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Unformatted text preview: Concept 11.5 Apoptosis (programmed cell death) integrates multiple cell-signaling pathways. Cells that are infected or damaged, or have reached the end of their functional lifespan, often enter a program of controlled cell suicide called apoptosis . During this process, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components. The cell shrinks and becomes lobed (called “blebbing”), and the cell’s parts are packaged up in vesicles that are engulfed and digested by specialized scavenger cells. Apoptosis protects neighboring cells from the damage that would result if a dying cell leaked out all its contents, including its many digestive and other enzymes. Apoptosis plays an important role in embryonic development. The molecular mechanisms underlying apoptosis were worked out in detail by researchers studying the embryonic development of a small soil worm, a nematode called Caenorhabditis elegans. o Because the adult worm has only about a thousand cells, the entire ancestry of each cell is known. o Cell suicide occurs exactly 131 times during the normal development of C. elegans , at precisely the same points in the cell lineage of each worm.the cell lineage of each worm....
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