Special structures - mitochondria - play an important role in the life of each cell. The structure of mitochondria allows the organelle to operate in a semi-autonomous mode.
general characteristics
Mitochondria were discovered in 1850. However, it became possible to understand the structure and functional purpose of mitochondria only in 1948.
Due to their rather large size, the organelles are clearly visible in a light microscope. The maximum length is 10 microns, the diameter does not exceed 1 micron.
Mitochondria are present in all eukaryotic cells. These are double-membrane organelles, usually bean-shaped. Mitochondria are also found in spherical, filamentous, and spiral shapes.
The number of mitochondria can vary significantly. For example, there are about a thousand of them in liver cells, and 300 thousand in oocytes. Plant cells contain fewer mitochondria than animal cells.
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Rice. 1. The location of mitochondria in the cell.
Mitochondria are plastic. They change shape and move to the active centers of the cell. Typically, there are more mitochondria in those cells and parts of the cytoplasm where the need for ATP is higher.
Structure
Each mitochondrion is separated from the cytoplasm by two membranes. The outer membrane is smooth. The structure of the inner membrane is more complex. It forms numerous folds - cristae, which increase the functional surface. Between the two membranes there is a space of 10-20 nm filled with enzymes. Inside the organelle there is a matrix - a gel-like substance.
Rice. 2. Internal structure of mitochondria.
The table “Structure and functions of mitochondria” describes in detail the components of the organelle.
|
Compound |
Description |
Functions |
|
Outer membrane |
Consists of lipids. Contains a large amount of porin protein, which forms hydrophilic tubules. The entire outer membrane is permeated with pores through which molecules of substances enter the mitochondria. Also contains enzymes involved in lipid synthesis |
Protects the organelle, promotes the transport of substances |
|
They are located perpendicular to the mitochondrial axis. They may look like plates or tubes. The number of cristae varies depending on the cell type. There are three times more of them in heart cells than in liver cells. Contains phospholipids and proteins of three types: Catalyzing - participate in oxidative processes; Enzymatic - participate in the formation of ATP; Transport - transport molecules from the matrix out and back |
Carries out the second stage of breathing using the respiratory chain. Hydrogen oxidation occurs, producing 36 molecules of ATP and water |
|
|
Consists of a mixture of enzymes, fatty acids, proteins, RNA, mitochondrial ribosomes. This is where mitochondria's own DNA is located. |
Carries out the first stage of respiration - the Krebs cycle, as a result of which 2 ATP molecules are formed |
The main function of mitochondria is the generation of cell energy in the form of ATP molecules due to the reaction of oxidative phosphorylation - cellular respiration.
In addition to mitochondria, plant cells contain additional semi-autonomous organelles - plastids.
Depending on the functional purpose, three types of plastids are distinguished:
- chromoplasts - accumulate and store pigments (carotenes) of different shades that give color to plant flowers;
- leucoplasts - store nutrients, such as starch, in the form of grains and granules;
- chloroplasts - the most important organelles that contain the green pigment (chlorophyll), which gives plants color, and carry out photosynthesis.
Rice. 3. Plastids.
What have we learned?
We examined the structural features of mitochondria - double-membrane organelles that carry out cellular respiration. The outer membrane consists of proteins and lipids and transports substances. The inner membrane forms folds - cristae, on which hydrogen oxidation occurs. The cristae are surrounded by a matrix - a gel-like substance in which some of the reactions of cellular respiration take place. The matrix contains mitochondrial DNA and RNA.
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Mitochondria are the organelles that supply energy to metabolic processes in the cell. Their sizes vary from 0.5 to 5-7 microns, the number in a cell ranges from 50 to 1000 or more. In the hyaloplasm, mitochondria are usually distributed diffusely, but in specialized cells they are concentrated in those areas where there is the greatest need for energy. For example, in muscle cells and symplasts, large numbers of mitochondria are concentrated along the working elements - contractile fibrils. In cells whose functions involve particularly high energy consumption, mitochondria form multiple contacts, uniting into a network or clusters (cardiomyocytes and symplasts of skeletal muscle tissue). In the cell, mitochondria perform the function of respiration. Cellular respiration is a sequence of reactions by which a cell uses the energy of bonds of organic molecules to synthesize high-energy compounds such as ATP. ATP molecules formed inside the mitochondrion are transferred outside, exchanging for ADP molecules located outside the mitochondrion. In a living cell, mitochondria can move using cytoskeletal elements. At the ultramicroscopic level, the mitochondrial wall consists of two membranes - outer and inner. The outer membrane has a relatively smooth surface, the inner one forms folds or cristae directed towards the center. Between the outer and inner membranes a narrow (about 15 nm) space appears, which is called the outer chamber of the mitochondrion; the inner membrane defines the inner chamber. The contents of the outer and inner chambers of the mitochondria are different, and just like the membranes themselves, they differ significantly not only in surface relief, but also in a number of biochemical and functional characteristics. The outer membrane is similar in chemical composition and properties to other intracellular membranes and the plasmalemma.
