Mitochondria are one of the most important components of any cell. They are also called chondriosomes. These are granular or filamentous organelles that are an integral part of the cytoplasm of plants and animals. They are the producers of ATP molecules, which are so necessary for many processes in the cell.
What are mitochondria?
Mitochondria are the energy base of cells, their activity is based on the oxidation of organic compounds and the use of energy released during the breakdown of ATP molecules. Biologists in simple language call it a station for generating energy for cells.
In 1850, mitochondria were identified as granules in muscles. Their number varied depending on the growth conditions: they accumulate more in those cells where there is a large oxygen deficiency. This happens most often during physical exertion. In such tissues, there is an acute lack of energy, which is replenished by mitochondria.
The appearance of the term and place in the theory of symbiogenesis
In 1897, Bend first introduced the concept of "mitochondria" to denote the granular and filamentous structure in the cytoplasm of cells. In shape and size theyare diverse: the thickness is 0.6 microns, the length is from 1 to 11 microns. In rare situations, mitochondria can be large and branched.
The theory of symbiogenesis gives a clear idea of what mitochondria are and how they appeared in cells. It says that the chondriosome arose in the process of being damaged by bacterial cells, prokaryotes. Since they could not autonomously use oxygen to generate energy, this prevented their full development, and progenots could develop unhindered. In the course of evolution, the connection between them made it possible for progenotes to pass on their genes to now eukaryotes. Thanks to this progress, mitochondria are no longer independent organisms. Their gene pool cannot be fully realized, as it is partially blocked by enzymes that are in any cell.
Where do they live?
Mitochondria are concentrated in those areas of the cytoplasm where there is a need for ATP. For example, in the muscle tissue of the heart, they are located near the myofibrils, and in spermatozoa they form a protective disguise around the axis of the tourniquet. There they produce a lot of energy in order for the "tail" to spin. This is how the sperm moves towards the egg.
In cells, new mitochondria are formed by simple division of previous organelles. During it, all hereditary information is preserved.
Mitochondria: what they look like
The shape of the mitochondria resembles a cylinder. They are often found in eukaryotes, occupying from 10 to 21% of the cell volume. Their sizes andthe forms differ in many respects and can change depending on the conditions, but the width is constant: 0.5-1 microns. The movements of chondriosomes depend on the places in the cell where the rapid expenditure of energy takes place. Move through the cytoplasm, using the structures of the cytoskeleton to move.
Replacing mitochondria of different sizes, working separately from each other and supplying energy to certain areas of the cytoplasm, are long and branched mitochondria. They are able to provide energy to areas of cells that are far from each other. Such joint work of chondriosomes is observed not only in unicellular organisms, but also in multicellular organisms. The most complex structure of chondriosomes occurs in mammalian skeletal muscles, where the largest branched chondriosomes are joined to each other using intermitochondrial junctions (IMCs).
They are narrow gaps between adjacent mitochondrial membranes. This space has a high electron density. MMK are more common in heart muscle cells, where they bind together with working chondriosomes.
To better understand the issue, you need to briefly describe the significance of mitochondria, the structure and functions of these amazing organelles.
How are they made?
To understand what mitochondria are, you need to know their structure. This unusual source of energy is shaped like a ball, but more often elongated. The two membranes are close together:
- outer (smooth);
- internal,which forms outgrowths of leaf-shaped (cristae) and tubular (tubules) shape.
If you do not take into account the size and shape of mitochondria, they have the same structure and function. The chondriosome is delimited by two membranes, 6 nm in size. The outer membrane of the mitochondria resembles a container that protects them from the hyaloplasm. The inner membrane is separated from the outer one by a section 11–19 nm wide. A distinctive feature of the inner membrane is its ability to protrude into the mitochondria, taking the form of flattened ridges.
The inner cavity of the mitochondria is filled with a matrix, which has a fine-grained structure, where threads and granules (15-20 nm) are sometimes found. The threads of the matrix create organelle DNA molecules, and small granules create mitochondrial ribosomes.
ATP synthesis at the first stage takes place in the hyaloplasm. At this stage, there is an initial oxidation of substrates or glucose to pyruvic acid. These procedures take place without oxygen - anaerobic oxidation. The next stage of energy production is the aerobic oxidation and breakdown of ATP, this process occurs in the mitochondria of cells.
What do mitochondria do?
The main functions of this organelle are:
- energy production for cells;
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storage of hereditary information in the form of one's own DNA.
happens in mitochondria
The presence of its own deoxyribonucleic acid in mitochondria once again confirms the symbiotic theory of the appearance of theseorganelles. Also, in addition to the main work, they are involved in the synthesis of hormones and amino acids.
Mitochondrial pathology
Mutations occurring in the genome of the mitochondria lead to depressing consequences. The carrier of human hereditary information is DNA, which is transmitted to descendants from parents, and the mitochondrial genome is transmitted only from the mother. This fact is explained very simply: children receive cytoplasm with chondriosomes enclosed in it together with a female egg, they are absent in spermatozoa. Women with this disorder can pass on a mitochondrial disease to their offspring, but a sick man cannot.
Under normal conditions, chondriosomes have the same copy of DNA - homoplasmy. Mutations can occur in the mitochondrial genome, due to the coexistence of he althy and mutated cells, heteroplasmy occurs.
Thanks to modern medicine, more than 200 diseases have been identified to date, the cause of which was a mitochondrial DNA mutation. Not in all cases, but mitochondrial diseases respond well to therapeutic maintenance and treatment.
So we figured out the question of what mitochondria are. Like all other organelles, they are very important for the cell. They indirectly take part in all processes that require energy.
