Lysosomes, Peroxisomes & Secretory Vesicles
are membrane-bound vesicles.
are formed from endoplasmic reticulum-Golgi apparatus system.
Lysosomes
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.
Functions
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.
Types
Primary Lysosomes
are freshly formed inactive lysosomes.
Secondary Lysosomes
are formed by fusion of primary lysosome with phagosome or endosome.
are actively digesting things.
Peroxisomes
are formed by pinching off from smooth endoplasmic reticulum.
Contains oxidase enzymes e.g. catalase
Functions
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.