What are lysosomes? – Structure, function and types
Lysosomes are very important cellular organelles found in most eukaryotic cells, which are full of enzymes that break down molecules large ones into simpler ones that the cell can reuse.
Lysosomes have a wrinkled inner membrane, and their enzymes need work in an acidic environment. Also, there are different types of lysosomes, each with specific enzymes and different jobs. Let’s see more about them!
Definition and concept of lysosomes
They are cellular organelles present in eukaryotic cells that contain hydrolytic enzymes capable of degrading unnecessary or damaged cellular and extracellular materials. They are different from peroxisomes, which are responsible for the oxidation of fatty acids and the elimination of toxic substances from cell metabolism, such as hydrogen peroxide.
These organelles are spherical and have a diameter of approximately 0.1 to 1 micrometer. They are surrounded by a lipid membrane that prevents lysosomal enzymes from damaging the rest of the cell. In addition, they have a high internal acidity due to the presence of proton pumps that maintain a Optimum pH for enzyme activity.
They fulfill the function of break down large molecules into smaller ones for reuse by the cell. These organelles are involved in a wide variety of cellular processes, including:
- The digestion of food in animal cells.
- The degradation of damaged or aged cell organelles.
- removal of pathogens and foreign materials that are phagocytosed by the cell.
In addition to their crucial role in cellular digestion, they are also involved in cell signaling processesregulation of cell growth and death.
Lysosomal disorders, such as Tay-Sachs disease or Gaucher disease, can have serious health consequences by preventing lysosomes from functioning properly and removing cellular debris. These diseases are characterized by accumulation of indigestible materials in lysosomes due to the lack or decrease of any of the hydrolytic enzymes.
What function do lysosomes have?
The main function of lysosomes is the intracellular digestion extracellular and intracellular materials. These fuse with the vesicles that contain the materials to be digested and release their enzymes inside these vesicles.
It is a cellular organelle that contains hydrolytic enzymes, that is, they can break down and digest complex molecules. In this way, they are responsible for the digestion of foreign materials that enter the cell, such as bacteria, viruses, and damaged particles.
They also participate in the degradation of cell components that are no longer useful or that have completed their life cycle, such as old proteins and aged or damaged organelles, a process known as autophagy. In addition, they are involved in the digestion of nutrients that the cell needs to obtain energy and maintain its metabolic functions.
Thanks to this they are organelles key to maintaining cellular homeostasis and the protection of the cell against pathogens, preventing internal damage.
They also play an important role in the apoptosis or programmed cell death. In this process, they release their enzymes into the cell’s cytoplasm, which contributes to the degradation of the cell.
What are the characteristics of lysosomes?
The characterization of lysosomes can be defined as follows:
- They are spherical and membranous organelles. containing hydrolytic enzymes. They are spherical or oval in shape and are surrounded by a membrane that separates them from the cytosol.
- contain hydrolytic enzymes (which catalyze the hydrolysis of molecules) capable of degrading proteins, lipids, carbohydrates and nucleic acids.
- They can fuse with vesicles they contain materials that need to be broken down, in order to release their enzymes and digest them.
- Can fuse with the plasma membrane to release their enzymes outside the cell and digest extracellular materials.
- They are present in eukaryotic cells and originate from the Golgi apparatus.
- They have a acid pH (about 5), which allows them to activate and stabilize hydrolytic enzymes.
- They have the ability to self-destruct if they detect an alteration in its functioning, thus preventing their enzymes from damaging the cell. Although, in certain circumstances, such as in situations of cellular stress, they can break down and release their enzymes to the cytoplasm of the cell. This can lead to self-digestion of the cell and its death.
In summary, they are essential organelles for the degradation of cellular substances and the elimination of extracellular materials, thanks to their content in hydrolytic enzymes and its melting capacity with other cell structures.
What is the structure of lysosomes?
Its structure may vary based on its content and function. Primary lysosomes, also called pre-lysosomesare vesicles that form in the rough endoplasmic reticulum and travel through the Golgi apparatus to mature into functional lysosomes.
Mature lysosomes can have different shapes and sizes, and contain different hydrolytic enzymes depending on the cell type and the function they perform. Some might even have additional structures, such as glycogen inclusions or residual bodies, which are the indigestible remains of intracellular digestion.
