The death of a cell may occur by one of two main mechanisms – necrosis or apoptosis
While necrosis is a traumatic cellular response that is detrimental, apoptosis is an important and necessary cellular process
Necrosis is uncontrolled cell death (‘cell homicide’)
- Necrosis is the premature death of a cell, caused by disruption to the cell by injury, toxins or nutritional deprivation
- The cell loses functional control and there is destabilisation of the plasma and organelle membranes
- This leads to swelling of the cell and organelles due to increased osmotic pressure, and the cell eventually bursts
- The uncontrolled release of cell contents causes inflammation, potentially damaging surrounding tissue
Apoptosis is programmed cell death (‘cell suicide’)
- Apoptosis is a controlled event regulated by molecular signals which inhibit or promote this process
- Mitochondrial proteins play an important role in initiating apoptotic processes
- Catabolic reactions are triggered which digest cytoplasmic components, including the cytoskeleton
- The plasma membrane undergoes irregular bulging, or blebbing, and cell contents are repackaged for safe removal
- The cell shrinks and fragments into apoptotic bodies which are subsequently engulfed by neighbouring cells
Mechanisms of Cell Death
Apoptosis versus Necrosis
Apoptosis and necrosis can be distinguished according to a number of differential features – these include:
- Size (cellular response and area of effect)
- Uptake (destination of contents and localised effects)
- Membrane (integrity of bilayer)
- Organelles (preserved or destroyed)
Mnemonic: SUMO
Differential Comparison of Mechanisms of Cell Death
