Lysosomes-Definition, Structure, Functions And Diagram

Lysosomes Definition

  • Hydrolytic enzymes found in dense, membrane-bound lysosomes are primarily in charge of intracellular and extracellular digestion.
  • The terms “lysis” and “soma,” which both imply “body,” are combined to form the word “lysosome.”
  • It is a crucial organelle in the cell that breaks down chemicals both within and outside the cell.
  • Animal cells have them more often, but just a few lower plant groupings do (slime moulds and saprophytic fungi).
  • Lysosomes are present in the cytoplasm at will. They are present in virtually all animal cells, with the exception of RBCs.
  • The cells involved in enzymatic processes, such as leucocytes, macrophages, renal, pancreas, and splenic cells, are where they are most often located.

Structure of Lysosomes

  • Lysosomes are pleomorphic, meaning they lack any distinguishing features of form or structure.
  • The majority of them have a spherical or granular look.
  • It is encircled by a single lipoprotein membrane that is different in composition and ranges in size from 0.2 to 0.5 m.
  • Highly glycosylated lysosomal associated membrane proteins (LAMP) and lysosomal integral membrane proteins (LIMP) are present in the membrane (LIMP).
  • LAMPs and LIMPs create a coat on the membrane’s inner surface.
  • They defend the membrane against the various hydrolytic enzymes kept within that may attack it.
  • A hydrogen proton pump located on the lysosomal membrane is in charge of regulating the pH of the enzyme. The lysosomal enzymes are guaranteed to operate by the acidic environment that is maintained by the proton pump, which pumps H+ inside the lumen.
  • The organelle houses crystalline enzymes inside the membrane.

Lysosomal Enzymes

Lysosomes include hydrolases, which are enzymes for degrading extracellular and intracellular substances. It encompasses roughly 40 different types of enzymes that fall under the following broad categories:

Proteases: Protein-digesting enzyme

Lipases:  lipids are broken down by lipases.

Amylase: breaks down carbs.

Nucleases:, which break down DNA and RNA,

Monoesters of phosphoric acid

The group of enzymes known as hydrolases as a whole cleaves substrates by adding water molecules to them. The majority of lysosomal enzymes work best in an acidic environment.

Types of Lysosomes

Primary Lysosomes

  • The small, sac-like structures that house the enzymes that the rough endoplasmic reticulum produces.
  • Enzyme storage granules are its common name.

Secondary Lysosomes

  • formed when phagosomes and primary lysosomes combine to form phagosomes.
  • They contain both enzymes and the ingested substance.
  • Digestive processes progress in stages.

Functions of Lysosomes

There are two main purposes for lysosomes:

1. Intracellular Digestion

  • The lysosome membrane joins with the food vacuole membrane to release the digestive enzymes.
  • Following digestion, the food diffuses past the vacuole membrane and enters the cell, where it is used for growth and energy.

2. Autolytic Action

  • By the process of autophagy, cell organelles that must be riddled are covered by vesicles or vacuoles to create autophagosomes.
  • Lysosomal enzymes then work to destroy the autophagosome.

Lysosomes are essential for a number of processes, including:


Phagocytosis is the process of ingesting foreign material into a cell by phagocytosis or pinocytosis, followed by the digestion of the material after the fusion of the newly formed vacuole with a lysosome.

B. Autophagy

A physiological process that occurs naturally in the body and involves cell death. It is necessary for maintaining homeostasis, for proper functioning by degrading proteins, and for the turnover of damaged cell organelles necessary for the production of new cells.

C. Extracellular Digestion

By exocytosis, primary lysosomes release hydrolases that break down extracellular materials.

Using fungus as an example,

D. Autolysis

It alludes to the destruction of a group of cells by the lysosomal membrane. It happens during the transformation of insects and amphibians.

E. Fertilization

An enormous lysosome called the acrosome of the sperm head ruptures and spews enzymes onto the surface of the egg. Through the breakdown of the egg membrane, this opens the door for sperm access into the egg.

F. As Janitors of the Cell,

By removing “garbage” from the cell, lysosomes assist in warding off illness.


  • Verma, P.S. and Agrawal, V..K. (1991). Cell biology, Genetics, Molecular Biology, Evolution and Ecology, S.Chand Company.
  • Kar,D.K. and halder,S. (2015). Cell biology genetics and molecular biology.Kolkata, New central book agency.
  • R and suwal,S.N. (2010).Human Anatomy and physiology. Kathmandu, vidyarthi prakashan (p.) ltd.
  • https://study.com/academy/lesson/lysosome-definition-function-quiz.html
  • https://biologydictionary.net/lysosome/
  • https://biologywise.com/lysosome-structure
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