The electrons from NADH pass first to the flavin a biomolecule produced from riboflavin then it will go through 7 iron-sulfur centers to the ubiquinone or coenzyme Q . Complex II is the succinate dehydrogenase.
Mitochondrial Dna Cytochrome C Oxidase Biology Essay
Here, additional electrons are sent into the quinone pool Q . Complex III is the cytochrome b-c1 complex. It contains 22 protein chains with 6 heme groups in cytochromes and an addition of 2 iron-sulfur centers.
Its duty is to pass electrons to cytochrome c . Complex IV is the cytochrome oxidase complex. In this particular complex, 26 protein chains including 4 cytochromes each attached with 2 copper atoms are contained. Complex IV has the duty to receive electrons from cytochrome c one at a time. It will then pass them four at a time to oxygen to produce water. The copper atoms present her bind to peptide chains and transfer electrons one at a time. Copper is incorporated into heme a3 where electrons gather at the end of the ETC .
When electrons pass through flavin, protons are drawn along. The electrons then traverse a series of iron-sulfur boxes.
Electrons pass along parallel pathways through complex III. The heme group of cytochrome c is the one responsible to transport electron pairs to Complex IV. After transported to Complex IV, the spent electrons accumulate at heme a3.
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Meanwhile, molecules of oxygen O2 diffuse into the cell. The oxygen molecules are then captured by the iron copper core at heme a3. Oxygen is very attracted to electrons, but adding fewer than four electrons at a time makes oxygen unstable.
So, heme a3 holds the apart until four electrons accumulate. When these four once high-energy electrons have accumulated at heme a3, they are all fed at once to oxygen. Therefore, by taking these, the result is water H2O . The protons are trapped in the intermembrane space between the inner membrane and outer membrane of the mitochondria by their attraction to high energy electrons. After water is produced previous paragraph , the number of hydrogen ions trapped in the intermembrane space are approximately ten times higher than inside the mitochondrial matrix.
When this occurs, the ATP Synthase will make its move . The ATP Synthase has 2 subunits. The FO subunit lies within the inner membrane while the F1 subunit is above the membrane — inside the mitochondrial matrix. The FO subunit is more like rotor. It works by spinning, thus moving up protons from the intermembrane space towards the mitochondrial matrix. This ability is done by the energy in the form of protons moving down an electrochemical gradient.
This contraption of such an enzyme is powered by the pH eagerness of protons to return to the mitochondrial matrix, and provides a channel for them to do so. There will be a time where this mechanism is inhibited to stop transportation of protons down the electrochemical gradient when is not necessary. If this mechanism is inhibited, the reaction of ATP production will not take place . A scheme of ATP Synthase . FO as seen above lies within the phospholipid bilayer of the mitochondrial inner membrane and forms some kind of a rotor mechanism.
The F1 subunit lies above or below the FO subunit in the mitochondrial matrix. The scheme above also describes the ATP synthase in a fully active mode and an inhibited or inactive mode.
The structure of mitochondria
Apart from being the major power plants of cells, mitochondria also have several other functions and roles within the cell. Mitochondria also possess a crucial role in apoptosis and calcium ions storage. Apoptosis is defined as programmed cell death. Apoptosis serves as major defense mechanism in the regulation of cell numbers to prevent harmful and unwanted cells to grow. Scientists back then studied the disappearance of the tails and gills of juvenile frogs growing to adulthood.
The advantages of apoptosis include membrane blebbing, cell shrinkage, chromatine condensation, DNA cleavage, cell fragmentation, and also the phagocytosis of a cell . Apoptosis can be divided into three major phases; the activation phase, the execution phase, and the destruction phase. The first phase is the activation phase.
During this phase, multiple signaling pathways lead from the various death-triggering signals to the central control of the cell death machinery and then activate it. The next phase is the execution phase. Here, the activated machinery acts on multiple cell targets. Then, the final phase is the destruction phase. During this final stage, the targeted dead or dying cell is then broken down and degraded by degrading enzymes and engulfed by phagositosic cells . One of the most crucial ced in apoptosis are ced-3, ced-4, and ced Hence, ced-9 protects the cells that should survive whenever there is a sudden accidental activation of the cell death mechanism .
Calcium ions concentration in the cell is crucial. This means that mitochondria harness a substantial role in calcium ions homeostasis within a cell [27, 28]. Recent studies show that the endoplasmic reticulum ER is the most significant calcium storage site and there is also a significant relationship between the ER and mitochondria concerning calcium uptakes . Calcium ions are taken up by the mitochondrial matrix by a calcium uniporter integral protein on the inner mitochondrial membrane .
This flow is mainly initiated by the mitochondrial membrane potential. The accumulation of calcium ions within the mitochondria regulates mitochondrial metabolism and has the ability to cause a transient depolarization of mitochondrial membrane potential. Like any organelle, a dysfunction of the mitochondria will lead into a mitochondrial disorder or disease. As a vital organelle in the metabolic system, even a slight disorder in the function of the mitochondria can be harmful to the cell. Apart from mutations, mitochondrial diseases can also be attained by inheritance.
The cells that are the most affected when a mitochondrial disorder occurred are the muscle and brain cells. These cells require a lot of energy to induce their activity . The human mtDNA is approximately 16 kbp long and encode 37 genes. Before the fertilization of an ovum egg cell by a sperm cell, these two parental cells each have mitochondria.
Regulation of Succinate Dehydrogenase Activity by SIRT3 in Mammalian Mitochondria | Biochemistry
In a sperm cell, the mitochondria are located at the base of the tail or flagellum. Sperm cells need to obtain lots of energy because it swims independently and competes with millions of other sperm cells towards an ovum, therefore, require a lot of energy for their movement. Men semen contains sucrose sugar to supply the sperm cells food to obtain enough energy to do its journey down the oviduct. However, during fertilization, the sperm cell will lose its tail or will discard its tail while it drills and penetrates into the wall of an ovum. This means that the mitochondria containing tail did not penetrate the ovum, resulting in no traces of mitochondria from the sperm cell father.
Therefore, a human mitochondrial disease transferred paternally is theoretically impossible . In the following are some examples of mitochondrial diseases that are present among human beings. MELAS Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke Syndrome is a chronic progressive neurodegenerative disorder. The nervous system seems to have broken down and degenerated. Early symptoms of MELAS include muscle weakness, joint pain, recurrent headaches, appetite loss, frequent vomiting, and seizures.
Further symptoms include stroke-like episodes along with vision abnormalities and severe headaches. Extremely ill patients have been known to lose sight, moving problems, and decreasing intellectual . It is an extremely rare mitochondrial disease. Patients suffering from this disease will experience muscle weakness or cardiac problems, epilepsy, and dementia.
MNGIE is a multi-system disorder with symptoms such as; malabsorption of the gastro-intestinal tract, diarrhea, constipation, gastroparesis delayed gastric emptying , vomiting, weight loss, peripheral neuropathy, and retinal degeneration . Mitochondrial research has been a very interesting board of interest over the past few decades. It is always very interesting to follow the development of mitochondrial research because there still remain many unsolved mysteries, mysteries that have yet to be even discovered.
Nowadays, there are many companies and societies worldwide that dedicate themselves to mitochondrial research exclusively.
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