apoptosis

Self-destruction of a cell. All cells contain genes that cause them to self-destruct if damaged, diseased, or as part of the regulation of cell numbers during the organism's normal development. Many cancer cells have mutations in genes controlling apoptosis, so understanding apoptosis may lead to new cancer treatments where malfunctioning cells can be instructed to destroy themselves.

During apoptosis, a cell first produces the enzymes needed for self-destruction before shrinking to a characteristic spherical shape with balloon-like bumps on its outer surface. The enzymes break down its contents into small fragments which are easily digestible by surrounding cells.

Apoptosis was thought to occur only in multicellular organisms, but three separate research groups (in Brazil, France, and the UK) found evidence 1995 that it also occurs in single-celled parasitic organisms. The evolutionary role of apoptosis has been widely accepted as the sacrifice of cells for the good of the organism as a whole, but in single-celled parasites it may be that it occurs for the good of the population; too many parasites would undermine the health of the host and jeopardize the population.

Apoptosis also occurs in some plants to prevent the spread of disease. At the start of localized infection, affected cells apoptose and isolate invading micro-organisms within a mass of dead tissue, thereby preventing them from spreading.