It is characterized by high permeability due to the presence of hydrophilic protein channels. This membrane contains receptor complexes that recognize and bind substances entering the mitochondria. The enzyme spectrum of the outer membrane is not rich: these are enzymes for the metabolism of fatty acids, phospholipids, lipids, etc. The main function of the outer membrane of the mitochondria is to separate the organelle from the hyaloplasm and transport the substrates necessary for cellular respiration. The inner membrane of mitochondria in most tissue cells of various organs forms plate-shaped cristae (lamellar cristae), which significantly increases the surface area of the inner membrane. In the latter, 20-25% of all protein molecules are enzymes of the respiratory chain and oxidative phosphorylation. In the endocrine cells of the adrenal glands and gonads, mitochondria are involved in the synthesis of steroid hormones. In these cells, mitochondria have cristae in the form of tubes (tubules), orderedly located in a certain direction. Therefore, the mitochondrial cristae in the steroid-producing cells of these organs are called tubular. The mitochondrial matrix, or the contents of the inner chamber, is a gel-like structure containing about 50% proteins. Osmiophilic bodies, described by electron microscopy, are calcium reserves. The matrix contains enzymes of the citric acid cycle, which catalyze the oxidation of fatty acids, the synthesis of ribosomes, and enzymes involved in the synthesis of RNA and DNA. The total number of enzymes exceeds 40. In addition to enzymes, the mitochondrial matrix contains mitochondrial DNA (mitDNA) and mitochondrial ribosomes. The mitDNA molecule is ring-shaped. The possibilities of intramitochondrial protein synthesis are limited - transport proteins of mitochondrial membranes and some enzymatic proteins involved in ADP phosphorylation are synthesized here. All other mitochondrial proteins are encoded by nuclear DNA, and their synthesis occurs in the hyaloplasm, and they are subsequently transported into the mitochondrion. The life cycle of mitochondria in a cell is short, so nature has endowed them with a dual reproduction system - in addition to the division of the mother mitochondria, the formation of several daughter organelles through budding is possible.
Mitochondria are organelles the size of bacteria (about 1 x 2 microns). They are found in large numbers in almost all eukaryotic cells. Typically, a cell contains about 2000 mitochondria, the total volume of which is up to 25% of the total cell volume. The mitochondrion is bounded by two membranes - a smooth outer one and a folded inner one, which has a very large surface. The folds of the inner membrane penetrate deeply into the mitochondrial matrix, forming transverse septa - cristae. The space between the outer and inner membranes is usually called the intermembrane space. The mitochondrion is the cells' only source of energy. Located in the cytoplasm of every cell, mitochondria are comparable to “batteries” that produce, store and distribute the energy necessary for the cell.
Human cells contain on average 1,500 mitochondria. They are especially numerous in cells with intense metabolism (for example, in muscle or liver).
Mitochondria are mobile and move in the cytoplasm depending on the needs of the cell. Due to the presence of their own DNA, they multiply and self-destruct regardless of cell division.
Cells cannot function without mitochondria; life is not possible without them.
Different types of cells differ from each other both in the number and shape of mitochondria and in the number of cristae. Mitochondria in tissues with active oxidative processes, for example in the heart muscle, have especially many cristae. Variations in mitochondrial shape, which depend on their functional state, can also be observed in tissues of the same type. Mitochondria are variable and plastic organelles.
