In addition to the Fis1p-Mdv1p/Caf4p dynamics, a separate binding site for Dnm1p is also provided by a cortical protein, Num1p for mitochondrial division. [89] Num1p together with Mdm36p, another outer membrane protein, enhances the stable association of Dnm1p and Num1p. [90]

Fission In Mammals In mammals, Drp1 is anchored to the mitochondria membrane surface via direct interaction with mitochondria fission factor (Mff1), a recently identified integral outer membrane protein. [91] A variety of post-translational modifications, including phosphorylation, sumoylation and ubiquitination regulates mitochondrial recruitment of Drp1 from the cytosol. [92]

Physiological Significance of Mitochondrial Division

The involvement of mitochondrial division in cellular functions such as energy metabolism, apoptosis, calcium signalling, organelle shaping and distribution have been evident from the numerous studies conducted using in vitro cell culture systems and simple eukaryotic models.

However, due to a lack of animal models, the physiological function of mitochondrial division in mammals were unknown till the generation and characterisation of complete and brain specific Drp1 knockout mice in recent studies.[93][94] Drp1 have been shown to be essential for embryonic development as the embryos of complete knockouts were unable to survive pass the placenta development stage. Highly connected mitochondrial tubules and greatly decreased mitochondrial division rates were showed in embryonic fibroblasts derived from the knockout mice. Analysis of Drp1-null knockout mice embryonic fibroblasts also suggest that mitochondrial fusion might be regulated by mitochondrial division. These studies emphasise the importance of mitochondrial division in the physiological function of mammals.

Some evidence that mitochondrial division regulates mitochondrial fusion has also surfaced from the studies.[93] [94] A balance between mitochondrial division and mitochondrial fusion is crucial for the maintenance of mitochondria. Through the studies using Drp-1 null knockout mouse embryonic fibroblasts and Drp1-specific siRNA,[93][94][95] it is evident that steady state levels of Mfn1 and Mfn2 decreases due to a loss of Drp1.

The loss of Drp1 also prevents normal cerebellar development. [93] Drp1 is highly expressed in Purkinje cells, deleting Drp1 in the developing cerebellum causes a change in the shape of mitochondria from short tubules to large spheres in the Purkinje neurons.[93] Therefore, the shape of mitochondria might be regulated by mitochondrial division mechanisms too.

Mitochondrial division in Human Diseases

The importance of the physiological functions of mitochondrial division dynamics has been further emphasised due to its associations with several human diseases, especially diseases affection neurons.[96][97][98]

Studies have shown that neurodegenerative diseases such as Alzheimer’s disease and Huntington’s disease are associated with mitochondrial fusion and division. [99][100][79][101] Drp1 mutations underlie neurodevelopment abnormalities; similarly mutations in Mfn2 and Opa1 have also been identified as the underlying factors resulting in neurological disorders including Charcot-Marie-Tooth disease type 2A and autosomal dominant optic atrophy. [102][103][104][105]

Neurodegeneration Mechanism

Neurodegeneration Mechanism Model

In a recent study, [93] it has been revealed that a loss of Drp 1 causes a change in the shape of mitochondria from short tubules to large spheres in the Purkinje cells due to blockage of mitochondrial division. In the event of mitochondrial division blockage, imbalanced, excess fusion occurs causing the elongation of mitochondria. Oxidative damage is accumulated in the elongated tubule form of mitochondria, leading to the swelling of the mitochondria cell and impairment of the electron transport chain. Respiratory competence is decreased due the enlargement of mitochondria. The decline in respiration eventually results in neuronal death, causing neurodegeneration and neurodevelopment abnormalities.

Alzheimer's Disease

In a recent study of Alzheimer’s disease, [106] it has been suggested that changes in mitochondrial dynamics may be involved in the pathogenesis of this common age-related disease as the earliest known event in Alzheimer’s disease is mitochondrial dysfunction.

Altered distribution of mitochondria away from axons in the pyramidal neurons of the Alzheimer’s disease brain observed. Analysis from the study[106] revealed that levels of Drp1, OPA1, Mfn1 and Mfn2 decreased significantly whereas Fis1 levels were increased significantly in the onset of Alzheimer’s disease. The changes in the levels of these mitochondrial fusion and fission protein accounts for the altered distribution of mitochondria in neuronal cells. Mitochondrial fragmentation and a reduction in mitochondrial density in neuronal processes also occur due to oligomeric amyloid-beta-derived diffusible ligands (ADDLs).

Another study[100] provided evidence that S-nitrosylation of Drp1 was increased in Alzheimer’s patients, leading to activation of Drp1 GTPase activity, excess mitochondrial division, and ultimately neural injury.

