Programmed cell death such as apoptosis, autophagy, and necrosis, describes the death of a cell through a highly regulated process, and serves many functions in an organism.

Programmed cell death (or PCD) is the death of a cell in any form, mediated by an intracellular program. PCD is carried out in a regulated process, which usually confers advantage during an organism’s life-cycle. Apoptosis and autophagy are both forms of PCD, but necrosis is a non-physiological process that occurs as a result of infection or injury and could confer damage to nearby cells.

Apoptosis is the process of PCD that may occur in multicellular organisms. It may lead to morphological cell changes and death. It is essential for normal embryological development. For instance, early stages of development include the formation of web-like tissue between individual fingers and toes in vertebrates. During normal development, unneeded cells are eliminated through apoptosis to enable the formation of fully separated fingers and toes. 

Autophagy is a type of programmed cell death accomplished through self-digestion. It is characterized as a catabolic process via the formation of an autophagolysosome which degrades damaged cellular contents. It has been associated with development, differentiation, neurodegenerative diseases, stress (physiology), infection and cancer. 

Necrosis is the death of a cell caused by external factors such as trauma or infection and occurs in several different forms. Programmed necrosis, called necroptosis, can serve as a cell-death backup to apoptosis.

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Key Points

• Programmed cell death can provide an advantage to an organism during development, for instance, by maintaining homeostasis and protection against potentially disruptive issues that may arise during the life of a cell.

• Apoptosis is a process of programmed cell death that is regulated by numerous biochemical events and appears to be genetically mediated.

• Autophagy is a process of programmed cell death that is characterized as a catabolic process via the formation of an autophagolysosome which degrades damaged cellular contents.

• Necrosis occurs when cellular death is caused by external factors and is characterized as an alternate form of programmed cell death, called necroptosis.

Key Terms

apoptosis: a process of programmed cell death

extracellular matrix: All the connective tissues and fibers that are not part of a cell, but rather provide support.

autophagy: a type of programmed cell death accomplished through self-digestion