Apoptosis Definition

What is apoptosis? Apoptosis is the process of programmed cell death.

Preventing apoptosis

Apoptosis is important in embryonic development, in the immune system and in all living tissues. In embryonic development creates apoptosis sure not disappear necessary or unwanted tissues. An example is the "interdigital webs," the "flippers", which are present in human construction, but disappear during the development of the embryo. In the immune system are T-cells that "own" recognize epitopes and thus are undesirable, to cell death induced by stimulation of apoptosis.

A cell may die in two ways. Apoptosis, as discussed herein, or necrosis; this is the process by which a cell in an abrupt way to die. Here, the contents of the cell, the cytoplasm, released into the surrounding tissue. This often has an activating effect on the immune system, and this can cause an inflammatory reaction.

The biochemical mechanism responsible for apoptosis

A cell for a more organized way of death is apoptosis. Apoptosis-programmed cell death is called, because the mechanisms are present in each cell, which allow apoptosis. If a cell receives signals from its surroundings, which force the cell to apoptosis, or if the cell has risen so much damage that further consist is not possible, an intracellular mechanism is activated. This mechanism ultimately leads to the activation of proteases, called caspases (cysteine-aspartyl). These proteins turn the cell on to the degradation of proteins and DNA. The substrates of caspases are located in the cell nucleus, the cytoplasm, and the cytoskeleton.

The basis of the programmed cell death in mammals has been divided into three groups of proteins, all belonging to the Bcl-2 superfamily:
  • Sensors: Inhibit the protectors. When an adequate concentration of sensors are blocked protectors which the effectors to be active.
  • The Guardians: Inhibiting the action of the effectors and thereby avoid apoptosis.
  • The effectors: Putting the apoptosis cascade in motion by making the mitochondrial membrane permeable to cytochrome c.

That there are multiple proteins within a group fall resulting in redundancy of the system, wherein upon the occurrence of non-functional proteins, other proteins, the system can keep operating.

The increased concentration of cytochrome c in the cytoplasm then leads to activation of the apoptosome. The apoptosome is responsible for the activation of caspase-9, which in turn activates caspase-3. The conversion of pro-caspase-3 to caspase-3 marks the selesai death of the cell in question. Caspase-3 is responsible among other things for cleaving proteins that maintain the homeostasis of the cell, promotes the degradation of the cytoskeleton and activates endonucleases.

Characteristics of apoptosis

A cell undergoing apoptosis can be identified by a number of characteristics. The most obvious morphological characteristic is the splitting off of small globules cytoplasm with cell contents (blebbing). Also apoptotic cells can be identified by DNA fragmentation as a result of degradation of the DNA. Cells undergoing apoptosis also display negatively charged phospholipids on the cell surface. These negatively charged phospholipids can be recognized by phagocytes. After recognizing the phagocyte removes the apoptotic cell.

 Apoptosis is the process of programmed cell death Apoptosis Definition

Apoptosis and Cancer

In some forms of cancer can be several systems that monitor the integrity of the cell are switched off. These cells will then not be able to proceed to apoptosis, which may lead to a too large amount of cells, or by growing cells which are actually too severely damaged to grow through.

Modern pharmacological research is aimed to develop new compounds which in turn can activate the apoptosis pathway. This includes, for example, navitoclax that inhibits the action of Bcl-2 (by binding to its BH3 domain), which has the role of protector in the programmed cell death. Blocking the function of the protector ensures that effectors able to make active the mitochondrial membrane permeable, eventually causing caspase-3 can be activated again.

Apoptosis in plants

Apoptosis in plants is a natural reaction that occurs frequently. As apoptosis when wilting flowers and ripening of some fruits such as fruit box.

Also occurs in the event of damage to plants. Plants by trying to maintain a balance between the amount of aboveground and underground parts. Above-ground parts are removed by, for example, feeding nutrients then be extracted from parts of the root system, wherein roots die. When transplanting above-ground parts will be discarded, and in fluid deficiency will also die above-ground parts in order to enable the plant to survive.

In attack by pathogens occurs sometimes apoptosis in and around the infected cells, preventing further infection is prevented. This is reflected in resistance to the pathogen.

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