The general structure of lysosomes is as follows:
- Membrane: They are surrounded by a lipid membrane that protects the hydrolytic enzymes contained within.
- Acid hydrolases: The content of the lysosome is acidic and contains various acid hydrolases (hydrolytic enzymes) that break down organic molecules. They are capable of degrading macromolecules such as proteins, lipids, carbohydrates, and nucleic acids into their basic components.
- Membrane protein: Lysosome membrane proteins help transport materials to and from the organelle.
- dense core: The dense core is a region in the center of the lysosome that contains hydrolytic enzymes. highly active.
- Vesicles: They can also fuse with vesicles that contain cellular materials to be degraded.
What type of cell are lysosomes?
They are found mainly in animal cell or eukaryote and they are a kind of vesicles that contain acid hydrolases, which are enzymes capable of breaking down complex molecules such as proteins, lipids, and carbohydrates.
The reason for their cell type is that they are organelles typical of eukaryotic cells, that is, they come from cells that have a nucleus surrounded by a nuclear membrane, as well as other membranous organelles such as the endoplasmic reticulum, Golgi apparatus and mitochondria. They originate from the Golgi apparatus and are transported throughout the cell via the cytoskeleton.
Where are lysosomes from?
They are organelles that originate in the golgi apparatus of the cell. During their formation, hydrolytic enzymes are synthesized in the rough endoplasmic reticulum and then transported to the Golgi apparatus for processing and packaging in lysosomal vesicles.
These vesicles fuse with the late endosomes and primary lysosomes to form mature lysosomes that contain the hydrolytic enzymes necessary to break down unwanted cellular materials. Therefore, it can be said that lysosomes have a golgian origin.
Explaining in more detail, once formed, lysosomes make their way to the early endosomes and fuse with them to form late endosomes. These then bind to the mature lysosomes to release the hydrolytic enzymes within and break down cell materials that are there.
What are lysosomes capable of?
Thanks to their content of hydrolytic enzymes, they are capable of break down and recycle cellular materials that are no longer needed or that are harmful to the cell, such as proteins, lipids, carbohydrates, and nucleic acids. There is also a kind of specialized lysosome contained in the cell membrane, called vacuolewhich is responsible for eliminating waste and residues from the contents of the cell.
They are involved in cellular processes such as autophagy (the degradation of cell components such as damaged or aged organelles), apoptosis (programmed cell death) and the immune response, since they can degrade bacteria and viruses that have been engulfed by cells.
How many types of lysosomes are there?
There is no talk of different types of lysosomes as such, but they can be classified based on their origin and their enzyme content.
- Primary lysosomes: are organelles that form in the rough endoplasmic reticulum are processed in the Golgi apparatus. These contain hydrolytic enzymes that are capable of degrading and recycling various cellular materials.
They are the precursors of mature lysosomes, which are formed by the fusion of primary lysosomal vesicles with other cell membranes, such as endosomes and phagosomesto then perform various functions such as the digestion of foreign substances and the regulation of cellular metabolism.
Defects in their formation and function are related to several rare genetic pathologies, known as lysosomal diseaseswhich can cause severe and life-threatening symptoms in affected individuals.
- Secondary lysosomes: They are formed from the fusion of primary lysosomes with vesicles containing material to be degraded. They are those that have fused with other cellular organelles, such as endosomes, phagosomes, or autophagosomesto form larger structures called residual bodies, which are removed from the cell by processes of exocytosis or autophagy.
- Autophagous lysosomes: It is a type of lysosome that is responsible for degrading its own cellular components that have been damaged, aged or not needed for the cell. This process is called autophagy and is important for the maintenance of cellular homeostasis.
Autophagy is a process of cell degradation that involves the formation of a membrane that surrounds the cellular components that are going to be degraded, thus forming a structure called autophagosome.
Is essential for cell survival and the prevention of diseases, because when it does not work correctly, components that cause neurodegenerative disorders, cancer and other pathologies can accumulate.
- Heterophageal lysosomes: They originate from the fusion of endocytic vesicles with the lysosomes. These endocytic vesicles are those that are formed from the intussusception of the cell membrane and that capture material from outside the cell to be degraded.
Heterophages are responsible for the degradation of materials external to the cell, such as bacteria, viruses, dead cells and other particles that are phagocytosed by the cell. They are also very important for the immune system, where phagocytic cells use these organelles for eliminate pathogens and other foreign materials from the body.