How do cells die?

When cells are no longer needed or become injured, they commit cellular suicide or become killed by activating a specific type of programmed cell death. The three main types of programmed cell deaths include: apoptosis, autophagy, and necrosis. Apoptosis (class I cell death) is programmed cell death and is moderated by proteolytic enzymes known as caspases. The proteolytic caspase initiates cell death through cleaving proteins in the cytoplasm and nucleus. If cells are not removed, self-reactive cells may be released and attack tissues causing autoimmune disorders. Autophagy (class II cell death) is the degradation process to eliminate dysfunctional organelles and damaged proteins. Necrosis (type III cell death) and has a wide variety of cell death processes such as pyroptosis and necroptosis. Necrosis occurs when there is limited blood or oxygen flow to a tissue or cell and as a result, cells and tissues die prematurely.