All cells live and die. Cell death occurs in two ways. One of them is death by injury. An external factor can damage and kill cells; for example, too high or too low heat, toxic chemicals, microbes or mechanical injury. Intracellular control mechanisms have no effect on this type of cell death.
In other words, the cell does not die of its own accord. Another form of cell death is a programmed cell death called “apoptosis”. Apoptosis is when the cell kills itself, that is, commits suicide. This suicide is usually due to two reasons. The first is to make room for newly formed and more necessary cells. For example, in the newly formed fetus, the cells between the fingers destroy themselves over time, resulting in a normal hand shape.
Another example of apoptosis is that the inner surface of the uterus, which is prepared for pregnancy, destroys itself when there is no fertilization, which causes menstrual bleeding that occurs every month in women. This type of programmed cell death is considered a physiological, that is, a normal constitutional change.
Another reason for cell suicide is that the cell becomes useless due to the deterioration in it. The cell, which is so damaged that it cannot continue its normal life, decides to commit suicide instead of multiplying with this damage. For example, a cell infected with a harmful virus kills itself when it cannot get rid of it. Killer T cells, which are activated when a foreign molecule enters the body, destroy themselves after this molecule is destroyed, that is, after their task is over.
Thus, activated killer T cells are prevented from attacking other healthy cells of the body. Another important reason that triggers cell suicide is damage to cell DNA. As cells reproduce, DNA, made up of millions of molecules, is rapidly replicating itself. An error of one in a million or less can occur during the replication of DNA.
Since such errors can lead to the formation of genetically altered cells, these cells are immediately destroyed. It is very important for the continuity of life to destroy cells that are unable to function or cancerous. Every day, hundreds of faulty cells are formed and they are killed immediately. Apoptosis is the most important key mechanism in the destruction of these cells.
The cell’s understanding when to kill itself also depends on a very complex mechanism. Programmed death is initiated by signals from inside or outside the cell. Mitochondria, the energy production center in the cell, also control cell death. The damage that occurs in the cell is perceived by the proteins in the outer membrane of the mitochondria, and after that, it begins to secrete various proteins.
These proteins come out of the mitochondrial membrane and diffuse into the cell. Proteins that accumulate in the cell and have disintegrating properties can initiate other building blocks of the cell, as well as programmed cell death. When receptors such as “FAS” and “TNF” are stimulated, molecules called “caspases” are activated and the cell is destroyed. Signals from outside the cell sometimes lead to the synthesis of a protein in mitochondria that initiates apoptosis.
This protein, called AIF (Apoptosis – Inducing Factor), passes into the cell after being synthesized in the mitochondria and initiates apoptosis. Cell suicide is essential for survival. It is very important for cells that have expired, completed their task or been damaged to self-destruct and for other cells to live healthy. Apoptosis is the most important mechanism preventing cancer.
Cell Control Mechanism
Apoptosis prevents viruses that enter our body from settling in our cells and causing various diseases, including cancer. Besides all its benefits, apoptosis is a mechanism that limits human lifespan. Cell control mechanisms are like double-edged swords. On the one hand, it destroys useless harmful cells, on the other hand, it limits the life span of the organism.
By destroying the apoptosis feature, the life span of the cells can be extended, but in this case, cancerization of the cells may not be prevented. Currently, our knowledge of cell control mechanisms is limited. While it changes the control mechanisms that destroy the damaged cells and make room for the necessary cells and extend the life span, there is a possibility of losing the control of the cell completely.
Today’s technology and modern science have not yet established absolute dominance over natural control systems. It seems doubtful whether this dominance will be fully established in the near future.
Normal dendritic cells in the immune system commit suicide when they stay in the same culture as melanoma (skin cancer) cells for 48 hours. Apoptosis occurs in the form of cell shrinkage, condensation of the intracellular fluid, disintegration of the membrane, condensation of genetic material and fragmentation of the nucleus.