Mitochondrial membranes contain integral membrane proteins. The outer membrane contains porins, which form pores and make the membrane permeable to substances with a molecular weight of up to 10 kDa. The inner membrane of mitochondria is impermeable to most molecules; the exceptions are O2, CO2, H20. The inner membrane of mitochondria is characterized by an unusually high protein content (75%). These include transport carrier proteins), enzymes, components of the respiratory chain and ATP synthase. In addition, it contains an unusual phospholipid, cardiolipin. The matrix is also enriched with proteins, especially enzymes of the citrate cycle. Mitochondria are the “power station” of the cell, since due to the oxidative degradation of nutrients they synthesize most of the ATP (ATP) needed by the cell. A mitochondrion consists of an outer membrane, which is its shell, and an inner membrane, the site of energy transformations. The inner membrane forms numerous folds that promote intense energy conversion activity.
Specific DNA: The most remarkable feature of mitochondria is that they have their own DNA: mitochondrial DNA. Regardless of nuclear DNA, each mitochondrion has its own genetic apparatus. As its name suggests, mitochondrial DNA (mtDNA) is found inside mitochondria, small structures located in the cytoplasm of the cell, unlike nuclear DNA, which is packaged into chromosomes inside the nucleus . Mitochondria are present in most eukaryotes and have a single origin, it is believed, from one ancient bacterium, which at the dawn of evolution was once absorbed by the cell and turned into its component part, which was “entrusted” with very important functions. Mitochondria are often called the “energy stations” of cells for the reason that they produce adenosine triphosphoric acid (ATP), the chemical energy of which the cell can use almost everywhere, just as a person uses the energy of fuel or electricity for his own purposes. And in the same way, the production of fuel and electricity requires a considerable amount of human labor and the coordinated work of a large number of specialists; the production of ATP inside the mitochondria (or “cellular respiration”, as it is called) uses a huge amount of cellular resources, including “fuel” in the form of oxygen and some organic substances, and of course involves the participation of hundreds of proteins in this process, each of which performs its own specific functions.
To call this process simply “complex” will probably not be enough, because it is directly or indirectly connected with most other metabolic processes in the cell, due to the fact that evolution has endowed each “cog” of this mechanism with many additional functions. The basic principle is to create conditions when inside the mitochondrial membrane it becomes possible to add another phosphate to the ADP molecule, which is “energetically” unrealistic under normal conditions. Conversely, the subsequent use of ATP is the ability to break this bond, releasing energy that the cell can use for its many purposes. The structure of the mitochondrial membrane is very complex; it includes a large number of proteins of various types, which are combined into complexes, or, as they say, “molecular machines” that perform strictly defined functions. Biochemical processes occurring inside the mitochondrial membrane (tricarboxylic cycle, etc.) take in glucose as an input and produce carbon dioxide and NADH molecules as output products, which are capable of splitting off a hydrogen atom, transferring it to membrane proteins. In this case, a proton is transferred to the outside of the membrane, and the electron is ultimately taken by an oxygen molecule on the inside. When the potential difference reaches a certain value, protons begin to move into the cell through special protein complexes, and combining with oxygen molecules (which have already received an electron), they form water, and the energy of moving protons is used in the formation of ATP. Thus, the input of the whole process is carbohydrates (glucose) and oxygen, and the output is carbon dioxide, water and a supply of “cellular fuel” - ATP, which can be transported to other parts of the cell.
As mentioned above, the mitochondrion inherited all these functions from its ancestor - an aerobic bacterium. Since a bacterium is an independent single-celled organism, inside it there is a DNA molecule that contains sequences that determine the structure of all the proteins of a given organism, that is, directly or indirectly, all the functions it performs. When a protomitochondrial bacterium and an ancient eukaryotic cell (also a bacterium in origin) merged, the new organism received two different DNA molecules - nuclear and mitochondrial, which, apparently, initially encoded two completely independent life cycles. However, inside a new single cell such an abundance of metabolic processes turned out to be unnecessary, since they largely duplicated each other. The gradual mutual adaptation of the two systems led to the replacement of most mitochondrial proteins with the eukaryotic cell's own proteins, capable of performing similar functions. As a result, sections of the mitochondrial DNA code that previously performed certain functions became non-coding and were lost over time, leading to the reduction of the molecule. Due to the fact that some forms of life, such as fungi, have very long (and fully functioning!) chains of mitochondrial DNA, we can judge the history of the simplification of this molecule quite reliably by observing how, over the course of millions of years, certain or different branches of the Tree of Life were lost. its other functions. Modern chordates, including mammals, have mtDNA ranging from 15,000 to 20,000 nucleotides in length, the remaining genes of which are located very closely together. Only a little more than 10 proteins and only two types of structural RNA are encoded in the mitochondrion itself; everything else that is required for cellular respiration (more than 500 proteins) is provided by the nucleus. Perhaps the only subsystem that has been preserved entirely is transfer RNA, the genes of which still lie in mitochondrial DNA. Transfer RNAs, each of which includes a three-nucleotide sequence, serve for the synthesis of proteins, with one side “reading” the three-letter codon specifying the future protein, and with the other adding a strictly defined amino acid; the correspondence between trinucleotide sequences and amino acids is called the “translation table” or “genetic code”. Mitochondrial transfer RNAs are involved only in the synthesis of mitochondrial proteins and cannot be used by the nucleus because small differences have accumulated between the nuclear and mitochondrial codes over millions of years of evolution.
