Lysosome - Definition, Structure and Function, Phagocytosis

What is Lysosome?

 

Also known as a suicidal bag or digestive bag or cellular garbage disposal.

Lyso- "dissolving"

Somes – “bodies”

Lysosomes are tiny sphere-shaped sac-like structures, bounded by a single membrane. It is filled with digestive enzymes (hydrolytic enzymes) that have the capability to break down a variety of biomolecules and ability to destroy foreign particles,  digesting cells and unwanted materials.

Lysosomes are generated by the golgi apparatus or Golgi complex.

If the cell is damaged, not repaired, lysosomes can help it to self-destruct in a process called programmed cell death, or apoptosis. It is the natural, regulated mechanism of the cell that removes unnecessary or dysfunctional components, cytoplasmic components, and organelles to the lysosomes for digestion.

The process by which worn-out (completely exhausted) organelles are digested is known autophagy (self-eater).

Lysosome breaks or bursts inside its cell and the released enzymes that digest and degrade the cell. When it destroyed ownself is called autolysis.

Structure of Lysosome

 

Lysosomes are single membrane-enclosed vesicles formed from the Golgi complex.

 

The area within the membrane is known as the lumen, which contains digestive (hydrolytic) enzymes and other cellular debris. The pH level of the lumen is between 4.5 - 5.0, which makes an acidic environment.

 

The lysosome and its containing enzymes are synthesized separately.

The mRNA strands move to the RER (rough endoplasmic reticulum), where ribosomes construct the hydrolytic enzymes. Lysosomes have received the enzymes from the Golgi complex.

 

Inside the lysosome, there are 60 kinds of powerful digestive (hydrolytic) enzymes capable of breaking down large molecules.

 

 

Function of Lysosomes

 

1. The main function of lysosomes is digestion and removal of waste material of cell.

2. Cellular debris or foreign particles are pulled into the cell through the process of endocytosis and then engulf by lysosomes.

3. Lysosome contain hydrolytic enzymes that allow to destroy foreign particles, invading viruses and bacteria.

4. It contains a digestive enzymes that digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria, waste material.

 

5. Lysosome have many different function including - Lysosomal exocytosis, autophagy, and heterophagy (digestion of material extracellular environment).

6. Lysosome enzyme released at the site of injury that helps to digest cellular debris, which prepares the injured area for an effective repair.

 

7. Lysosomes help to defend against the entry of pathogens via endocytosis by degrading pathogens before they enter the cytoplasm.

 

8. Delivers discarded wastes, cytoplasmic components, organelles and other substances originating from within the cell is to the lysosomes for digestion and digested by the process of autophagocytosis or autophagy.

 

 

Role of Lysosomes in Phagocytosis

 

Lysosome contain hydrolytic enzymes that allow foreign particles to be destroyed.

Lysosomes play an important role in phagocytosis (involves the ingestion of solid material) or pinocytosis (ingestion of surrounding fluid).

For example,

 

1. Macrophages engulf the foreign particles or bacterium.

2. Then formation vacuole around engulf bacterium, called phagosome (vesicle formed around particle).

3. Then the fusion of the phagosome occurs with a lysosome to form a phagolysosome.

 

4. Then digestion of bacterium occurs, if the phagosome does not fuse with lysosomes and the bacterium avoids degradation.

5. Then the digested bacterium particles move out of the cell through exocytosis.