CELL DEATH
Many of our cells are programmed to commit suicide, for good reasons.
A healthy body not only depends on cells’ ability to grow and divide, but also on their ability to destroy themselves once they are no longer needed. This happens during the embryonic stage, or when cells are damaged, old or infected by a virus. The phenomenon is known as apoptosis, or programmed cell death.
Apoptosis is the human body’s natural mechanism for removing damaged or worn-out cells. The programmed cell death of such cells prevents unintentional body growth, and contributes to maintaining a fairly constant number of cells in the body.
Cells can die in two ways: either they are killed by damage through infection, or they are persuaded to commit suicide. Apoptosis happens when old cells need to be renewed, when damaged cells can’t be repaired so must be removed, when virus-infected cells must be destroyed, or when cells are subjected to stress and hunger.
Apoptosis is also important in the embryonic stage. Apoptosis removes tissue and cells when the embryo’s fingers and toes are formed, and it removes surplus cells when synapses are developed between brain neurons. The process takes place in billions of cells every day, as surface cells of mucosa, the stomach, intestines and skin are replaced regularly by new ones.
Apoptosis is a necessary tool for destroying cells that make up a threat to the body’s condition. Cells infected by viruses are killed via the immune system’s T cells, which induce the cells into a programmed death.
The apoptosis mechanism not functioning optimally can lead to auto-immune diseases by which the immune system attacks its own body. This is because after a case of infection, the millions of immune cells that were produced to fight it must also be eliminated to avoid the scenario where they attack healthy body cells.
Finally, cells with DNA that has been damaged by radiation or toxic chemicals will stimulate their own apoptosis and kill themselves in order not to develop into cancer cells.
Apoptosis happens as a result of a highly controlled internal suicide program in all cells. The mechanism involves a series of biochemical reactions that cause changes in the cell’s appearance: the cell surface becomes full of holes and it shrinks; cell fragments unite in membranes; the nucleus crumbles, the chromosomes condense, and the DNA goes to pieces. The process is closely regulated and aims to leave neither toxic cell remnants nor the chance of re-infection.