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In multicellular organisms, the cells go through a number of different stages of development and death. Cellular death is very important for any organism's survival and growth in order to live and thrive. Our bodies are made up of a variety of distinct types of cells that are distributed throughout the body.
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There are two methods in which a cell may die and each of these techniques are equally effective. There are numerous ways in which this may happen: via exposure to an inappropriate or hazardous environment, through an accident, or through a carefully controlled disintegration process. Apoptosis and necrosis are two distinct types of cell death that occur under various circumstances.
Cell Death
Cell death may be caused by a variety of harmful substances or even physical events such as radiation, trauma, heat, or a loss of oxygen supply owing to a decrease in blood flow. All of these chemical or physical processes have the potential to cause a fatal disturbance of both the structure and function of the cell.
Types of Cell Death
Apoptosis and necrosis are two different types of cell death that vary substantially in all respects except the last stage of the process. Necrosis is defined as a type of cell death in which the cell dies in an untimely manner as a result of certain uncontrolled environmental circumstances. Apoptosis is referred to be a planned suicide cell, in which the cell kills itself in order to preserve the proper functioning of the body.
Apoptosis Definition
Apoptosis is a kind of cell death that is planned and controlled. But what exactly is apoptosis? Apoptosis, or programmed cell death, is the most frequent kind of cell death. A variety of physical, chemical, and biological stimuli may cause it to activate, and the cellular reaction that occurs as a result is very carefully controlled. CASPASES are a family of proteases that are active during the process of apoptosis and are responsible for the controlled destruction of cellular components that happens throughout the process.
Apoptosis
It is a highly regulated and managed process that provides advantages to an organism at various stages of its life cycle. It starts when the nucleus of the cell begins to shrink, and it continues until the cell dies. Following the shrinkage, the plasma membrane blebs and folds around the various organelles in the cell. The blebs continue to develop, and the organelles break and disperse as they move further apart from one another.
It is possible to start apoptosis by one of two pathways:
- Intrinsic route (also known as intrinsic pathway)
- Intrinsic route vs. extrinsic pathway
Caspases
Caspases exist as proenzymes in their dormant forms in the bodies of healthy cells. Apoptotic signalling causes the activation of the caspase cascade (caspase -2,-8, -9, and -10, called initiator caspases). Following that, downstream effector caspases are cleaved and activated by the initiator caspases in turn (caspase -3, -6, and -7). Effector caspases are responsible for the execution of apoptosis by cleaving certain cellular proteins. It is possible for apoptosis to be triggered by internal stimuli (such as DNA damage, ER stress, elevated ROS levels, or cell abnormalities during mitosis) or external stimuli (such as extracellular stimuli that are recognised by cells via plasma membrane receptors).
Definition of Necrosis
The term "necrosis" refers to uncontrolled cell death. What exactly is necrosis? Necrosis is a kind of cell damage that is described as uncontrolled cell death caused by internal or external stressors such as mechanical traumas, chemical agents, or infections. It is typically a quick process that results in cell swelling (oncosis) and bursting as a result of a decrease in osmotic pressure.
Necrosis
The term "necrosis" refers to the death of bodily tissue. It occurs when just a small amount of blood is delivered to the tissue. This can occur as a result of an injury, radiation, or chemical exposure. There is no way to reverse necrosis. It is possible to develop necrosis following a wide range of traumas, both physical and biological in nature. Cuts, burns, bruising, and hyperthermia are just a few of the physical ailments that might occur. An immunological attack as well as the impacts of disease-causing substances are examples of biological damage that can occur.
Difference Between Apoptosis and Necrosis
| Apoptosis | Necrosis |
|---|---|
| Apoptosis is a normal process of cell death that happens in the body, in which the cell itself participates in the death. | Necrosis is a biological process of death that occurs when cells are subjected to severe external circumstances. |
| It is a natural process that is not influenced by outside forces. | External factors such as illness, trauma, and poisons cause it. |
| Even after the cell dies, the organelles continue to operate. | After a cell dies, the organelles cease to function. |
| The cell membrane shatters into a number of apoptotic entities. | The cell membrane ruptures, allowing the contents of the cell to be released. |
| This procedure is believed to be rather helpful. However, it is considered abnormal if the cellular mechanisms that maintain the body balanced produce too many or too few cell deaths. | It is usually detrimental or destructive. |
| During the apoptosis process, no symptoms are noticed. | During the process, symptoms such as inflammation, tissue loss, and reduced blood flow at the infected location are noted. |
| It is caused by self-generated impulses within the cell. | Bacterial and fungal infections, mycobacterial infections, denatured proteins, pancreatitis, or antibody and antigen deposits are all causes. |
| Apoptosis does not need extensive therapy. | When left untreated, necrosis is believed to be extremely hazardous and can be deadly. As a result, medical care is critical in cases of necrosis. |
| Because enzymes carry out the action, there is no need for energy. | This procedure necessitates the use of energy in order to be carried out. |
Things to Remember
- Cellular death is very important for any organism's survival and growth in order to live and thrive.
- Apoptosis and necrosis are two different types of cell death that vary substantially in all respects except the last stage of the process.
- Apoptosis is a kind of cell death that is planned and controlled.
- Necrosis is a kind of cell damage that is described as uncontrolled cell death caused by internal or external stressors.
- Effector caspases are responsible for the execution of apoptosis by cleaving certain cellular proteins.
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Sample Questions
Ques. Define Apoptosis(2 Marks)
Ans. Apoptosis, or programmed cell death, is the most frequent kind of cell death. A variety of physical, chemical, and biological stimuli may cause it to activate, and the cellular reaction that occurs as a result is very carefully controlled.
Ques. Define Necrosis (2 Marks)
Ans. Necrosis is a kind of cell damage that is described as uncontrolled cell death caused by internal or external stressors such as mechanical traumas, chemical agents, or infections. It is typically a quick process that results in cell swelling (oncosis) and bursting as a result of a decrease in osmotic pressure.
Ques. When might a cell go through the process of apoptosis?(2 Marks)
Ans. Apoptosis is a process in which cells that are no longer required or that pose a hazard to the system are killed through a strictly regulated cell suicide mechanism.
The following is what occurs if the necrotic tissue is not removed.
Wounds that have necrotic tissue present will not heal, according to the answer. If you remove the necrotic tissue from a wound, the bacterial bioburden of the lesion will decrease, which will allow healthy tissue to develop in its stead.
Ques. What is the best way to identify the difference between apoptosis and necrosis in an experimental setting?(2 Marks)
Ans. If apoptosis is the cause of the cell death, you will notice the growth of AnnexinV alone stained cells first, followed by the arrival of double stained Annexin/PI cells. If you only observe cells that are doubly stained, it is probable that you are dealing with necrosis. Either a caspase 3 specific FLICA reagent or an antibody may be used to confirm the presence of apoptosis.
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