Apoptosis facts for kids

Apoptosis is the controlled death of a cell. It plays an integral part of tissue development. During limb development in a foetus, apoptosis allows body digits (fingers and toes) to separate from each other. The process is most prevalent until puberty begins. The rate of apoptosis should be balanced by the rate of cell production via mitosis.

Discovery

The phenomenon of programmed cell death was first described by Carl Vogt in 1842. However, it was only in 1965 that John Foxton Ross Kerr researched the idea extensively. Using electron microscopy, he was successfully able to distinguish between necrosis and apoptosis. He then joined the research team of Professor Currie and Andrew Wyllie who, in 1972, published a report on their findings in the British Journal of Cancer. They used the term "apoptosis" as used by Hippocrates to mean "bones falling off".

Sequence of events in apoptosis

When a cell dies by apoptosis, surrounding tissue is not harmed.
1. Enzymes break down the cytoskeleton of the cell.
2. Cytoplasm becomes dense, with organelles tightly packed.
3. Cell surface membrane forms "blebs".
4. Chromatin condenses and the nuclear envelope breaks. DNA breaks into fragments.
5. The cell breaks down into vesicles, taken up by phagocytosis.

Controlling the cell cycle

Apoptosis is the normal end of a cell's life. At any point in time, there may be too many cells in one area, and the DNA coding for apoptosis will activate in some of those cells and they will die safely. This is important to the overall functioning of the organism. If, for example, the making of liver cells were to speed up and they never died, the liver would no longer function properly. The liver cells would eventually take over the organism's body. Apoptosis takes place by the help of lysosomes. Lysosomes rupture when the cell is old or damaged, this lets out digestive enzymes all over the cell and digests it, therefore killing the cell.

Cancer

Cancerous cells do not undergo apoptosis, and that is why they are such a problem. They continuously multiply until the host organ or the organism's body cannot function anymore. This occurs because the apoptosis coding has mutated and so has other coding. This causes rapid mitotic division of the unwanted cells. This is a cancerous growth.

Images for kids

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  John Sulston won the Nobel Prize in Medicine in 2002, for his pioneering research on apoptosis.

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  Overview of signal transduction pathways.

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  Different steps in apoptotic cell disassembly.

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  Long-term live cell imaging (12h) of multinucleated mouse pre-Adipocyte trying to undergo mitosis. Due to the excess of genetic material the cell fails to replicate and dies by apoptosis.

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  A section of mouse liver showing several apoptotic cells, indicated by arrows

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  A section of mouse liver stained to show cells undergoing apoptosis (orange)

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  Neonatal cardiomyocytes ultrastructure after anoxia-reoxygenation.

See also

In Spanish: Apoptosis para niños