Let us also mention that the structure of mitochondrial DNA itself has been significantly simplified, since many components of the DNA transcription (reading) process have been lost, as a result of which the need for special structuring of the mitochondrial code has disappeared. Polymerase proteins that perform transcription (reading) and replication (doubling) of mitochondrial DNA are encoded not in it itself, but in the nucleus.
The main and immediate cause of the diversity of life forms is mutations of the DNA code, that is, the replacement of one nucleotide with another, the insertion of nucleotides and their deletion. Like nuclear DNA mutations, mtDNA mutations mainly occur during the multiplication of the molecule - replication. However, mitochondrial division cycles are independent of cell division, and therefore mutations in mtDNA can occur independently of cell division. In particular, there may be some minor differences between mtDNA located in different mitochondria within the same cell, as well as between mitochondria in different cells and tissues of the same organism. This phenomenon is called heteroplasmy. There is no exact analogue of heteroplasmy in nuclear DNA: an organism develops from a single cell containing a single nucleus, where the entire genome is represented by a single copy. Later, during the life of an individual, various tissues can accumulate the so-called. somatic mutations, but all copies of the genome ultimately come from one. The situation with the mitochondrial genome is somewhat different: a mature egg contains hundreds of thousands of mitochondria, which, as they divide, can quickly accumulate small differences, with the entire set of variants being inherited by a new organism after fertilization. Thus, if discrepancies between nuclear DNA variants of different tissues are caused only by somatic (lifetime) mutations, then differences in mitochondrial DNA are caused by both somatic and germinal (germline) mutations.
Another difference is that the mitochondrial DNA molecule is circular, while nuclear DNA is packaged into chromosomes, which can (with some degree of convention) be considered as linear sequences of nucleotides.
Finally, the last feature of mitochondrial DNA that we will mention in this introductory section is its inability to recombine. In other words, the exchange of homologous (i.e., similar) regions is impossible between different evolutionary variants of mitochondrial DNA of the same species, and therefore the entire molecule changes only through slow mutation over thousands of years. In all chordates, mitochondria are inherited only from the mother, so the evolutionary tree of mitochondrial DNA corresponds to genealogy in the direct female line. However, this feature is not unique; in various evolutionary families, certain nuclear chromosomes are also not subject to recombination (having no pairs) and are inherited only from one of the parents. So. for example, the Y chromosome in mammals can only be passed on from father to son. Mitochondrial DNA is inherited only through the maternal line and is passed down from generation to generation exclusively by women. This special form of inheritance of the mitochondrial genome has made it possible to create a family tree of different human ethnic groups, locating our common ancestors in Ethiopia about 200,000 years ago. Possessing extraordinary abilities to adapt, with increasing Energy requirements Mitochondria are also able to multiply independently of cell division. This phenomenon is possible thanks to mitochondrial DNA. Mitochondrial DNA is transmitted exclusively by women. Mitochondrial DNA is not inherited according to Mendelian laws, but according to the laws of cytoplasmic inheritance. During fertilization, the sperm that penetrates the egg loses its flagellum, which contains all the mitochondria. Only the mitochondria contained in the mother's egg are transferred to the embryo. Thus, cells inherit their only source of energy from the mother's mitochondria. Mitochondria: the powerhouse of the cell. A unique source of energy. In everyday life, there are various ways to extract energy and use it for domestic needs: solar panels, nuclear power plants, wind power plants... The cell has only one solution for extracting, converting and storing energy: mitochondria. Only the mitochondrion can convert various types of energy into ATP, the energy used by the cell.
