What are the special features of mitochondrial inheritance?

Mitochondria are a cell compartment that is inherited maternally. All children of a mother therefore have the same mitochondrial DNA (abbreviated as mtDNA). This fact can be used in genealogical research by using mitochondrial DNA to determine, for example, the membership of a family to a people.

Furthermore, mitochondria with their mtDNA are not subject to a strict division mechanism, as is the case with DNA within our cell nucleus. While the DNA is doubled and then transferred to the daughter cell to exactly 50%, the mitochondrial DNA is replicated more or less during the cell cycle and is also distributed unevenly to the newly developing mitochondria of the daughter cell. The mitochondria usually contain two to ten copies of mtDNA within their matrix.

The purely maternal origin of the mitochondria can be explained by our germ cells. Since the male sperm, when united with the egg cell, only transfers its head, which contains only the DNA from the cell nucleus, the maternal egg cell contributes all mitochondria for the formation of the later embryo. The tail of the sperm, at the front end of which the mitochondria are located, remains outside the egg, as it is only used by the sperm to move around.

Function of mitochondria

The term “power plants of the cell” strikingly describes the function of the mitochondria, namely energy production. All energy sources from food are metabolized here in the last step and converted into chemical or biologically usable energy. The key to this is called ATP (Adenosine Tri-Phosphate), a chemical compound that can store a lot of energy and release it again through decomposition.

ATP is the universal energy supplier for all processes in any cell, it is needed almost always and everywhere. In the matrix, i.e. the space inside the mitochondrion, the last metabolic steps for the utilization of carbohydrates or sugar (so-called cell respiration, see below) and fats (so-called beta-oxidation) take place. Proteins are ultimately also utilized here, but they are already converted into sugars in the liver and therefore also take the path of cellular respiration.

Mitochondria are thus the interface for the conversion of food into larger quantities of biologically usable energy. There are many mitochondria per cell. Roughly speaking, one can say that a cell that needs a lot of energy, such as muscle and nerve cells, also has more mitochondria than a cell whose energy turnover is lower.

Mitochondria can initiate programmed cell death (apoptosis) via the intrinsic signaling pathway (intercellular). A further task is the storage of calcium. Cell respiration is a chemically extremely complex process for the conversion of carbohydrates or fats to ATP, the universal energy carrier, with the help of oxygen.

It is divided into four process units, which in turn consist of a large number of individual chemical reactions: Glycolysis, PDH (pyruvate dehydrogenase) reaction, citrate cycle and respiratory chain. Glycolysis is the only part of cell respiration that takes place in the cell plasma, the rest takes place in the mitochondria. Glycolysis already produces small amounts of ATP, so that cells without mitochondria or without oxygen supply can meet their energy requirements.

However, this type of energy production is much more inefficient in relation to the sugar used. Two ATPs can be obtained from one sugar molecule without mitochondria, but with the help of mitochondria a total of 32 ATPs can be obtained. The structure of the mitochondria is decisive for the further steps in cellular respiration.

PDH reaction and citrate cycle take place in the mitochondrial matrix. For this purpose, the intermediate product of glycolysis is actively transported via transporters in the two membranes into the interior of the mitochondria for further utilization. The last step of cell respiration, the respiratory chain, then takes place in the inner membrane and uses the strict separation of the space between the membranes and the matrix.This is also where the oxygen we inhale comes into play, which is the last important factor for a functioning energy production.

Physical and mental stress can reduce the performance of our mitochondria and thus our body. You can try to strengthen your mitochondria with simple means. From a medical point of view, this is still controversial, but there are now some studies that attribute a positive effect to some methods.

A balanced diet is also important for mitochondria. A balanced electrolyte balance is particularly relevant. This includes above all sodium and potassium, sufficient vitamin B12 and other B vitamins, omega3 fatty acids, iron and the so-called coenzyme Q10, which forms part of the respiratory chain in the inner membrane.

Sufficient exercise and sport stimulates the division and thus proliferation of mitochondria, as they now have to produce more energy. This is also noticeable in everyday life. Some studies show that exposure to cold, e.g. taking a cold shower, also promotes the division of mitochondria.

More controversial are diets such as a ketogenic diet (no carbohydrates) or intermittent fasting. Before such measures one should always consult one’s doctor of confidence. Particularly with heavy illnesses, like cancer, one should be careful with such experiments. However, general measures, such as sports and a balanced diet, never harm and also demonstrably strengthen the mitochondria in our body.