Lysosomes

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Name :- Lysosomes, garbage system of the cell, suicidal bag of the cell

Properties :
  1. These are membrane bound vesicular structures founds throughout the cytoplasm.
  2. These are formed by the process of packaging in the golgi apparatus.
  3. Enzymes of lysosomes are synthesized in rough endoplasmic reticulum.
  4. Among the organelles, the lysosomes have the thickest covering membrane that is formed by a bilayered lipid material.
  5. Lysosomes have 50 different hydrolytic enzymes, known as acid hydroxylases.
Types of Lysosomes :
  1. Primary lysosomes, this is an inactive of form of lysosomes.
  2. Secondary lysosomes, this is an active form of lysosomes (lysosomes active during phagosome or endosome and at this time lysosomes pH become acidic and enzymes are activate).
Lysosomal Enzymes : 
  1. Proteases :- which hydrolyze the proteins into amino acids.
  2. Lipases :- which hydrolyze the lipids into fatty acids and glycerides.
  3. Amylases :- which hydrolyze the polysaccharides into glucose.
  4. Nucleases :- which hydrolyze the nucleic acids into mononucleotides.
Mechanism of action :
  1. Heterophagy - Digestion of extracellular material engulfed by the cell by endocytosis.
  2. Autophagy - Digestion of intracellular material such as worn-out cytoplasmic organelles.
Functions : 
  1. Degradation of macro-molecules, by phagocytosis or phagosome or vacuoles, and by pinocytosis or receptor mediated endocytosis or endosomes. 
  2. Degradation of worn-out organelles, by autophagosomes.
  3. Removal of excess secretory product in the glandular cells.
  4. Secretory function (conventional lysosomes are modified into secretory lysosomes by combining with secretory granules) like...
    1. Lysosomes in the cytotoxic T lymphocytes and natural killer (NK) cells secrete perforin and granzymes, which destroy both viral-infected cells and tumour cells.
    2. Melanocytes secrete melanin which have protective action for skin.
    3. Mast cells secrete serotonin which act as a vasoconstrictor and inflammatory mediator.
Lysosomes



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