Do Eukaryotic Cells Have Lysosomes?9 Facts You should Know


In this post you will find the information about do eukaryotic cells have lysosomes, their functions, structure, composition and more detailed facts around it.

All eukaryotic cells posses lysosomes except erythrocytes and some plant cells. Lysosomes develops as Golgian vacuoles from Golgi apparatus. They are formed when endosomes combined with Golgian vesicles. Lysosomes are the digestive sacs of the cell. They mainly functions as intracellular digestion of macromolecules.

Do eukaryotic cells have lysosomes ?

All eukaryotic cells have lysosomes except erythrocytes. They are main component of protistan, protozoans and animal cells. The presence of lysosomes can also been seen in fungi, seeds and root tips of some plants. Plant cell also lacks lysosomes but other cell organelle performs the functions of lysosomes like vacuoles, aleurone grains and sphaerosomes.

How many lysosomes are in a eukaryotic cell?

In eukaryotic cell, the number of lysosomes is in the range of 50-1000. This number can vary depending upon the function. Like leucocytes, macrophages and histocytes have contains large number of lysosomes because their main function is to combat the unwanted substances and they work more efficiently if the number of lysosomes is high.

Phagocytic cells like macrophages have high number of lysosomes because they act as a barrier for unwanted substances which  enters into the body. Lysosomes contain large number of acid  hydrolytic enzymes. The number of these enzymes is about more than fifty. The size of lysosome ranges between 0.2-0.8μm in diameter. Lysosomes are single membrane bound organelle and works at acidic pH because they mainly consists acid hydrolases enzymes.

How are lysosomes formed in a cell?

Lysosomes develops as Golgian vacuoles from Golgi apparatus. They are formed when endosomes combined with Golgian vesicles. Endosomes are the secretions from the plasma membrane which fuse with vesicles to form lysosomes.

Basically, endosomes are also vesicle like structure which are released by the plasma membrane from outside to inside the cell by endocytosis. These endocytosis remains inside the cell for few time and are referred to as late endosomes. As Golgi  complex releases the vesicles, these vesicles get fuse with endosomes to make lysosomes. The formed lysosomes contains hydrolytic enzymes that are synthesized in the endoplasmic reticulum.

Eukaryotic cell lysosome function

  • Lysosomes are the digestive sacs of the cell. They mainly functions as intracellular digestion of macromolecules.
  • Macrophages and other leucocytes have high number of lysosomes in them. They work on removing and digesting the unwanted microbes that do not belongs to the eukaryotic cell.
  • Macrophages engulf the microbes and other pathogens by phagocytosis and collects them in a sac called phagosome. These phagosome fuses with the lysosome present in the macrophage and forms the structure called phagolysosome.
  • Lysosomes also helps in hormone elaboration, protein molecules are present in thyroid glands which are broken down to produce thyroid hormones.
  • Lysosomes seems to remove repressors and helps in the process of mitosis.
  • Lysosomes perform autophagy, a condition in which cell lacks nourishment due to starvation, lysosomes break down proteins and other cell organelle to provide nourishment to the cell.
  • Lysosomes also removes the obstruction caused in the body .
  • It also performs regression of the useless products formed in the body. For example when child is born, the uterus weighs about 5kg, after parturition it weighs only 50 grams, this regression is done by lysosomes.
  • The worn out organelles are also digested by the lysosomes.
  • Patients suffering from joint problems get deposition of bony substances in their joints, macrophages move to the site and releases lysosomes that dissolve the deposition in the joints.

Eukaryotic cell lysosome structure

Eukaryotic lysosomes have round morphology  surrounded by single membrane. The size ranges between 0.2-0.8 μm in diameter. The membrane that surrounds the lysosome is resistant to enzymes enclosed by it due to high degree of glycosylation of its proteins and lipids. Inside the lysosome, finely granular fluid is present along with the digestive enzymes.

Each lysosome contains about fifty hydrolytic enzymes, the number of enzymes may vary according to cell types. The enzymes mainly work in acidic pH because they are acid hydrolases. Nucleases, proteases, lipases, phosphatases and lysozyme are the important enzymes that are present in lysosomes.

TEM views of various vesicular compartments. Lysosomes are labelled by “Ly”. They can be seen dark in the image due to their acidic nature, Golgi Apparatus can be seen, distal from the cell membrane relative to the lysosomes from Wikipedia

The membrane of lysosome are embedded with cortisol, cholesterol, chloroquine and antihistamine etc. These structures are called membrane stabilizers. There are also some substances like fat soluble vitamins, hormones, bile salts and X rays which make the lysosomal membrane weak and fragile.  They are called membrane labilisers.

