Index
It is a subcellular organelle found in almost all types of eukaryotic cells.
Each lysosome is surrounded by a membrane that maintains an acidic environment through a proton pump. Lysosomes contain many hydrolytic enzymes (acid hydrolases) that break down macromolecules such as nucleic acids, proteins, and polysaccharides.
These enzymes are active only in the acidic interior of the lysosome; their acid-dependent activity protects the cell from autodegradation in the event of lysosomal leakage or breakdown since the cell’s pH is neutral to slightly alkaline.
History
Lysosomes were discovered by the Belgian cytologist Christian René de Duve in the 1950s. This discovery was awarded the Nobel Prize in Physiology or Medicine in 1974.
Formation of lysosomes
Lysosomes originate by sprouting from the membrane of the trans-Golgi network, a region of the Golgi complex responsible for classifying newly synthesized proteins, which can be designated for use in lysosomes, endosomes, or the plasma membrane.
The lysosomes then fuse with membrane vesicles derived in one of three ways: endocytosis, autophagocytosis, and phagocytosis.
A lysosome is a specialized vesicle that contains a variety of enzymes. The enzyme proteins are first created in the rough endoplasmic reticulum.
Those proteins are packed into a blister and sent to the Golgi apparatus. The Golgi then does its final work to create digestive enzymes and remove a specific small vesicle. That vesicle is a lysosome.
From there, the lysosomes float in the cytoplasm until they are needed. Lysosomes are single membrane organelles.
Function
Lysosomes are responsible for digesting macromolecules, old cell parts, and microorganisms.
The purpose of the lysosome is to digest things. They can be used to digest food or break down the cell when it dies.
Lysosomal action
Since lysosomes are little digestion machines, they go to work when the cell absorbs or eats something. Once the material is inside the cell, the lysosomes bind and release their enzymes.
Enzymes break down complex molecules that can include complex sugars and proteins.
What happens if food is scarce and the cell starves?
Lysosomes will function even if there is no food for the cell. When the signal is sent, the lysosomes digest the cells’ organelles searching for nutrients.
Lysosomal function disorders
There are approximately 30 relatively rare disorders in humans due to defects in endolysosomal function. All are caused by errors in the genetic code, and all are lysosomal storage disorders.
In these disorders, the products accumulate in the lysosomes because the enzymes that would accelerate their degradation are absent or defective. Each condition has a specific medical name.
Some of the better-known disorders include:
- I cell disease: Fibroblast cell lysosomes are deficient in almost all hydrolytic enzymes, and large undigested “inclusions” accumulate in patient cells.
- Tay-Sachs disease – a lysosomal storage disorder in nerve cells, almost always causes premature death, but the incidence of death is now decreasing thanks to genetic testing and counseling.
- Pompe and Gaucher: Large amounts of lipids accumulate in lysosomes.
- Hurler syndrome: involves a defect in the metabolism of mucopolysaccharides; it is a lysosomal storage disease.
