So long, cells
Cells die in a variety of ways
Cells, like people, die if they are starved or poisoned. Blockage of the coronary artery in the heart causes death of heart muscle cells in a heart attack, for instance. A similar obstruction in the carotid artery, which supplies the brain, leads to the destruction of brain cells in a stroke. This kind of death is called necrosis, but a cell’s life can also end in other ways.
One is programmed cell death, or apoptosis. Cells have an inbuilt self-destruct routine that keeps them poised on the brink of suicide. Normally, signals from neighbouring cells keep them from doing themselves in, but if the signals change, the cell pushes the suicide button.
This is a neat and tidy death. Whereas necrotic cells swell and burst, spilling lysosomal enzymes and damaging surrounding cells, apoptosis involves the orderly dismantling of organelles and proteins: the cell shrinks and ends up as a few vesicles, which are cleared up by other cells.
Apoptosis happens in different places at different times. The developing embryo uses it to sculpt fingers from a web-shaped hand, by removing the cells in between the fingers. Cells with damaged DNA may sense the damage and sacrifice themselves for the common good, as in the case of sunburn. In this way, apoptosis may prevent skin cancer. Viruses may also set off apoptosis in infected cells. Triggering apoptosis is one way that HIV depletes the immune system of vital defensive cells.Lead image:
Paul Andrews, Univ. Dundee/Wellcome Images
- Check out this interactive animation about necrosis and apoptosis
- Find out more about the differences between apoptosis and necrosis
- So long, cells PDF [PDF 527KB]