Everyone knows that a person is a eukaryote. This means that all its cells have an organelle in which all genetic information is contained - the nucleus. However, there are exceptions. Are there non-nuclear cells in the human body and what is their significance for life?
Human cell-free
They can not be compared with prokaryotes, which have a typical structure. What are these nuclear-free cells? There is no nucleus in the blood cells - red blood cells. Instead of this organelle, they contain a complex chemical complex of substances that allows them to perform the most important functions for the body. Blood platelets - platelets and lymphocytes - are also nuclear-free cells. There is no nucleus in cells called stem cells. All these structures are united by one more sign. Since they lack a core, they are not capable of reproduction. This means that nuclear-free cells, examples of which were given, die after performing their function, and new ones form in specialized organs.
Red blood cells
They determine the color of our blood. Nuclear-free blood cells erythrocytes have an unusual shape - a biconcave disk, which significantly increases their surface at relatively small sizes. But their number is simply amazing: in 1 square. mm of their blood is up to 5 million! On average, the red blood cell lives up to four months, after which it dies and is neutralized in the spleen and liver. New cells form every second in the red bone marrow.
Red blood cell function
What instead of the nucleus do these nuclear-free cells contain? These substances are called heme and globin. The first is iron-containing. It not only turns the blood red, but also forms unstable compounds with oxygen and carbon dioxide. Globin is a protein substance. A heme containing a charged iron ion is immersed in its large molecule. By the mechanism of action, these cells can be compared with a minibus. In the lungs they attach oxygen. With the flow of blood, it spreads to all cells and is 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 activities. The vacated spot is immediately occupied by carbon dioxide, which moves in the opposite direction - into the lungs, where it is exhaled. This process is a prerequisite for life. If oxygen does not enter the cells, they gradually die off. This can be life threatening to the body as a whole.
Red blood cells perform another important function. On their membranes 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 with incompatibility, the so-called Rhesus conflict can occur. It is a protective reaction, but can lead to rejection of the fetus or organs.
Poor nutrition, bad habits, polluted air can cause the destruction of red blood cells. As a result of this, a serious illness occurs, called anemia, or anemia. In this case, a person feels dizzy, weak, shortness 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 delivered to the fetus through the umbilical cord, this can lead to serious disturbances in its development.
Platelet structure
Nuclear-free cells platelets are also called blood platelets. When inactive, they do have a flat shape that resembles a lens. But when the vessels are damaged, they swell, round up, form unstable outgrowths of the outer layer - pseudopodia. Platelets form in the red bone marrow and do not live long - up to 10 days, rendering harmless in the spleen.
Thrombus formation process
The platelet matrix contains an enzyme called thromboplastin. If the integrity of the vessels is violated, it appears in the plasma. Under its action, the blood protein prothrombin passes into its active form, in turn, acting on fibrinogen. As a result, this substance goes into an insoluble state. It turns into fibrin protein. Its threads are closely intertwined and form a blood clot. A protective coagulation reaction 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. Coagulation is called hemophilia. This hereditary disease is characterized by insufficient platelet count and leads to excessive blood loss.
Stem cells
These nuclear-free cells are called stem cells for good reason. They really are the foundation for all others. They are also called "genetically pure." Stem cells are found in all tissues and organs, but the bone marrow contains most of them. They help restore integrity where necessary. Stem cells turn into any other types of cells when they are destroyed. It would seem that with such a magical mechanism a person should live forever. Why is this not happening? The thing is that with age, the intensity of stem cell differentiation decreases significantly. They are already unable to repair damaged tissue. But there is one more danger. There is a high probability of the conversion of stem cells into cancer cells, which will inevitably lead to the death of any living organism.
Nuclear-free cells: examples and features of difference
In nature, nuclear-free cells are quite common. For example, blue-green algae and bacteria are prokaryotic. But, unlike human nuclear-free 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 through mitosis. As a result, two genetic copies of the mother cell are formed. Hereditary information of prokaryotes is represented by a circular DNA molecule that doubles before division. This nucleus analog is also called a nucleoid. In plants, the living cells of the conductive tissue — sieve tubes — are nuclear-free .
So, non-nuclear human cells are incapable of division, so they exist for a short period of time before performing their function. After this, their destruction and intracellular digestion occurs. These include shaped elements (red blood cells), blood platelets (platelets), and stem cells.