LYSOSOME
LYSOSOMES:-
They were discovered accidentally by a Belgian scientist,Christian de Dive,in 1955 through fracionantion technique.
Lysosomes are small vessicles which are bounded by a single membrane and contain hydrolytic enzymes in the form of minute crystalline or semicristaline granules of 5-8 nm. About 50 enzymes have been recorded to occur in them. All the enzymes Do not occur in the same lysosome but there are different sets of enzymes in different types of Lysosomes. The important enzymes are acid phosphatases, sulphatases,p peptidases,nucleases,lipases and carbohydrases. They are also called acid hydrolases because these digestive enzymes usually function in acidic medium or pH of 4-5. Acidic conditions are maintained inside the Lysosomes by pumping of H+ or proton into them. The covering membrane of Lysosomes keep the hydrolytic enzymes out of contact from cellular contents. Lysosomes are called suiside bags because of the presence of a large number of diagestive enzymes or acid hydrolases in them.
Lysosomes are generally rounded but can be irregular in outline. The diameter varies from 0.2-0.8 micrometer but sometimes it may grow to a very large size e.g upto 5 micrometer in leucocytes , kidney cell etc.
Lysosomes pass through various stages in the same cell. The phenomenon is called polymorphism or existence of more than one morphological form.Depending upon their morphology and function,there are four types of lysosomes-
1)primary Lysosomes
2) secondary Lysosomes
3)Residual bodies
4)Autophagic vacuoles
1) PRIMARY LYSOSOMES:- They are newly pinched off Vesicles from the Golgiapparatus which generally fuse with some endosomes to become fully functional. The primary Lysosomes are small in size. They contain hydrolytic enzymes in the form of granules.
2) SECONDARY LYSOSOMES:- They are also called "heterophagosomes" or "digestive vacuoles". A secondary Lysosome is formed by the fusion of food containing phagosome with Lysosome.Digestion occurs.The digested food passes out into the cytoplasm. Finally,the secondary lysosome is left with undigested food.
They were discovered accidentally by a Belgian scientist,Christian de Dive,in 1955 through fracionantion technique.
Lysosomes are small vessicles which are bounded by a single membrane and contain hydrolytic enzymes in the form of minute crystalline or semicristaline granules of 5-8 nm. About 50 enzymes have been recorded to occur in them. All the enzymes Do not occur in the same lysosome but there are different sets of enzymes in different types of Lysosomes. The important enzymes are acid phosphatases, sulphatases,p peptidases,nucleases,lipases and carbohydrases. They are also called acid hydrolases because these digestive enzymes usually function in acidic medium or pH of 4-5. Acidic conditions are maintained inside the Lysosomes by pumping of H+ or proton into them. The covering membrane of Lysosomes keep the hydrolytic enzymes out of contact from cellular contents. Lysosomes are called suiside bags because of the presence of a large number of diagestive enzymes or acid hydrolases in them.
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| (Structure of Lysosome) |
Lysosomes are generally rounded but can be irregular in outline. The diameter varies from 0.2-0.8 micrometer but sometimes it may grow to a very large size e.g upto 5 micrometer in leucocytes , kidney cell etc.
Lysosomes pass through various stages in the same cell. The phenomenon is called polymorphism or existence of more than one morphological form.Depending upon their morphology and function,there are four types of lysosomes-
1)primary Lysosomes
2) secondary Lysosomes
3)Residual bodies
4)Autophagic vacuoles
1) PRIMARY LYSOSOMES:- They are newly pinched off Vesicles from the Golgiapparatus which generally fuse with some endosomes to become fully functional. The primary Lysosomes are small in size. They contain hydrolytic enzymes in the form of granules.
2) SECONDARY LYSOSOMES:- They are also called "heterophagosomes" or "digestive vacuoles". A secondary Lysosome is formed by the fusion of food containing phagosome with Lysosome.Digestion occurs.The digested food passes out into the cytoplasm. Finally,the secondary lysosome is left with undigested food.
3)RESIDUAL BODIES:- They are those Lysosomes in which only indigestible food materials have been left. The residual bodies or Lysosomes pass outwardly and fuse with the plasma membrane to throw out the debris into external environment by exocytosis or ephagy.
4) AUTOPHAGIC VACUOLES:- They are produced by the fusion of a number of primary Lysosomes around worn out or degenerate intracellular organelles. The latter are first wrapped over by one or two membranes from endoplasmic reticulum before recognised by Lysosomes. The cell debris is digested. The phenomenon is also called autophagy or autodigestion.
FUNCTION OF LYSOSOMES:-
1) Intracellular Digestion:- Individual cells may obtain food through phagocytosis. The same is digested with the help of Lysosomes.
2) Extracellular Digestion:- For this the Lysosomes release enzymes In the external environment through exocytosis.
3)Body Defence:- Lysosomes of leucocytes devour foreign proteins,toxicsubstances, bacteria and other microorganisms.They thus take part in natural defence of the body.
4) Intracellular scavenging:- In long lived cells the Lysosomes perform Intracellular scavenging by removing old or useless organelles.
5) Sperm lysins:- They are lysosomal enzymes which are used for breaking limiting membrane of eggs.
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