STD-11 UNIT-3 CHA-8
CELL : STRUCTURE AND FUNCTIONS
Functions Of Lysosomes
Intracellular Digestion- Individual cells may obtain food through phagocytosis. The same is digested with the help of lysosomes.
- For this the lysosomes release enzymes in the external environment through exocytosis.
- Lysosomes of leucocytes devour foreign proteins, toxic substances, bacteria and other microorganisms. They thus take part in natural defense of the body.
- In the metamorphosis of many animals (e.g., amphibians, tunicates) certain embryonic parts like tail, gills, etc. are digested through the agency of lysosomes. The digested food is used in the growth of other parts.
- Obstructing structures are destroyed by lysosomes.
- During periods of starvation, lysosomes provide nourishment by rapidly hydrolyzing the organic foods stored in the cells (carbohydrates, fats and proteins). Hobilization of reserve food during germination of seeds is also accomplished by lysosomes. Extra nourishment may also be got by digesting some organelles and cells.
- In long lived cells the lysosomes perform intracellular scavenging by removing old or useless organelles.
- They are lysosomal enzymes which are used for breaking limiting membrane of eggs.
- They cause breakdown of aging and dead cells.
Storage Diseases
- In certain regions due to some malfunction, the residual bodies do not undergo exocytosis. Instead, they remain inside the cells and cause disease, e.g. , hepatitis, polynephritis.
Formation of Thyroxine
- In thyroid, the active hormone thyroxine is formed through hydrolysis of thyroglobulin by the agency of lysosomes.
Cell Division
- Lysosomes seem to be essential for cell division perhaps by overcom ing agents that cause repression of mitotic cycle.
Genetic Changes
- They may harm genetic material through the release of nucleases.It may result in mutations , breakage of chromosomes and other abnormalities . Blood cancer may be result of such an activity .
- Lysosomes remove carcinogens by engulfing and separating them . However , when the carcinogen is in excess , lysosome may harm the living cells as in case of lung fibrosis caused by silicosis or asbestosis .
- Leucocyte granules are derived from lysosomes .
- At the time of formation of bones from cartilage and during remod elling of the bone , lysosomes of the osteoclasts cause breakdown of existing matrix so that it may be replaced by the new one .
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