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Lysosomes, Peroxisomes & Secretory Vesicles


  • Formed by breaking off from Golgi apparatus → disperse throughout the cytoplasm.

  • 250 to 750 nm in diameter.

  • Contains hydrolase enzymes that break larger molecules into fragments. e.g.

    • Proteases hydrolyze proteins into amino acids.

    • Amylases hydrolyaze polysaccharides into monosaccharides.

    • Lipases hydrolyze lipids into fatty acids and triglycerol.

  • Lysosomes are cell's digestive system. They degrade...

    • Damaged cellular structures.

    • Food particles.

    • Unwanted materials e.g. bacteria.

  • Recently lysosomes are found to be involved in secretory functions also.

  • Primary Lysosomes

    • are freshly formed inactive lysosomes.

  • Secondary Lysosomes

    • are formed by fusion of primary lysosome with phagosome or endosome.

    • are actively digesting things.


  • Catabolize long-chain fatty acids (β oxidation)

  • Detoxification: Oxidizes toxic substances that may be harmful to the cell.

Secretory vesicles

  • are also called secretory granules.

are formed from Golgi apparatus

Store substances that are to be released out of the cell

When cell is stimulated for release

Content of secretory vesicles is released intracellularly by exocytosis.


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