2,851
edits
Apoptosis: Difference between revisions
no edit summary
No edit summary |
|||
| Line 1: | Line 1: | ||
'''Apoptosis''' is a form of [[wikipedia:Programmed_cell_death|programmed cell death]] that occurs in [[wikipedia:Multicellular_organism|multicellular organisms]] and in some eukaryotic, single-celled microorganisms such as [[wikipedia:Yeast|yeast]].<ref>{{cite book|vauthors=Green D|title=Means to an End: Apoptosis and other Cell Death Mechanisms|year=2011|publisher=Cold Spring Harbor Laboratory Press|location=Cold Spring Harbor, NY|isbn=978-0-87969-888-1|url=https://books.google.com/books?id=s8jBcQAACAAJ|access-date=2020-05-25|archive-date=2020-07-26|archive-url=https://web.archive.org/web/20200726071718/https://books.google.com/books?id=s8jBcQAACAAJ|url-status=live}}</ref> [[wikipedia:Biochemistry|Biochemical]] events lead to characteristic cell changes ([[wikipedia:Morphology_(biology)|morphology]]) and death. | '''Apoptosis''' is a form of [[wikipedia:Programmed_cell_death|programmed cell death]] that occurs in [[wikipedia:Multicellular_organism|multicellular organisms]] and in some eukaryotic, single-celled microorganisms such as [[wikipedia:Yeast|yeast]].<ref>{{cite book|vauthors=Green D|title=Means to an End: Apoptosis and other Cell Death Mechanisms|year=2011|publisher=Cold Spring Harbor Laboratory Press|location=Cold Spring Harbor, NY|isbn=978-0-87969-888-1|url=https://books.google.com/books?id=s8jBcQAACAAJ|access-date=2020-05-25|archive-date=2020-07-26|archive-url=https://web.archive.org/web/20200726071718/https://books.google.com/books?id=s8jBcQAACAAJ|url-status=live}}</ref> [[wikipedia:Biochemistry|Biochemical]] events lead to characteristic cell changes ([[wikipedia:Morphology_(biology)|morphology]]) and death.{{pmid|14499155}} These changes include [[wikipedia:Bleb_(cell_biology)|blebbing]], [[wikipedia:Plasmolysis|cell shrinkage]], [[wikipedia:Karyorrhexis|nuclear fragmentation]], [[wikipedia:Pyknosis|chromatin condensation]], [[wikipedia:Apoptotic_DNA_fragmentation|DNA fragmentation]], and [[wikipedia:MRNA|mRNA]] decay. The average adult human loses between 50 and 70 [[wikipedia:1,000,000,000|billion]] cells each day due to apoptosis. That is around 0.5% of the 13 [[Wikipedia:1,000,000,000,000|trillion]] cells of an average human adult. For an average human child between eight and fourteen years old, each day the approximate lost is 20 to 30 billion cells.<ref>{{cite book|vauthors=Karam JA|title=Apoptosis in Carcinogenesis and Chemotherapy|year=2009|publisher=Springer|location=Netherlands|isbn=978-1-4020-9597-9}}</ref> | ||
In contrast to [[wikipedia:Necrosis|necrosis]], which is a form of traumatic cell death that results from acute cellular injury, apoptosis is a highly regulated and controlled process that confers advantages during an organism's life cycle. For example, the separation of fingers and toes in a developing human [[wikipedia:Embryo|embryo]] occurs because cells between the digits undergo apoptosis. Unlike necrosis, apoptosis produces cell fragments called [[wikipedia:Extracellular_vesicle#Apoptotic_bodies|apoptotic bodies]] that [[wikipedia:Phagocyte|phagocytes]] are able to engulf and remove before the contents of the cell can spill out onto surrounding cells and cause damage to them.<ref>{{cite book|vauthors=Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P|title=Molecular Biology of the Cell (textbook)|edition=5th|publisher=[[Garland Science]]|page=1115|chapter=Chapter 18 Apoptosis: Programmed Cell Death Eliminates Unwanted Cells|year=2008|isbn=978-0-8153-4105-5|title-link=Molecular Biology of the Cell (textbook)}}</ref> | In contrast to [[wikipedia:Necrosis|necrosis]], which is a form of traumatic cell death that results from acute cellular injury, apoptosis is a highly regulated and controlled process that confers advantages during an organism's life cycle. For example, the separation of fingers and toes in a developing human [[wikipedia:Embryo|embryo]] occurs because cells between the digits undergo apoptosis. Unlike necrosis, apoptosis produces cell fragments called [[wikipedia:Extracellular_vesicle#Apoptotic_bodies|apoptotic bodies]] that [[wikipedia:Phagocyte|phagocytes]] are able to engulf and remove before the contents of the cell can spill out onto surrounding cells and cause damage to them.<ref>{{cite book|vauthors=Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P|title=Molecular Biology of the Cell (textbook)|edition=5th|publisher=[[Garland Science]]|page=1115|chapter=Chapter 18 Apoptosis: Programmed Cell Death Eliminates Unwanted Cells|year=2008|isbn=978-0-8153-4105-5|title-link=Molecular Biology of the Cell (textbook)}}</ref> | ||
Because apoptosis cannot stop once it has begun, it is a highly regulated process. Apoptosis can be initiated through one of two pathways. In the ''intrinsic pathway'' the cell kills itself because it senses [[wikipedia:Cellular_stress_response|cell stress]], while in the ''extrinsic pathway'' the cell kills itself because of signals from other cells. Weak external signals may also activate the intrinsic pathway of apoptosis. | Because apoptosis cannot stop once it has begun, it is a highly regulated process. Apoptosis can be initiated through one of two pathways. In the ''intrinsic pathway'' the cell kills itself because it senses [[wikipedia:Cellular_stress_response|cell stress]], while in the ''extrinsic pathway'' the cell kills itself because of signals from other cells. Weak external signals may also activate the intrinsic pathway of apoptosis.{{pmid|20711445}} Both pathways induce cell death by activating [[wikipedia:Caspase|caspases]], which are [[wikipedia:Protease|proteases]], or enzymes that degrade proteins. The two pathways both activate initiator caspases, which then activate executioner caspases, which then kill the cell by degrading proteins indiscriminately. | ||
In addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in a wide variety of diseases. Excessive apoptosis causes [[wikipedia:Atrophy|atrophy]], whereas an insufficient amount results in uncontrolled cell proliferation, such as [[wikipedia:Cancer|cancer]]. Some factors like [[wikipedia:Fas_receptor|Fas receptors]] and caspases promote apoptosis, while some members of the [[wikipedia:Bcl-2_family|Bcl-2 family]] of proteins inhibit apoptosis. | In addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in a wide variety of diseases. Excessive apoptosis causes [[wikipedia:Atrophy|atrophy]], whereas an insufficient amount results in uncontrolled cell proliferation, such as [[wikipedia:Cancer|cancer]]. Some factors like [[wikipedia:Fas_receptor|Fas receptors]] and caspases promote apoptosis, while some members of the [[wikipedia:Bcl-2_family|Bcl-2 family]] of proteins inhibit apoptosis.{{pmid|17562483}} | ||
== See also == | == See also == | ||