Apoptosis

We all have seen trees or plants shedding their leaves, tadpole losing its tail, etc.

Why is it so? What is the factor behind this?

This is all because of the programmed cell death – Apoptosis.

The term apoptosis can be defined as a natural biological process of cell death. In this process, cells destroy itself for maintaining a smooth functioning of the body.

This is a biological process which occurs in all multicellular plants and animals. The term apoptosis is derived from the Greek word meaning dropping or falling off. It was first introduced by Kerr, Wyllie, and Currie.

Types of Cell death

There are two forms of cell death.

  1. A programmed death of cells called as Apoptosis.
  2. An uncontrolled death of cells called as Necrosis.

Apoptosis vs Necrosis

Significance of Apoptosis

  1. During the growth and development of an organism, many cells are produced in additional which finally undergoes apoptosis and thereby contributing to the formation of many organs and tissues.
  2. On an average, the human body produces two billion cells every day by the process of mitosis and some number of cells die by apoptosis.
  3. Between 50 and 60 billion cells undergo apoptosis in an average human adult and around 20 to 30 billion cells undergo programmed cell death in an average child, between the age of 7 and 15.

Why does a cell require Apoptosis?

In a normal adulthood, around 9 to 10 billion cells die every day in order to:

Maintain the balance with the new arising cells.

  1. In order to allow the different body structures to grow and develop appropriately and to remove the cells which are no more required by the body of organisms.
  2. To standardize the sizes of cell populations and cell proliferation in the adult body.
  3. To accurately control the sizes of the tissues and organs of an individual.
  4. To inhibit cells from persisting in the environment.
  5. To kill or destroy the infected cells by pathogens.
  6. To eliminate leukocytes (WBC’s) which help in producing an immune response to the body’s own cells.
  7. Apoptosis is needed for proper development and to destroy cells.
  8. For withdrawal of positive signals and to receive the negative signal.

Due to the biochemical changes in cells.

  1. Loss of electrical potential across the inner membrane of the mitochondria.
  2. During the formation of DNA fragments, genetic regulation, activation of effectors, etc.
  3. The biochemical changes, including aging, embryogenesis, and many other diseases.
  4. Changes in the plasma membrane – Getting to the Outer Leaflet of human red blood cells.
  5. Relocation of cytochrome from the intermembrane space of the mitochondria to the cytosol.

Stay tuned with BYJU’S to learn more about the apoptosis and types of cell death.


Practise This Question

In the diagram of types of placentation given below A, B, C and D respectively represent