Apoptosis

Apoptosis is a process where cells in a multicellular organism undergo a controlled death. It is one of the main types of programmed cell death, and involves a series of cellular reactions which cause a cell to break down its internal components while maintaining its cell membrane integrity. In contrast to necrosis, apoptotic cells remain in control of their physiology and maintain their energy balance and osmotic potential. This is important because by avoiding osmotic lysis, apoptotic cells do not spill their contents into the local tissue, and so avoid initiating inflammation that can cause further damage and cell death.

Apoptosis is a normal, physiological process that cells can use to self-destruct without causing damage to any nearby cells. It can be activated by cells that have been injured or stressed before they become unable to control their metabolism, avoiding necrosis. Cells may also undergo apoptosis if they undergo changes (e.g. genetic mutations) that lead to uncontrolled or inappropriate cell division, which benefits the organism by removing cells that are functioning abnormally and which could potentially become cancerous. Apoptosis is also important in allowing cells no longer needed by the body to be removed efficiently and safely. For example, this is important for the development of digits in the embryo, where cells between digits undergo apoptosis, allowing them to become separated from each other.

Research into apoptosis is of importance in many fields of biology. In addition to its importance as an important process in growth, development and maintenance of multicellular organisms, defective apoptotic processes have been implicated in an extensive variety of diseases. For example, underactivity or loss of apoptotic pathways is one of the contributing factors to the formation of cancer, and reversing this by encouraging apoptosis in cancerous cells is one method used by some anti-cancer treatments.