Cellular Energy Conversion Process Mitochondria use 80% of the oxygen we breathe to convert potential energy into energy usable by the cell. During the oxidation process, a large amount of energy is released, which is stored by mitochondria in the form of ATP molecules.
40 kg are converted per day. ATP Energy in a cell can take many forms. The principle of operation of the cellular mechanism is the conversion of potential energy into energy that can be directly used by the cell. Potential types of energy enter the cell through nutrition in the form of carbohydrates, fats and proteins. Cellular energy consists of a molecule called ATP: Adenosine triphosphate. It is synthesized as a result of the transformation of carbohydrates, fats and proteins inside the mitochondria. During the day, the equivalent of 40 kg of ATP is synthesized and decomposed in the adult human body. The following metabolic processes are localized in mitochondria: the conversion of pyruvate into acetyl-CoA, catalyzed by the pyruvate dehydrogenase complex: citrate cycle; the respiratory chain associated with ATP synthesis (the combination of these processes is called “oxidative phosphorylation”); the breakdown of fatty acids by oxidation and partly the urea cycle. Mitochondria also supply the cell with products of intermediate metabolism and act, along with the ER, as a depot of calcium ions, which, using ion pumps, maintains the Ca2+ concentration in the cytoplasm at a constant low level (below 1 µmol/l).
The main function of mitochondria is the capture of energy-rich substrates (fatty acids, pyruvate, the carbon skeleton of amino acids) from the cytoplasm and their oxidative breakdown with the formation of CO2 and H2O, coupled with the synthesis of ATP. Reactions of the citrate cycle lead to the complete oxidation of carbon-containing compounds (CO2) and the formation of reducing compounds equivalents, mainly in the form of reduced coenzymes. Most of these processes occur in the matrix. Respiratory chain enzymes that reoxidize reduced coenzymes are localized in the inner mitochondrial membrane. NADH and the enzyme-linked FADH2 are used as electron donors to reduce oxygen and form water. This highly exergonic reaction is multistep and involves the transfer of protons (H+) through the inner membrane from the matrix into the intermembrane space. As a result, an electrochemical gradient is created on the inner membrane. In mitochondria, the electrochemical gradient is used to synthesize ATP from ADP (ADP) and inorganic phosphate (Pi) catalyzed by ATP synthase. The electrochemical gradient is also the driving force behind a number of transport systems
215).http://www.chem.msu.su/rus/teaching/kolman/212.htm
The presence of its own DNA in mitochondria opens new avenues in research into the problem of aging, which may be related to the stability of mitochondria. In addition, mutation of mitochondrial DNA in known degenerative diseases (Alzheimer, Parkinson...) suggests that they may play a special role in these processes. Due to the constant sequential division of mitochondria aimed at producing energy, their DNA “wears out” . The supply of mitochondria in good shape is depleted, reducing the only source of cellular energy. Mitochondrial DNA is 10 times more sensitive to free radicals than nuclear DNA. Mutations caused by free radicals lead to mitochondrial dysfunction. But compared to the cell, the self-healing system of mitochondrial DNA is very weak. When damage to mitochondria is significant, they self-destruct. This process is called "autophagy".
In 2000, it was proven that mitochondria accelerate the process of photoaging. Areas of skin that are regularly exposed to sunlight have significantly higher rates of DNA mutations than areas that are protected. Comparison of biopsy results (taking skin samples for analysis) from an area of skin exposed to ultraviolet rays and a protected area shows that mitochondrial mutations due to UV exposure radiation causes chronic oxidative stress. Cells and mitochondria are forever linked: the energy supplied by mitochondria is necessary for cell activity. Maintaining mitochondrial activity is essential for better cellular activity and improved skin quality, especially facial skin that is too often exposed to UV rays.
Conclusion:
Damaged mitochondrial DNA within a few months gives rise to more than 30 similar mitochondria, i.e. with the same damage.
Weakened mitochondria cause a state of energy starvation in “host cells”, which results in a disruption of cellular metabolism.
Restoring the functions of metachondria and limiting the processes leading to aging is possible with the use of coenzyme Q10. As a result of the experiments, a slowdown in the aging process and an increase in life expectancy in some multicellular organisms was established as a result of the introduction of CoQ10 supplements.
