Apoptosis TDC PART lH DR BABITA BARDHAN ASSISTANT
Apoptosis TDC PART - l(H) DR. BABITA BARDHAN ASSISTANT PROFESSOR DEPARTMENT OF BOTANY JPM COLLEGE, CHAPRA
Apoptosis (Programmed Cell Death) Apoptosis is a naturally occurring process by which a cell is directed to programmed cell death. The name Apoptosis is a Greak name describing falling of leaves. Apoptosis or programmed cell death, is a highly regulated process that allows a cell to self – degrade in order for the body to eliminate unwanted or dis functional cells. During apoptosis, the genome of the cell will fracture, the cell will shrink and part of the cell will disintegrate in to smaller apoptotic bodies.
Characteristic of Apoptotic cell death A apoptotic cell death is characterised by : — Ø Shrink of the cell Ø Shrinkage of the nucleus Ø Loss of adhesion to the neighbouring cells Ø Formation of membrane blebs (externalisation of inner leaflet of membrane Ø Decay of m. RNA
Characteristic of Apoptotic cell death Condensation of fragmentation of chromatin (DNA) Formation of small fragmented chromatin in membrane bounded structure called antipodal bodies Rapid engulfment of the apoptotic cell debris by the process of phagocytosis
Apoptosis Pathway The process of apoptosis undergoes two pathways 1. Extrinsic Pathway 2. Intrinsic Pathways
1. Extrinsic Pathway The pathway triggers apoptosis in response to external stimuli, like, ligand binding at death receptors on the cell surface. These receptors are members of the Tumour Nacrosis Factor gene family. The receptor binding initiates activation.
2. Intrinsic Pathway This pathway triggers apoptosis in response to internal stimuli such as biochemical stress. DNA damage and lack of growth factors. This pathway is modulated by two groups of molecules – Bax and Bcl-2. These groups of molecules determine weather a cell will survive or undergo apoptosis in response to the stimuli.
Significance of Apoptosis is significant for the following reasons 1. It helps to maintain homeostasis in the multicellular organisms. 2. Proper size of the body is maintenance by apoptosis. 3. It maintains the constancy of cell number in an organism. 4. The unwanted cells are eliminated from the body by apoptosis. 5. The dangerous T-lymphocytes are eliminated by apoptosis. 6. Programmed cell death is crucial for cell development.
Role of Apoptosis plays an important role in the body of an organism. Following are a few such roles performed by the process. 1. The separation of the fingers during the development of the foetus is due to apoptosis. 2. It results in the closer of the neutral tube in the dorsal part. 3. Programmed cell death results in the removal of vestigial remnants such as pronephros. 4. During the determination of sex of the foetus, the Wolffian ducts are removed by cell death. 5. In the urachus, apoptosis allow the removal of redundant tissues between the bladder and umbilicus.
Relationship between Apoptosis & Cancer is the uncontrolled division of the cells that leads to the development of tumour. If the apoptotic signalling works properly, these unwanted cells can be removed from the body. The main reason for cancer is that they have the ability to prevent apoptosis and therefore multiply uncontrollably.
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