Apoptosis Definition, Pathway, Significance, and Role

What is Apoptosis?

Have you ever seen the feet of a duck? There is the skin between the toes since they are webbed. Did you also know that the webs on your fingers and toes were present before you were born? Your fingers did indeed resemble the webbed feet of a duck. So why they are not any more webbed?

You may wear rings on your fingers and move each toe independently because of apoptosis. Cell suicide or programmable cell death is known as apoptosis. It may sound fairly gloomy, yet survival depends on it. Why? Many things, including your organs, are kept in the proper size, shape, location, and functionality thanks in part to apoptosis. There are various ways to pronounce this word. While some pronounce it "a-pop-toe-sis," others insist on "ape-o-toe-sis," with a second silent "p." You now understand that apoptosis is a type of planned cell death. There are primarily two types of cell death, which you should be aware of.

  • When a cell is injured, it doesn't go through apoptosis; instead, it goes through necrosis, a different sort of cell death that involves inflammation, releases toxins to nearby cells and frequently leads to more problems

  • A cell going through apoptosis, however, does not experience these side effects. Instead, everything is contained within the plasma membrane, which acts as the cell's exterior boundary

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One way to identify an apoptotic cell is by−

  • chromatin condensation

  • Blebbing membrane (or formation of irregular bulges)

  • reduced cell size

  • nuclear envelope disintegration

The cell will be destroyed by being eaten by a macrophage or an adjacent cell. Yes, the apoptotic cell gets cannibalized and its components are recycled; while this may be a little upsetting, keep in mind that it is an essential element of how we survive.

Apoptosis pathways

Extrinsic and intrinsic apoptotic pathways are two important signalling mechanisms leading to apoptosis of cells

  • The extracellular environment initiates the extrinsic pathway of apoptosis. It starts outside of a cell.

  • When a cell sustains damage, the intrinsic mechanism of apoptosis starts when the stress brought on by the lesion initiates the apoptotic pathway

The activation of Cysteine proteases or caspases lead to the activation of proteolytic cascade. This eliminates the dying cell through extrinsic and intrinsic pathways.

Apoptosis pathways come in two different varieties

  • Extrinsic Pathway− Alternative word for this is the death receptor pathway. A signal from outside the cell instructs it to carry out programmed cell death via the "extrinsic" pathway to apoptosis. This might happen if the cell is sick or no longer required. The extrinsic road to apoptosis has numerous phases, each of which can be "upregulated" or "downregulated" due to gene expression or by other molecules, similar to many processes for bringing about complicated changes in a cell

  • Intrinsic Pathway− The intrinsic pathway is another name for the mitochondrial pathway. When DNA damage is detected, one of the cell's genes or proteins sends the signal for the cell to die. For instance, chemotherapy and/or radiotherapy may start the intrinsic apoptosis process. It is triggered by a variety of external and internal stressors, including oxidative stress, ischemia, and DNA damage. Additionally, it is crucial for cell formation and removal of damaged cells. One interesting target for novel treatments is the intrinsic mitochondrial pathway of apoptosis, and effective targeting of this system has the potential to change the therapeutic environment for a range of malignancies

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Steps of Apoptosis

  • Cell Shrinks − The decrease in cell volume is a recurrent feature of programmed cell death, as seen in all forms of apoptosis.

  • Cell Fragments − In this stage, the DNA in the cell's nucleus condenses and fragments into pieces of uniform size.

  • Cytoskeleton Collapses − The cytoskeleton of the developing organism collapses at this point..

  • Nuclear Envelope disassembles − The nuclear shield is now disassembled

  • Cells go through morphological changes at this stage, including the creation of discrete apoptotic bodies, thin membrane protrusions, and membrane blebbing

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Significance of Apoptosis

The following are some reasons why apoptosis is important−

  • In multicellular organisms, it aids in preserving homeostasis.

  • Apoptosis keeps the body's size in check.

  • The process of apoptosis keeps an organism's cell count constant

  • Apoptosis allows the body to rid itself of undesirable cells.

  • Apoptosis gets rid of the harmful T-lymphocytes.

  • Cell development depends on programmed cell death.

Role of Apoptosis

Apoptosis is a crucial process in an organism's body. The process plays the following roles, to name a few−

  • Apoptosis is what causes the fingers to separate when the fetus is developing

  • The dorsal section of the neural tube closes as a result.

  • Vestigial remains, like pronephros, are eliminated as a result of programmed cell death

  • The Wolffian ducts are eliminated through cell death during the fetal sex determination process.

  • Apoptosis in the urachus enables the elimination of extraneous tissues in the region between the bladder and umbilicus

Relationship between Apoptosis and Cancer

Carcinogenesis is another name for cancer. A normal cell turns into a malignant one as a result of a series of genetic alterations, and one of the necessary modifications in a cell that results in this malignant transformation is the avoidance of cell death. Similar to apoptosis, a huge number of cells perish, lowering an individual's risk of developing cancer. When a cancer patient's body experiences apoptosis, a diagnosis can be made without any risk factors. These undesirable cells can be eliminated from the body if the apoptotic signaling process is effective. The primary cause of cancer is the capacity of these cells to stop apoptosis, which causes them to proliferate uncontrollably


Q1. Give an illustration of apoptosis?

Ans. The human nervous system− A significant portion (almost 50%) of cells are eliminated through apoptosis during the early development of the nervous system in the human embryo. There is some uncertainty regarding the precise cause of the loss of so many neurons. However, it has been postulated that a greater number of cells are formed to guarantee the effectiveness of the process because the neurons have a propensity to make complicated connections. This causes the production of more neurons, which are later eliminated to maintain the number of neurons in the nervous system

Q2. What elements influence apoptosis?

Ans. The kind of stimulus and/or the intensity of the stimulus can sometimes dictate whether cells die by apoptosis or necrosis. Numerous adverse stimuli, including heat, radiation, and hypoxia, and cytotoxic anticancer drugs, can produce necrosis when present in high concentrations, but they can also activate apoptosis in moderate quantities.

Q3. Apoptosis serves what purpose?

Ans. Apoptosis has candidate cells that have mutations that could be detrimental. Failure of the apoptotic mechanism will cause the cell to grow and divide uncontrollably, eventually resulting in the formation of a tumor.

Q4. Depending on which component is present on the surface, apoptotic bodies can be identified?

Ans. The phosphatidylserine on the surface of the apoptotic bodies makes them easy to spot. A substance called phosphatidylserine is typically found on the plasma membrane's inner surface

Q5. A cell that has been injected with Bcl-2 will go through apoptosis or not?

Ans. Anti-apoptotic protein is Bcl-2. Apoptosis is maintained by a healthy balance of pro-and anti-apoptotic proteins. In this situation, apoptosis will not occur.


Simply Easy Learning

Updated on: 13-Oct-2022


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