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Subject - Biochemistry

Apoptosis, programmed cell death, is the result of a suicide order from the cell. The signal triggering death may come from the cell itself or from T lymphocytes in the immune system.

Cells have molecular security systems that check to make sure the cell is functioning normally. If a cell is infected by a virus, for example, or is degenerate and involved in tumor formation, the cell tries to trigger self-destruction. When there is massive damage to the DNA, proteins like p53 act to initiate apoptosis.

T cells are also able to prompt programmed cell death of a target cell. If the staggered suicide security systems are switched off, e.g. by multiple mutations, infected or degenerate cells usually give themselves away by means of the proteins they produce, fragments of which the cells present for monitoring by the T cells in the MHC. If a T cell decides that the examined cell is producing foreign or defective proteins, it can actively kill the cell or initiate its suicide, e.g. with tumor necrosis factor.

In a healthy organism, apoptosis is used as a means to regulate embryonic development and tissue growth, as well as regeneration of tissue and selection of germ cells and immune cells.