Everyone knows that humans are eukaryotes. This means that all its cells have an organelle that contains all the genetic information - the nucleus. However, there are exceptions. Are there nuclear-free cells in the human body and what is their significance for life?
Nuclear-free human cells
They cannot be compared with prokaryotes, which have a typical structure. What are these non-nuclear cells? There is no nucleus in blood cells - erythrocytes. Instead of this organelle, they contain a complex chemical complex of substances that allows them to perform the most important functions for the body. Platelets - platelets and lymphocytes - are also non-nuclear cells. There is no nucleus in the cells, which are called stem cells. All of these structures are united by one more feature. Since they lack a nucleus, they are unable to reproduce. This means that non-nuclear cells, examples of which were given, die after performing their function, and new ones are formed in specialized organs.
Erythrocytes
They determine the color of our blood. Non-nuclear blood cells, erythrocytes, have an unusual shape - a biconcave disk, which significantly increases their surface at a relatively small size. But their number is simply amazing: in 1 square. mm of their blood is up to 5 million! On average, an erythrocyte lives up to four months, after which it dies and is neutralized in the spleen and liver. New cells are formed every second in the red bone marrow.
RBC functions
What do these non-nuclear cells contain instead of a nucleus? These substances are called heme and globin. The first is iron-containing. It not only stains the blood red, but also forms unstable compounds with oxygen and carbon dioxide. Globin is a protein substance. Heme containing a charged iron ion is immersed in its large molecule. According to the mechanism of action, these cells can be compared with a fixed-route taxi. In the lungs, they add oxygen. With the blood flow, it is carried to all cells and released there. With the participation of oxygen, the process of oxidation of organic substances occurs with the release of a certain amount of energy that a person uses to carry out life. The vacated space is immediately occupied by carbon dioxide, which moves in the opposite direction - to the lungs, where it is exhaled. This process is a necessary condition for life. If oxygen is not supplied to the cells, their gradual death occurs. It can be life-threatening for the organism as a whole.
Erythrocytes perform another important function. On their membranesthere is a protein marker called the Rh factor. This indicator, like the blood type, is very important during blood transfusion, during pregnancy, donation and surgical operations. It must be installed, because in case of incompatibility, the so-called Rh conflict can occur. It is a protective reaction, but can lead to rejection of the fetus or organs.
Irrational nutrition, bad habits, polluted air can cause the destruction of red blood cells. As a result, a serious disease occurs, which is called anemia, or anemia. In this case, the person feels dizzy, weak, short of breath, tinnitus. Oxygen deficiency negatively affects the physical and mental activity of a person. It is especially dangerous during pregnancy. If insufficient oxygen is supplied to the fetus through the umbilical cord, this can lead to serious developmental disorders.
The structure of platelets
Nuclear-free cells platelets are also called platelets. In the inactive state, they really have a flat shape, reminiscent of a lens. But when the vessels are damaged, they swell, round, form unstable outgrowths of the outer layer - pseudopodia. Platelets are formed in the red bone marrow and do not live long - up to 10 days, neutralized in the spleen.
Clot formation process
The platelet matrix contains an enzyme called thromboplastin. In violation of the integrity of blood vesselsit is in plasma. Under its action, the blood protein prothrombin passes into its active form, in turn, acting on fibrinogen. As a result, this substance passes into an insoluble state. It turns into the protein fibrin. Its threads are closely intertwined and form a thrombus. The protective reaction of blood coagulation prevents blood loss. However, the formation of a blood clot inside the vessel is very dangerous. This can lead to its rupture and even death of the body. Violation of the clotting process is called hemophilia. This hereditary disease is characterized by an insufficient number of platelets and leads to excessive blood loss.
Stem cells
These non-nuclear cells are called stem cells for a reason. They are indeed the basis for all others. They are also called "genetically pure". Stem cells are found in all tissues and organs, but the bone marrow contains the most. They contribute to the restoration of integrity where necessary. Stem cells turn into any other types of cells when they are destroyed. It would seem that in the presence of such a magical mechanism, a person should live forever. Why doesn't this happen? The thing is that with age, the intensity of stem cell differentiation significantly decreases. They are no longer able to restore the destroyed tissue. But there is another danger as well. There is a high probability of stem cells turning into cancer cells, which will inevitably lead to the death of any living organism.
Nuclear-Free Cells: Examples and Features
Nuclear-free cells are quite common in nature. For example, blue-green algae and bacteria are prokaryotes. But, unlike nuclear-free human cells, they do not die after fulfilling their biological role. The fact is that prokaryotes have genetic material. Therefore, they are capable of division, which occurs by mitosis. As a result, two genetic copies of the mother cell are formed. The hereditary information of prokaryotes is represented by a circular DNA molecule, which doubles before dividing. This analogue of the nucleus is also called the nucleoid. In plants, the living cells of the conductive tissue - sieve tubes - are non-nuclear.
So, nuclear-free human cells are incapable of division, so they exist for a short period of time before performing their function. After that, their destruction and intracellular digestion occur. These include formed elements (erythrocytes), platelets (platelets), and stem cells.
