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Definition: What are the key features of apoptosis?

Apoptosis, also known as programmed cell death, is a highly regulated process that plays a crucial role in maintaining tissue homeostasis and eliminating damaged or unwanted cells. It is characterized by a series of distinct morphological and biochemical changes that ultimately lead to the controlled death of the cell.

Key Features of Apoptosis:

1. Cell Shrinkage: During apoptosis, the cell undergoes significant shrinkage due to the condensation of the cytoplasm and organelles. This shrinkage is accompanied by the compaction of the nucleus.

2. Chromatin Condensation: One of the hallmark features of apoptosis is the condensation of chromatin within the nucleus. This results in the formation of dense, irregularly shaped chromatin fragments.

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3. Nuclear Fragmentation: As apoptosis progresses, the nucleus undergoes fragmentation, leading to the formation of multiple smaller nuclear fragments called apoptotic bodies. These bodies contain condensed chromatin and are eventually engulfed by neighboring cells or phagocytes.

4. Plasma Membrane Blebbing: Another characteristic feature of apoptosis is the formation of membrane blebs on the cell surface. These blebs are small, spherical protrusions that result from the reorganization of the cytoskeleton and alterations in membrane dynamics.

5. Loss of Plasma Membrane Integrity: As apoptosis progresses, the plasma membrane of the dying cell becomes permeable, leading to the leakage of cellular contents. This loss of membrane integrity is crucial for the recognition and clearance of apoptotic cells by phagocytes.

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6. DNA Fragmentation: Apoptosis is associated with the fragmentation of genomic DNA into smaller fragments. This fragmentation is mediated by endonucleases, which cleave the DNA at specific sites, resulting in characteristic DNA ladder patterns on gel electrophoresis.

7. Activation of Caspases: Caspases are a family of proteases that play a central role in apoptosis. They are activated through a cascade of proteolytic events, leading to the cleavage of various cellular substrates and ultimately causing cell death.

8. Absence of Inflammation: Unlike necrosis, apoptosis is a non-inflammatory process. It does not elicit an immune response or release pro-inflammatory molecules, thereby preventing tissue damage and inflammation.

In summary, apoptosis is a highly regulated form of cell death characterized by distinct morphological and biochemical features, including cell shrinkage, chromatin condensation, nuclear fragmentation, plasma membrane blebbing, loss of membrane integrity, DNA fragmentation, activation of caspases, and absence of inflammation.

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Keywords: apoptosis, membrane, fragmentation, chromatin, features, shrinkage, condensation, plasma, nucleus