Q10 (CoQ10) is the “spark plug” of the human body: just as a car cannot run without a starting spark, the human body cannot do without CoQ10. It is the most important component of mitochondria, producing the energy that cells need to divide, move, contract, and perform all other functions. CoQ10 also plays an important role in the production of adenosine triphosphate (ATP), the energy that powers all processes in the body. Moreover, CoQ10 is a very important antioxidant that protects cells from damage.
Although our bodies can produce CoQ10, they do not always produce enough of it. Since the brain and heart are among the most active tissues in the body, CoQ10 deficiency negatively affects them the most and can lead to serious problems with these organs. CoQ10 deficiency can be caused by a variety of reasons, including poor nutrition, genetic or acquired defects, and increased tissue demand, for example. Cardiovascular diseases, including high cholesterol levels and high blood pressure, also require increased tissue levels of CoQ10. Additionally, because CoQ10 levels decline with age, people over 50 may need more of it. Many studies have shown that a number of medications (primarily lipid-lowering drugs such as statins) reduce CoQ10 levels.
Given CoQ10's key role in mitochondrial function and cell protection, this coenzyme may be beneficial for a range of health problems. CoQ10 can benefit such a wide range of illnesses that there is no doubt about its importance as a nutrient. CoQ10 is not only a general antioxidant, but can also help with the following diseases:
Cardiovascular disease: high blood pressure, congestive heart failure, cardiomyopathy, protection during heart surgery, high cholesterol treated with medications, especially statins
Cancer (to enhance immune function and/or offset the side effects of chemotherapy)
Diabetes
Male infertility
Alzheimer's disease (prevention)
Parkinson's disease (prevention and treatment)
Periodontal disease
Macular degeneration
Animal and human studies have confirmed the benefits of CoQ10 for all of the above diseases, especially cardiovascular. In fact, studies have shown that 50 to 75 percent of people with various cardiovascular diseases suffer from CoQ10 deficiency in their heart tissue. Correcting this deficiency can often lead to dramatic results in patients with some type of heart disease. For example, CoQ10 deficiency has been shown to occur in 39 percent of patients with high blood pressure. This finding alone makes it necessary to take CoQ10 supplements. However, it appears that CoQ10's benefits extend beyond reversing cardiovascular disease.
A 2009 study published in the journal Pharmacology & Therapeutics suggests that the effects of CoQ10 on blood pressure are only noticeable 4 to 12 weeks after treatment, and the typical reduction in systolic and diastolic blood pressure in patients with high blood pressure is quite modest - within 10 percent.
Statin drugs, such as Crestor, Lipitor, and Zocor, work by inhibiting an enzyme that the liver needs to make cholesterol. Unfortunately, they also block the production of other substances necessary for the body to function, including CoQ10. This may explain the most common side effects of these drugs, especially fatigue and muscle pain. One large study, ENDOTACT, published in the International Journal of Cardiology in 2005, demonstrated that statin therapy significantly reduced plasma CoQ10 levels, but that this decline could be prevented by taking a 150 mg CoQ10 supplement. In addition, CoQ10 supplementation significantly improves the function of the lining of blood vessels, which is one of the key goals in the treatment and prevention of atherosclerosis.
In double-blind studies, CoQ10 supplementation was shown to be quite beneficial for some patients with Parkinson's disease. All patients in these studies had the three core symptoms of Parkinson's disease - tremors, rigidity and slowness of movement - and had been diagnosed with the disease within the past five years.
A 2005 study published in the Archives of Neurology also showed a slowing of functional decline in Parkinson's disease patients who took CoQ10. After initial screening and baseline blood tests, patients were randomized into four groups. Three groups received CoQ10 at different doses (300 mg, 600 mg and 1200 mg per day) for 16 months, while the fourth group received a placebo. The group that took the 1,200 mg dose showed less decline in mental and motor function and the ability to carry out daily activities such as feeding or dressing themselves. The greatest effect was noted in everyday life. The groups that received 300 mg and 600 mg per day developed less disability than those in the placebo group, but the results for members of these groups were less dramatic than those who received the highest dosage of the drug. These results indicate that the beneficial effects of CoQ10 in Parkinson's disease can be achieved at the highest doses of the drug. None of the patients experienced any significant side effects.
