Apoptosis

Definition

noun, plural: apoptoses

A programmed cell death involving an ordered sequence of biochemical events that result in cell changes (e.g. blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, chromosomal DNA fragmentation, etc.)


Supplement

The death of a cell may be physiological (i.e. programmed cell death) or non-physiological (i.e. necrosis). In the former, it is described as physiological because the death of the cell is mediated by an intracellular program.1 The programmed type of cell death is further categorized into type I cell death (or apoptosis) and type II cell death (or autophagy).

Apoptosis is a programmed cell death as signaled by the nuclei in normally functioning human and animal cells when age or state of cell health and condition dictates. It is an active process requiring metabolic activity by the dying cell, often characterised by cleavage of the DNA into fragments that give a so called laddering pattern on gels. The various morphological changes of the cell undergoing apoptosis are blebbing, cell shrinkage, chromatin condensation, nuclear fragmentation, chromosomal DNA fragmentation, and global mRNA decay.2

Cells that die by apoptosis do not usually elicit the inflammatory responses that are associated with necrosis, though the reasons are not clear. Cancerous cells, however, are unable to experience the normal cell transduction or apoptosis-driven natural cell death process.

Apoptosis is essential, for instance during embryonic development. An example is during human fetal development wherein the cells between the fingers of the fetus undergo apoptotic cell death so that the digits would not remain fused but separate.


Word origin: Ancient Greek apóptōsis (“a falling off”), apó (“away from”) + ptôsis (“falling”)

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Reference(s):
1 Engelberg-Kulka H, Amitai S, Kolodkin-Gal I, Hazan R (2006). "Bacterial Programmed Cell Death and Multicellular Behavior in Bacteria". PLoS Genetics 2 (10): e135.
2 Apoptosis. Retrieved from [[1]].

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