Cell Death

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

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

apoptosis vs necrosis