Coenzyme Q10 is very safe. No serious side effects have ever been reported, even with long-term use. Because safety has not been demonstrated during pregnancy and lactation, CoQ10 should not be used during these periods unless a physician determines that the clinical benefits outweigh the risks. I generally recommend taking 100 to 200 mg of CoQ10 per day. For best absorption, softgels should be taken with food. At higher dosage levels, it is better to take the drug in divided doses rather than in one dose (200 mg three times a day is better than 600 mg all at once).
Characteristic of the vast majority of cells. The main function is the oxidation of organic compounds and the production of ATP molecules from the released energy. The small mitochondrion is the main energy station of the entire body.
Origin of mitochondria
Today, there is a very popular opinion among scientists that mitochondria did not appear in the cell independently during evolution. Most likely, this happened due to the capture by a primitive cell, which at that time was not capable of independently using oxygen, of a bacterium that could do this and, accordingly, was an excellent source of energy. Such a symbiosis turned out to be successful and took hold in subsequent generations. This theory is supported by the presence of its own DNA in mitochondria.
How are mitochondria structured?
Mitochondria have two membranes: outer and inner. The main function of the outer membrane is to separate the organelle from the cell cytoplasm. It consists of a bilipid layer and proteins that penetrate it, through which the transport of molecules and ions necessary for work is carried out. While smooth, the inner one forms numerous folds - cristae, which significantly increase its area. The inner membrane is largely composed of proteins, including respiratory chain enzymes, transport proteins, and large ATP synthetase complexes. It is in this place that ATP synthesis occurs. Between the outer and inner membranes there is an intermembrane space with its inherent enzymes.
The inner space of mitochondria is called the matrix. Here are located the enzyme systems for the oxidation of fatty acids and pyruvate, enzymes of the Krebs cycle, as well as the hereditary material of mitochondria - DNA, RNA and the protein synthesizing apparatus.
What are mitochondria needed for?
The main function of mitochondria is the synthesis of a universal form of chemical energy - ATP. They also take part in the tricarboxylic acid cycle, converting pyruvate and fatty acids into acetyl-CoA and then oxidizing it. In this organelle, mitochondrial DNA is stored and inherited, encoding the reproduction of tRNA, rRNA and some proteins necessary for the normal functioning of mitochondria.
1 - outer membrane;
3 - matrix;
2 - internal membrane;
4 - perimitochondrial space.
The properties of mitochondria (proteins, structure) are encoded partly in the mitochondrial DNA and partly in the nucleus. Thus, the mitochondrial genome encodes ribosomal proteins and partly the electron transport chain carrier system, and the nuclear genome encodes information about the enzyme proteins of the Krebs cycle. A comparison of the size of mitochondrial DNA with the number and size of mitochondrial proteins shows that it contains information for almost half of the proteins. This allows us to consider mitochondria, like chloroplasts, to be semi-autonomous, that is, not completely dependent on the nucleus. They have their own DNA and their own protein-synthesizing system, and it is with them and with plastids that the so-called cytoplasmic inheritance is associated. In most cases, this is maternal inheritance, since the initial particles of mitochondria are localized in the egg. Thus, mitochondria are always formed from mitochondria. How to view mitochondria and chloroplasts from an evolutionary perspective has been widely debated. Back in 1921, the Russian botanist B.M. Kozo-Polyansky expressed the opinion that a cell is a symbiotrophic system in which several organisms coexist. Currently, the endosymbiotic theory of the origin of mitochondria and chloroplasts is generally accepted. According to this theory, mitochondria were independent organisms in the past. According to L. Margelis (1983), these could be eubacteria containing a number of respiratory enzymes. At a certain stage of evolution, they penetrated into a primitive cell containing a nucleus. It turned out that the DNA of mitochondria and chloroplasts in its structure differs sharply from the nuclear DNA of higher plants and is similar to bacterial DNA (circular structure, nucleotide sequence). The similarity is also found in the size of the ribosomes. They are smaller than cytoplasmic ribosomes. Protein synthesis in mitochondria, like bacterial synthesis, is suppressed by the antibiotic chloramphenicol, which does not affect protein synthesis on eukaryotic ribosomes. In addition, the electron transport system in bacteria is located in the plasma membrane, which resembles the organization of the electron transport chain in the inner mitochondrial membrane.