Huntington's Disease

Huntington's disease, an autosomal dominant and fatal neurological disease has also been associated mitochondrial dysfunction.

Increased Drp1 levels were observed in the brains of patients suffering from Huntington’s disease.[107] Thus, it is evident that mitochondrial division has been implicated in the onset of the disease. This is further supported by another study in which it has been observed that excess mitochondrial fission over mitochondrial fusion leads to the fragmentation of mitochondria, contributing to cell death in cellular models of Huntington’s disease.[108]

It has also been suggested that activation of Drp1 dependent mitochondrial division by the processes of phosphorylation and de-phosphorylation may be involved in hypersensitivity to apoptosis in Huntington’s cellular models.[109]

Charcot-Marie-Tooth disease type 2A

Charcot-Marie-Tooth disease type 2A is a neurological disorder which arises due to heterozygous mutations in the mitochondrial fusion gene MFN2, the gene encoding mitofusin 2 (Mfn2).[110] This disease is a dominantly inherited peripheral neuropathy characterised by axonal degeneration of motor and sensory neurons. [111][112][113]

Due to low levels of Mfn1, peripheral nerves are more sensitive to the presence of mutant Mfn2 proteins.[114][115] A population of energetically heterogeneous mitochondria may be generated in cells that are present in an environment with minimal levels of Mfn1.[74][116] This is due to the formation of dominantly non-functional Mfn2-Mfn2mutant fusion complexes which results in the reduced frequency of efficient mitochondrial fusion.[114] The energetically heterogeneous mitochondria are preferentially transported from synapses back to the cell bodies as axonal transport of mitochondria is dependent on mitochondrial function.[117] Thus, there is a lack of mitochondria at the nerve terminal to provide the amount of energy required for synaptic function.[118]

Alternatively, mitochondrial aggregation which may arise from mutant fusion complexes prolonging the fusion of adjacent mitochondria causes axonal transport defects, which further aggravates the mitochondria shortage situation.[119][114]

Progressive degeneration of peripheral nerve axons and terminals resulting from the depletion of mitochondria gives rise to the clinical symptoms of Charcot-Marie-Tooth type 2A.

Autosomal dominant optic atrophy

The major form of autosomal dominant optic atrophy or Kjer’s disease arises due to mutations in Opa1. Patients suffering from this disease experience progressive loss of visual acuity from the degeneration of retinal ganglion cells.[120]

Although the mechanism as to how Opa1 mutations result in the degeneration of retinal ganglion cell is still unknown, clumped mitochondria have been observed in monocytes of patients suffering from autosomal dominant optic atropy.[103] The formation of mitochondrial aggregates is caused by the knockdown of Opa1 in the retina.[121]

Decreased levels of oxidative phosphorylation in skeletal muscle as well as reduced copies of mitochondrial DNA have been indicated from clinical analysis of autosomal dominant optic atrophy patients too. [122][123] Severe reduction of mitochondrial membrane potential and respiration of Opa1 deficient cells have been suggested as the underlying causes of such defects.[74] Apoptosis and severe cristae defects within mitochondrial cell also occur from the loss of Opa1.[124][125]

Hence, Opa1 mutations which affect mitochondrial fusion dynamics have been suggested as the cause of retinal ganglion cell degeneration.


Anterograde Movement of the Mitochondria toward the daughter cell tip. Also known as orthograde in some other instances.

ATP Adenosine triphosphate- is the universal creator of energy within cells.

Apoptosis This is the process of cell death within cells.

Crista Or Cristae (plural) are the internal compartments formed by the folding of the inner membrane within the mitochondrion.

Coenzyme A nonproteinaceous organic substance that combines with a specific protein.

Cytoskeleton this structure helps to maintain cell shape.

Energy yielding This is the process of creating energy used by the ATP.

Fission Division of the Mitochondria separate to that of the normal cell cycles.

Fusion When two or more Mitochondria fuse together. Can sometimes form a mesh work inside the cell.

Homologues A similar but not identical structure or function. In the instance used here, a similar but not identical codon for proteins.

Mitochondrion A singular Mitochondria.

Organelle This is a specialized subunit within a cell that has a specific function.

Retrograde Movement of the Mitochondria toward the mother cell tip.

Ribosomes (from ribonucleic acid and the Greek soma, meaning "body") Ribosomes are a molecular structure found within all living cells.

Substrate This is a surface where an organism grows or is attached.


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2013 Projects: Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6 | Group 7

Dr Mark Hill 2013, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G