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Apoptosis – Definition, Pathway, Significance and Roles

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  • Last Updated : 23 Jul, 2022
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A controlled sequence of cells dies through a process known as apoptosis without releasing toxic chemicals into the surrounding region. Cell suicide or planned cell death are other names for it. The most well-understood type of programmed cell death is this one. Even when a cell is killed, the organism gains from it. The cell’s contents are systematically packed into little membrane packets for the immune cells to gather waste. Removing cells that are in the process of developing, as well as possibly malignant and virus-infected cells, aids in maintaining the body’s equilibrium.

The process is known as apoptosis when a cell “decides” to die on purpose in a multicellular organism. This frequently happens for the benefit of the entire organism, for example, when a cell’s DNA has been broken and it may become cancer.

  • Apoptosis is the name for cell death that is planned.
  • Necrosis is the name for an uncontrolled death of cells.

Mechanism of both Intrinsic and Extrinsic Pathways

There are two main categories of apoptosis pathways:

Intrinsic Pathway: The mitochondrial pathway is another term for this process. When DNA damage is detected, one of the cell’s own genes or proteins sends a signal to the cell to kill itself. This process is also called the mitochondrial pathway.

Extrinsic Pathway: In this case, other cells in the body provide a signal to a cell to begin apoptosis. When a cell has reached the end of its functional life or is no longer a wise investment for the organism to sustain, this occurs. This is also called the death receptor pathway.

Apoptosis Steps

  • The decrease of cell volume is a common feature of programmed cell death, and Cell Shrink is seen in all forms of apoptosis.
  • The DNA in the cell’s nucleus condenses and fragments into pieces of uniform size in the Cell Fragments step.
  • Cytoskeleton Collapses – At this point, the cytoskeleton of the young organism collapses.
  • Disassembling the Nuclear Envelope: This stage involves disassembling the nuclear envelope.
  • In the stage of Cells Release of Apoptotic bodies, cells go through morphological changes that include membrane damage, the creation of thin membrane protrusions, and the production of discrete apoptotic bodies 

Function of Apoptosis

Apoptosis provides the following functions for the organism and is essential for planning.

  • Rebuild some defective and older cells with fresh ones that do the same function, maintaining the health of the body. This is crucial in the case of the body’s defense cells, which may acquire a tendency to wrongly target healthy areas.
  • Getting elimination of atypical cells that have small, abnormal, virus- or DNA-damaged, or atypical characteristics during birth.
  • Participate in the early development of the organism during critical moments, such as the embryonic stage, when tissue must be shed or divided. For instance, a membrane holds the fingers together as they develop.
  • The membrane’s cells need to be set up to die in order to separate the fingers. During menstruation, the uterine endometrium experiences the same thing.

Significance of Apoptosis

  • Apoptosis causes about one lakh cells in the human body to die every single second, while mitosis results in a comparable number of new cells.
  • Cell development depends on programmed cell death.
  • In typical youngsters between the ages of 8 and 14, between 29 and 30 billion cells each day perish.
  • Our bodies undergo a full epithelial lining change called apoptosis every 23 days.
  • Apoptosis eliminates the harmful T-lymphocytes.
  • Apoptosis keeps the number of cells in an organism constant.
  • Apoptosis causes undesirable cells to die and leave the body.
  • This results in the overproduction of cells that eventually experience programmed cell death, shaping various organs and tissues throughout development.

Difference between Apoptosis and Necrosis

Apoptosis

Necrosis

Apoptosis is a common process of cell death in the body where the cell participates in its own demise. Necrosis is a type of cellular death that takes place when cells are subjected to extremely severe external circumstances.
It is a natural process and not the result of outside causes. It is brought on by outside factors including poisons, injuries, and infections.
The membrane of the cell breaks into many apoptotic bodies. The cell membrane ruptures, releasing the cellular components.
Shrinkage of cells occurs in this Apoptosis. Swelling of cells occurs in this Necrosis.
It is a pre-planned cell death pathway It is not a pre-planned cell death pathway
The cells in this do not require any treatment. The cells are not natural and need treatment

Apoptosis Examples

Mouse Feet – During embryonic development, mice’s feet begin as flat, spade-shaped structures. The feet divide into five unique toes through the process of apoptosis as growth progresses. The cells link with one another to form discrete gaps between them.

From Tadpole to Frog Evolution – The most remarkable and best example of apoptosis is seen in frog tadpoles, which completely destroyed and reabsorb their bodily components as they develop into frogs. As the tadpole ages, the cells of its gills, fins, and tail tend to die via apoptosis signals. The raw material of the damaged cells becomes an important substance and also supplements as food for new developing limbs.

Frequently Asked Questions

Question 1: Write about Apoptosis?

Answer:  

A controlled sequence of cells dies through a process known as apoptosis without releasing toxic chemicals into the surrounding region. Cell suicide or planned cell death are other names for it. The most well-understood type of programmed cell death is this one. Even when a cell is killed, the organism gains from it. The cell’s contents are systematically packed into little membrane packets for the immune cells to gather waste. Removing cells that are in the process of developing, as well as possibly malignant and virus-infected cells, aids in maintaining the body’s equilibrium.

Question 2: Write an example for Apoptosis?

Answer: 

From Tadpole to Frog Evolution – The most remarkable and best example of apoptosis is seen in frog tadpoles, which completely destroyed and reabsorb their bodily components as they develop into frogs. As the tadpole ages, the cells of its gills, fins, and tail tend to die via apoptosis signals. The raw material of the damaged cells becomes an important substance and also supplements as food for new developing limbs.

Question 3: What is an Intrinsic Pathway?

Answer: 

Intrinsic Pathway: The mitochondrial pathway is another term for this process. When DNA damage is detected, one of the cell’s own genes or proteins sends a signal to the cell to kill itself. This process is also called the mitochondrial pathway.

Question 4: Write steps for Apoptosis?

Answer: 

  1. The decrease of cell volume is a common feature of programmed cell death, and Cell Shrink is seen in all forms of apoptosis.
  2. The DNA in the cell’s nucleus condenses and fragments into pieces of uniform size in the Cell Fragments step.
  3. Cytoskeleton Collapses – At this point, the cytoskeleton of the young organism collapses.
  4. Disassembling the Nuclear Envelope: This stage involves disassembling the nuclear envelope.
  5. In the stage of Cells Release of Apoptotic bodies, cells go through morphological changes that include membrane damage, the creation of thin membrane protrusions, and the production of discrete apoptotic bodies 

Question 5: What are the functions of Apoptosis?

Answer:

Apoptosis provides the following functions for the organism and is essential for planning.

  1. Rebuild some defective and older cells with fresh ones that do the same function, maintaining the health of the body. This is crucial in the case of the body’s defense cells, which may acquire a tendency to wrongly target healthy areas.
  2. Getting elimination of atypical cells that have small, abnormal, virus- or DNA-damaged, or atypical characteristics during birth.
  3. Participate in the early development of the organism during critical moments, such as the embryonic stage, when tissue must be shed or divided. For instance, a membrane holds the fingers together as they develop. 
  4. The membrane’s cells need to be set up to die in order to separate the fingers. During menstruation, the uterine endometrium experiences the same thing.

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