The Mitochondria Are small organelles (parts of the cell that have a specific function) that are responsible for decomposing nutrients and create molecules full of energy in the form of ATP (adenosine triphosphate, a special molecule), which is later used by cells.
For this reason, it is said that mitochondria act as the cellular digestive system, and can be compared to the electrical system that provides electrical energy to a shopping center or a city, that is, a source of power.
An electrical generator system uses a fuel to"create"electricity. The larger the city, the more energy it will need.
Similarly, if the cells are more active, they require a greater amount of mitochondria.
To produce ATP, mitochondria perform the process called cellular respiration. Mitochondria take food molecules in the form of carbohydrates and combine them with oxygen to result in ATP. They use proteins called enzymes for the correct chemical reaction to occur.
Cellular respiration breaks down the substances into simpler compounds (carbon dioxide and water), and this is where the release of energy that provides the body occurs.
These organelles called mitochondria float freely in all Eukaryotic cells , Both animal and vegetable.
Some cells, such as Erythrocytes (Red blood cells) do not contain mitochondria. Their number can vary from one to 10,000, depending on the type of cell.
In the case of muscle cells, which require a lot of energy, they are more abundant. On the other hand, neurons do not need as much energy therefore they have a smaller amount of mitochondria.
Mitochondria are able to rapidly change shape (elliptical or oval) as well as move within the cell if necessary.
Even if the cell is not getting enough energy, they can reproduce by becoming larger and then dividing in a process called binary fission.
Conversely, if the cell needs a smaller amount of energy, some mitochondria become inactive or die.
Parties. Structure of mitochondria
Mitochondria are dynamic in character and constantly merge to form chains and then separate. They typically have a capsule-like shape when viewed individually.
With the help of the electron microscope, it has been possible to define the following parts of the mitochondria:
Outer membrane
It is completely permeable to small molecules. Of smooth surface, it contains special channels that transport molecules of greater size. It also serves as protection and its shape varies from round to elongated.
In it are porinas, special proteins that fulfill the function of pores (hence its name) through which other molecules can pass in turn.
Internal Membrane
Also called the"intermitocondrial membrane". It is less permeable than the outer one, that is, it only lets much smaller molecules pass through the matrix.
In it are observed folds that are called"crests". Many of the chemical reactions that occur in the mitochondria, take place specifically in the inner membrane.
This membrane contains the electron transport system, whereby these are carried from one protein component to the next, forming a chain.
Intermembranous Space
It is the space that exists between the outer and inner membranes. Also called"cavity".
It is characterized by having a high concentration of protons, due to the presence of the electron transport system in the inner membrane.
This space is approximately 70 ångström, ie 7 x 10-9 meters (0.000000007 m).
Crests
They are folds of the inner membrane and help to increase the surface area, so that more chemical reactions such as electron transport and cellular respiration can occur.
If these folds do not exist, the inner membrane would simply be a spherical surface where less chemical reactions would occur and would therefore be a much less efficient structure.
Matrix
It is the fluid, resembling a gel, that is contained within the mitochondria. It contains a mixture of high concentration of enzymes and in it occurs the so-called Krebs cycle, in which nutrients are metabolized, turning them into by-products that mitochondria can use to produce energy.
In the matrix of the mitochondria are observed Ribosomes Which have the function of synthesizing proteins.
Another feature of the matrix is the presence of mitochondrial DNA, ie, its own genetic material. In addition, it can produce its own ribonucleic acids (RNA) and proteins. Mitochondrial DNA is necessary for the synthesis of many proteins.
Also in the matrix are structures called granules, which are still under study by cellular biologists. It is believed that they can control concentrations of ions.
Functions
Mitochondria fulfill more than one function. Some are considered primary and others secondary.
Energy production
It is the most important function of mitochondria. Although one speaks of"producing"or"creating"energy, many authors prefer to use the term"liberate", because what actually happens is a release of stored energy thanks to the chemical reactions that take place in the mitochondria.
