All living animals and plants are made of millions of cells that have specific characters and functions.
Every cell undergoes stages of life like cell birth, multiplication, and cell death (a means to end life).
The process, namely apoptosis, and necrosis, are the two pathways by which a cell undergoes death.
This article assumes that you already know what a cell is and its organelles are. If not, take your time to go through it once before reading further.
But why should a cell undergo death while the whole animal freaks the thought of death???
The answer is to keep up the repair and homeostasis.
Repair replaces damaged cells with healthy ones for efficient function, and homeostasis keeps cell count at a fixed level.
If not, the new cells born keep on adding while old cells remain.
Then the body’s structure would have been lost, and there would be a huge mass of tissue growing everywhere.
This is what happens in cancer. The cancer cells do not die but multiply, adding to the growth of tissue.
The homeostasis is lost as the signals for cell death processes are lost.
So the cell death processes keep cell count normal, and this cell death is executed by Two processes, namely apoptosis, necrosis.
Apoptosis and necrosis are the two pathways by which a cell undergoes death and eventual destruction.
Both lead to cell death but are quite different in process, action time, and the intention for cell death.
Necrosis is an acute (sudden) unintended death process seen after most injuries or assaults. It is a fast process.
The cell destruction in this mode is quite drastic and is seen by cell swelling, rupture, or bursting (for example, you can notice this type of cell death in ulcers in the mouth) and initiates inflammation around.
Apoptosis is a normal (slow), intentional and predetermined cell death process that ends with a series of activities inside the cell before it dies and gets destroyed.
Here the cell DNA and other important material are damaged, the cell shrinks and gets detached from surrounding cells.
This cell changes its cell membrane structure (membrane blebbing; it gets consumed by macro-phages without troubling surrounding cells, unlike that of necrosis.
So apoptosis seems to be a slow yet precise mechanism of cell death.
The aim is to remove cells unfit for normal function and hemostasis.
Apoptosis & Cancer: Cancer is a condition with loss of homeostasis of cell formation and cell death.
The signals to induce apoptosis mechanism are destroyed in cancer cells. Hence, they remain alive indefinitely while other new cancer cells are formed, adding to a huge mass of tumor tissue.
This loss of mechanism to induce apoptosis leading to cell death is the key focus in cancer treatment.
The drugs used in cancer treatment are focused on causing toxicity to cancer cells by substituting the metabolites or causing other problems.
But in doing so, the other normal cells also die.
Hence there is a focus to develop drugs that can induce apoptosis by caspase activation (an apoptotic protein) in cancer cells to enable programmed cell death.
This is a repair mechanism wherein the cell accumulates all the waste or worn-out organelles into a vesicle, namely the lysosome, and destroys them.
Thus it derives energy and proteins from that degradation.
It is a cell survival phenomenon, but it sometimes gets initiated before and helps the apoptosis pathway by providing energy for complete cell destruction.
Thus sometimes autophagy appears to be involved in cell death.
Thus, apoptosis is a spontaneous cell death process, and necrosis is a cell death process mostly initiated by trauma.
Yet recent research shows necrosis to be partly programmed with non-apoptosis inducers.