Location of lysosomes in eukaryotic cell

Lysosomes occurs in cytosol of the cytoplasm  in eukaryotic cell. Lysosomes  are formed when endosomes combined with Golgian vesicles. Endosomes are the secretions from the plasma membrane which fuse with vesicles to form lysosomes.

Basically, endosomes are also vesicle like structure which are released by the plasma membrane from outside to inside the cell by endocytosis. These endocytosis remains inside the cell for few time and are referred to as late endosomes. As Golgi  complex releases the vesicles, these vesicles get fuse with endosomes to make lysosomes.

Composition of lysosomes

Lysosomes are basically secretory vesicles released from the Golgi complex. Its membrane is mainly composed of proteins and lipids. The membrane of lysosome are embedded with cortisol, cholesterol, chloroquine and antihistamine etc. These structures are called membrane stabilizers.

The lumen of lysosomes are filled with fine granular fluid that contains hydrolytic or digestive enzymes. There are also some substances like fat soluble vitamins, hormones, bile salts and X rays which make the lysosomal membrane weak and fragile.  They are called membrane labilizers.

Which cells do not have lysosomes?

Plant cells do not contain lysosomes, the function of lysosomes is carried out by other organelle like vacuoles, aleurone grains and  sphaerosomes. Plant cell do not require lysosomes because they have cell wall which act as a protective barrier and doesn’t allow the entry of unwanted substances inside the cell.

For digestion of other macromolecules, there is a large vacuole present inside the plant cell and other supporting organelle like sphaerosomes that helps in the digestion.

Lysosome polymorphism

Lysosomes can be found in different morphological and physiological forms. This phenomenon is called lysosome polymorphism. Basically, they are divided into primary and secondary lysosomes. Secondary lysosomes are further of three kinds, heterophagosomes, autophagosomes and residual bodies.

Do Eukaryotic Cells Have Lysosomes
Types and function of lysosomes

1.Primary lysosomes

They are true lysosomes and are first formed from the distal maturing face of Golgi body. After formation they are distributed evenly in the cytosol by fusing with endosomes which probably bring in proton pumping machinery.

2.Heterophagosomes, Heterolysosomes or digestive vacuoles

They are formed by the fusion of phagosomes and pinosomes with primary lysosomes. Basically, phagosome brings the food materials from outside the cell and depending upon their size, 2-3 primary lysosomes are combined with them to form heterophagosome or big digestive vacuole. They break down the substance into smaller particles and diffuse them  through membrane for the metabolism.

3.Autophagosomes, Autolysosomes, Cytolysosomes or autophagic vacuoles

These structures are formed when starvation of cell occurs. When there is not enough food materials are there for cell to obtain energy, these structures perform autophagy. Autophagy is the eating of cell structures and organelles in order to make survival of the cell. The unwanted cell organelle is enclosed by smooth membrane called isolation body. Primary lysosomes fuses with isolation body to form autophagic vacuole.

4.Residual bodies

They are secondary lysosomes which are formed to store undigested material dispose off from autophagic vacuole. These residual bodies discharge the waste outside the cell through ephagy or exocytosis.

Difference between autophagy and autolysis

AutophagyAutolysis
It is digestion of reserve food stuff or cell organellesComplete digestion of the cell.
Formation of an isolation body occurs.No isolation body is formed.
Primary lysosomes are combined with isolation body to form autophagosomes.No such fusion occurs  and a vacuole like structure is not formed.
Membrane of vacuole does not break down.Lysosomal membrane breaks off.
Enzymes remain inside the vacuole .Enzymes are released into the cytoplasm.
It is resorted for intracellular digestion during starvation.It is resorted for removing complete cell or tissues.

Conclusion

To wrap up this post , we conclude that all eukaryotic cells possess lysosomes except some plants cells. Lysosomes can be found in different morphological and physiological forms. This phenomenon is called lysosome polymorphism. Lysosomes develops as Golgian vacuoles from Golgi apparatus. They formed when endosomes combined with Golgian vesicles. Endosomes are the secretions from the plasma membrane which fuse with vesicles to form lysosomes.

Saif Ali

Hi, I am Saif Ali. I obtained my Master's degree in Microbiology and have one year of research experience in water microbiology from  National Institute of Hydrology, Roorkee. Antibiotic resistant microorganisms and soil bacteria, particularly PGPR, are my areas of interest and expertise. Currently, I'm focused on developing antibiotic alternatives. I'm always trying to discover new things from my surroundings.  My goal is to provide readers with easy-to-understand microbiology articles. If you have a bug, treat it with caution and avoid using antibiotics to combat SUPERBUGS. Let's connect via LinkedIn.

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