Apoptosis, what is it all about?

• It is known as programmed cell death _[2]
• It aims to remove cells that are no longer functionally important _[3]
• A target cell is acquired and it removes this cell neatly without inflammation
• No inflammation is important as it could damage surrounding cells
• If apoptosis goes wrong it could result in disease e.g. cancer or AIDS (Acquired Immunodeficiency Syndrome)
• It is totally different to necrosis in the way the processes function
• FUN FACT: 50,000 of the cells in your body will die and be replaced with new cells while you read this sentence.
   

Apoptosis VS Necrosis!

 

Apoptosis	Necrosis
Neat	Messy
Planned physiological process to remove cells	Death of cells that cannot survive due to ATP depletion
Disassembly into membrane enclosed vesicles	Cell membrane breaks and the cytosol exits the cell
No inflammation and phagocytosis by macrophages	Inflammation
Chromatin condensation	Vacuolation (formation of a vacuole in the cell)
Leads to cell death	Leads to cell death

The above table is just an overview of the differences and similarities between apoptosis and necrosis _[4]. This relationship will be explained further.

The image clearly depicts the differences between the stages of each process with necrosis on the left and apoptosis on the right [5].

A few details

• There are two pathways that are interlinked, which activate apoptosis _[6]
• The internal pathway results from caspase activation by mediators released from the mitochondria
• The external pathway is where a death receptor attaches itself to the surface of a cell
• symptoms of apoptosis include
  • nuclear condensation _[4]
  • fragmentation of DNA of around 200 base pairs long _[4]
  • disassembly into membrane enclosed vesicles prepared for phagocytosis _[4]
• Symptoms of necrosis include:
  • Vacuolation of the cytoplasm _[4]
  • inflammation around the dying cell _[4]
  • plasma membrane disintegration causing the contents to 'leak' out _[4]
• Apoptosis is a planned physiological process that is organised for the benefit of the cell _[2]
• Necrosis is an accidental death of a cell due to depletion of ATP and other factors which mean it can no longer survive._[4]