programmed cell death .pptx

1. Brief introduction and history about PROGRAMMED CELL DEATH or APOPTOSIS
2. Types of apoptosis
3. Pathways of apoptosis

1. PRESENTED BY D. JASMINE PRIYA, B.Sc., DCA., M.Sc., PGDCLT. DR. NGP ARTS AND SCIENCE COLLEGE COIMBATORE PROGRAMMED CELL DEATH (APOPTOSIS)

2. What is programmed cell death ? Programmed cell death(PCD) involves a series of biochemical events leading to a characteristic cell morphology and death, in more specific terms, a series of biochemical events that lead to a variety of morphological change include Blebbing , changes to the membrane such as loss of membrane asymmetry and attachment and chromosomal DNA fragmentation. Other name for PCD – Apoptosis “The term apoptosis can be defined as a natural biological process of programmed cell death in which the cells destroy themselves for maintaining the smooth functioning of the body.”

3. The term apoptosis is derived from the Greek word meaning dropping or falling off. Apoptosis is a biological process which occurs in all multicellular organisms including plants and animals. It removes the cells from the organisms that should no longer be a part of the organism.  This process plays a major role in the development of humans and in developing and maintaining a healthy immune system. On an average,  50 – 80 billion cells die every day in a human adult due to apoptosis. During this biological process, infected cells, pre-cancerous cells and other cancer cells are eliminated successfully and maintain the balance of cells in the human body. Therefore, it is an essential process that is responsible for the normal development of cells,  cell cycle maturation and maintaining the regular functions and activities of cells.

4. HISTORY The concept of PCD was used by Lock shin and Williams in 1964 in relation to insect tissue development, around 8 years before “apoptosis” was coined. Since then, PCD has become the more general of these two terms. PCD has been the subject of increasing attention and research efforts. This trend has been high lighted with the award of the 2002 Nobel prize in physiology or medicine to Sydney Brenner , H.R. Horvitz and J.E. Sulston.

5. TYPES OF PCD There are two forms of cell death have been reported Apoptosis (type I cell death) Autophagic (type II cell death) Besides these two types of PCD, other pathway have been discovered. Called non- apoptopic PCD or caspase-inde pendent PCD or necrosis-like PCD. These alternative routes to death are as efficient as apoptosis and can function as either backup mechanism or the main type of PCD. Other forms of PCD include Anoikis , almost identical to apoptosis except in its induction; comfication , a form of cell death exclusive to the eyes; excitotoxicity and Wallerian degeneration plant cells undergo particular processes of PCD which are similar to autophagic cell death. However some features of PCD are highly conserved in both plants and metazoa . Both apoptosis and necrosis occur under different circumstances and involve different steps .

6. APOPTOSIS PATHWAYS The process of apoptosis undergoes two pathways: Extrinsic Pathway Intrinsic Pathway 1. Extrinsic Pathway This pathway triggers apoptosis in response to external stimuli, like, ligand binding at death receptors on the cell surface. These receptors are members of the Tumor Necrosis Factor gene family. The receptor binding initiates caspase 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 whether a  cell  will survive or undergo apoptosis in response to the stimuli.

7. Difference between intrinsic and extrinsic pathway

8. SIGNIFICANCE OF APOPTOSIS Apoptosis is significant for the following reasons: It helps to maintain homeostasis in the multicellular organisms. Proper size of the body is maintained by apoptosis. Apoptosis maintains the constancy of cell number in an organism. The unwanted cells are eliminated from the body by apoptosis. The dangerous T-lymphocytes are eliminated by apoptosis. Programmed cell death is crucial for cell development.

9. ROLE OF APOPTOSIS Apoptosis plays an important role in the body of an organism. Following are a few such roles performed by the process: The separation of the fingers during the development of the foetus is due to apoptosis. It results in the closure of the neural tube in the dorsal part. Programmed cell death results in the removal of vestigial remnants such as pronephros. During the determination of sex of the foetus , the Wolffian ducts are removed by cell death. In the urachus, apoptosis allows the removal of redundant tissues between the bladder and umbilicus.