The digestive enzymes in a cell are stored in the weegy,best probiotics crohn's disease 8th,best probiotics for breastfeeding moms tumblr - Step 2

By 1949 a class of particles having centrifugal properties somewhat intermediate between those of mitochondria and microsomes was isolated by de Duve and found to have a high content of acid phosphatase and other hydrolytic enzymes. Lysis = dissolution, soma=body).According to Cohan (1972) membrane bounded storage granules containing digestive enzymes are considered lysosomes of plants. The presence of lysosomal particles have also been suspected (and in some cases established) in protista (protozoan, slime-moulds, fungi, algae and prokaryotic protista). In plant cells, considering the evidences as a whole, there now seems little doubt about their presence.Further, they have strong affinities with the lysosomes of animals and protista (Pitt and Galpin 1973). According to Pitt lysosomes and spherosomes are two different organelles and the latter are comparable to lipid droplets of animal. Yatsu and Jack (1972) have clearly shown that spherosomes are morphologically distinct organelles. Due to their changing habit they cannot be accurately identified as the basis of the shape. Limiting membrane: This membrane is single, unlike that of mitochondria and composed of lipoprotein.
The chemical structure is homologous with the unit membrane of plasma lemma consisting of bimolecular layer as suggested by Robertson.2.
Certain substances called labializes, cause instability of the lysosomal membrane, leading to release of enzymes from the lysosomes. The limited permeability of lysosomal membrane explains why lysosomal hydrolyses do not have a direct access to cellular components. Secondary lysosomes:These are also called the phagosomes as they contain the engulfed material and enzymes. Autophagic Vacuoles:The autophagic vacuoles are also known as autophogosomes or cytolysosoms.
The autophagic vacuoles are formed when the cell feeds on its intracellular organelles such as the mitochondria and endoplasmic reticulum by the process of autophagy. In such cases, the primary lysosomes are concentrated around the intracellular organelles and digest them ultimately.The autophagic vacuoles are formed in special pathological and physiological conditions.
The technique about the separation of the lysosomes has been developed in laboratory of de Duve. For the extraction of lysosomes, first of all the cells are homogenated in sucrose solution.Rapid mechanical rotation of the pestle ruptures the cells, setting the intracellular particles free in the medium.
Then successive centrifugation of the resulting homogenate produces fractions, which can be separated by microneedles. Lysosomal Digestion of External Particles:Large molecules are taken into the cell by the process called phagocytosis.


Exposure of the material to the lysosomal hydrolases occurs through fusion of the phagosome with a lysosome.
Once the molecules are digested, the digested products can diffuse out of the so-called digestive vacuole into the cytoplasm of the cell leaving the residue in the digestive vacuole. The digestive vacuole now moves on to the cell membrane where the so-called reverse phagocytosis or defecation occurs.2. Digestion of Intracellular Substance:In certain cases portions of the somehow, find their way inside the cell’s own lysosomes and are broken down. How do they get in, is not clear, and the role which autophagy plays in cell function can only be summarized.Proteins, fats and polysaccharides can all be synthesized, and stored in the cell. During the starvation of cell these stored food materials are digested by lysosomes to give energy. What stimulates autophagy to take place and how do the large molecules get into the lysosome is not clear.3. The hypothesis has been advanced that this is a built in mechanism for removing dead cells.In multi-cellular animals, many cells are constantly being formed, live for a short period of time, and then die. The self-digestion may occur as a pathological mechanism just for example, if a cell is cut off from its oxygen supply or poisoned, the lysosomal membrane may rupture, thereby permitting the enzymes to dissolve the cell. Extracellular Digestion:A cell can discharge lysosomal enzymes to destroy the surrounding structures. A pocket of enzymes from a lysosome is released outside the cell where it digests contagious structures. This is thought to explain, how sperms penetrate the protective coating of the ovum during fertilization.It may also explain how oesteoclast cells that destroy bones, function. This may also be the explanation for the well-known ability of white blood cells to pass quickly out of the blood vessels and into the tissues spaces at the site of an infection.5.
Role in Secretion:In recent years evidences have started accumulating to suggest the role of lysosomes in the formation of secretory products in secretory cells. The phenomenon of lysosomes- mediated thyroid hormones secretion is the best known example of direct lysosomes involvement in secretory process.Lysosomes also play possible role in the regulation of hormone secretion.
It is believed that mammotrophic hormones of the anterior pituitary is synthesized on the ribosomes of the rough endoplasmic reticulum and is packaged into secretory granules by passage through the Golgi.The epithelial cells of the thyroid also contain lysosomes rich in lysosomal enzymes. The follicles of the thyroid gland contain high molecular weight protein thyroglobulin, which is stored as colloid in the lumen. The thyroid hormones thyroxine and thriiodothyroxin are linked with this protein.The colloid containing thyroglobulin enters the epithelial cell by pinocytosis.
The colloid droplets fuse with primary lysosomes to form secondary lysosomes or digestive vaculoles.


Good evidences have accumulated on the role of lysosomes in involution of uterus and mammary glands immediately in postpartum.
During metamorphosis, the process of resorption of the tadpole tail and regression of the various larval tissues, including the fat body and the salivary gland, are accompanied by increased lysosomal acid hydrolase activity (Weber).8. Role of Lysosomes during Cell Division:During the cell division, the lysosomes of the particular dividing cell move towards the periphery instead of near the nucleus, as in usual cases they are seen.
During the cytokines is roughly equal number of them move towards opposite poles.Sometimes during cell-division certain repressors in cytoplasm inhibit call-division.
Lysosomes secrete certain depressors which destroy the repressor and results in cell division (Allison, 1967).10. Help in protein synthesis:Novikoff and Essner (1960) have suggested the possible role of lysosomes in protein synthesis. In the liver and pancreas of some birds, lysosomes seem to be more active and developed showing possible relationship with cell metabolism.11.
The partial deletion of chromosome 21 in man is associated with the chronic myeloid leukemia (blood cancer).12. Removal of dead cells:Hirsch and Cohn (1964) suggested that lysosomes help in the removal of dead cells in tissue. The lysosomal membrane raptures in these cells, releasing the enzyme into body of cell, so that whole cell may be digested. Fertilization:During fertilization the sperm releases hydrolytic enzymes from the acrosome vesicle. Fluorescence microscopic studies of acridine-stained spermatozoa of the guinea pig show that the acrosome vesicles contain several enzymes, including hyaluronidase and proteases, which are also found in lysosomes.In fact, the acrosome vesicle has been looked upon as a giant lysosome.
The acrosome vesicle enzymes also apparently activate the egg by breaking down its cortical granules.14.
The particles of silica or asbestos increase the permeability of lysosomal membranes and rapture of lysosomes. This leads to the lysis of lung cells resulting in their inflammation.A metabolic disorder, the gout, is caused by the accumulation of sodium orate crystals in the joints.
Pomes disease is another example which is caused due to absence of a lysosomal enzyme which hydrolize the glycogen.




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