Lysosomes: Types and Functions

  • They were first of all observed by Christian de Duve in 1955.
  • The lysosomes are tiny vesicles which are bounded by single membrane and are made from proteins and lipids.
  • They are found in different organisms like in most of the animal cells and only in a few plant cells like yeast, fungi and in green unicellular organisms.
  • They are absent in bacteria and mature mammalian erythrocytes.
  • They are originated from endoplasmic reticulum or from the vesicles of the Golgi complex.
  • They contain many enzymes about 40 kinds of enzymes that are involved in intracellular digestion.
  • The enzyme includes proteases that helps in protein digestion, nucleases, glycosidases (helping in digestion of polysaccharides), lipases, phosphatases (phosphate linked compounds) and sulphatases (sulphate linked compounds).
  • The internal pH of the lysosome is about 5, which is two units lower than that of the cytoplasm.
  • So, the hydrolytic enzymes within the lysosomes function optimally at this pH.
  • These hydrolytic enzymes are nonspecific in their activity and could potentially destroy key cellular macromolecules if not contained.

Types of Lysosomes

The lysosomes are grouped into four types. They are:

i) Primary lysosome: These are newly formed small bodies which contain hydrolytic enzymes in inactive state and are the pinched off  vesicle from the golgi apparatus.

ii) Secondary lysosome: The primary lysosome fuses with the vacuoles containing extracellular or intracellular substances and form secondary lysosome. They are also known as heterophagosomes or digestive vacuoles.

iii) Residual body: The lysosomes with undigested bodies are called residual bodies. These are also called tertiary lysosomes.

iv) Autophagic vacuole: Lysosomes are able to digest cell organelles due to which they are known as autophagic lysosomes.



  • They digest the particles that enter the cell like food particles.
  • In some pathological conditions, the lysosomes start to digest the various cell organelles and cause ultimately the death of the cell which is known by the process autolysis or cellular autophagy.
  • For this reason, the lysosomes are also known as suicidal bags.
  • They digest disease causing microorganisms.
  • They also digest worn-out and the dead cells.

lysosomes and its functionsको लागि तस्बिर परिणाम                   lysosomes and its functionsको लागि तस्बिर परिणाम


  • The lysosomes of sperms discharge their enzymes and digest the limiting membrane of the ovum at the time of fertilization.
  • Lysosomes are involved in formation of bone cells as well as their destruction.
  • Ageing of cells as well as parthenogenetic development are also related with lysosomal activity.
  • Lysosomes have been found to be involved in protein synthesis in case of some birds.
  • They have role in metamorphosis of frog.





Lysosomes: Types and Functions