As mentioned above, the energy released is represented by the ATP molecules.
This happens through a process of cellular respiration, also called aerobic respiration, because it depends on the presence of oxygen. This process has 3 stages that are:
- Glycolysis, or the separation of sugar molecules
- Krebs cycle, a process in which proteins and fats are assimilated according to the selection between what is productive or not for the body.
- Electron transport
Heat Production
The process of thermogenesis or heat production is present in living organisms, especially in mammals. According to the way in which the heat production starts, it is classified in:
- Thermogenesis associated with exercise, ie, due to movement (eg, shivering).
- Non-exercise thermogenesis (movement) within which non-shivering thermogenesis is included.
- Diet-induced thermogenesis.
In this sense, non-shivering thermogenesis occurs in the matrix of the mitochondria. It is due to the"leak"of protons that sometimes occurs under certain conditions and when given, the result is the release of proton energy in the form of heat.
Non-shivering thermogenesis occurs more frequently in those organisms with brown adipose tissue, such as bears that live in cold climates, which hibernate during the coldest seasons.
Contribution to the apoptosis process
Apoptosis is nothing more than the programmed cell death process, which is beneficial to organisms since it allows the control of cell growth, destroying those that are not necessary.
For example, during the formation of the human embryo, the differentiation of the fingers occurs by apoptosis, eliminating the cells that are between the fingers which results in the separation of the same.
Likewise, this process is of great help in the normal formation of organs, the destruction of cells infected by viruses or cancer cells.
Mitochondria help ensure that the right cells survive and eliminate those that are not needed by facilitating apoptosis.
Calcium Storage
Mitochondria are important"containers"in which calcium ions are stored and the concentration of this mineral plays an essential role in cellular functioning.
These amounts should be accurately controlled to avoid overloads that may affect the function of the cells.
Mitochondria also act as regulators of calcium quantities and avoid these overloads.
Contribution to the synthesis of certain hormones
Mitochondria are involved in the production of hormones such as estrogen and Testosterone .
Associated diseases
As mentioned above, the main function of the mitochondria is to release the energy necessary for the body to be maintained and the processes of growth occur.
It may happen that mitochondria do not release enough energy, thus causing injury or even cell death.
When this happens throughout the body, each of the body's systems begins to fail, which puts the person's life at risk.
Among the organs and systems that may be affected by mitochondrial disease are:
- Pancreas (Diabetes)
- Liver (Liver disease)
- Kidneys
- Muscles (Weakness, Pain)
- Heart
- Eyes (Blindness, cataracts)
- Brain (Tremors, motor problems,
- Ears (Deafness)
- Endocrine system
- Respiratory system
This is because they require a greater amount of energy to function properly.
This type of affections are due to the little or no production of the proteins that are generated in mitochondria and that also are related to the metabolism.
The origin of these alterations is some type of mutation in the DNA present in the mitochondria. In spite of the little contribution of this to the human genome, they have quite broad effects in each one of the systems mentioned above.
Other studies have linked several neurological diseases such as Parkinson's , With alterations of the genes that are related to the mitochondrial function, since the tissues affected by the disease require the energetic contribution of the mitochondria.
References
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- What is mitochondria and what are its functions? Retrieved from:
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- Cells-Mitochondria. Retrieved from: kidsbiology.com.
- Mitochondrial Diseases. Retrieved from: tsbvi.edu.
- Function of Mitochondria. Retrieved from: ivyroses.com.
- López, M. and Pereda, S. (2013). Biology 1st Middle Education. Santiago de Chile, Santillana del Pacífico S. of Ediciones.
- Structure of Mitochondria. Retrieved from: ivyroses.com.
- Vidyasagar, A. (2015). Live Science: What Are Mitochondria? Retrieved from: livescience.com.
- Rogers, K. Enclyclopaedia Britannica: Mitochondrion. Retrieved from: britannica.com.
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