lysosomes are organelles found in eukaryotic cells, being absent in prokaryotic cells. They are characterized by being membranous sacs full of enzymes inside, which act in the degradation of different molecules. Due to this characteristic, we can say that lysosomes are organelles dedicated to intracellular digestion.
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Summary about lysosomes
- lysosomes are organelles which are characterized by being membranous sacs full of enzymes.
- Enzymes present in lysosomes are involved in intracellular digestion.
- These organelles cause particles captured by cells to be degraded.
- They act in the recycling of parts of the cell itself (autophagy).
- Some lysosomes arise from the budding of the Golgi complex.
What are lysosomes?
lysosomes are organelles formed by small sacs rich in digestive enzymes. Different enzyme types are found inside lysosomes, such as enzymes that degrade proteins, phospholipids and nucleic acids. These organelles generally have a spherical shape and a diameter that varies between 0.05 µm and 0.5 µm.
They are membranous organelles, and the unique membrane that surrounds this structure ensures that enzymes present in its interior do not come into contact with the cytosol. If this happens, the cell has another protection: the pH of the cytosol, which is approximately 7.2. This makes the enzymes not very active, as they are optimally active only at acidic pH, and a pH of 7.2 is neutral.
Important: If several lysosomes break down and release their enzymes at the same time, the cell can be destroyed by self-digestion.
In addition to ensuring that enzymes do not come into contact with the cytosol, the lysosome membrane promotes the transport of digestion products to the cytosol so that they can be released out of the cell. cell or else be used by her. The membrane also helps to pump H+ into the lysosome, which ensures that the pH is acidic.
Digestive enzymes and lysosomal membranes are produced in the endoplasmic reticulum and processed in the Golgi complex. Some lysosomes arise from the budding of the Golgi complex.
What is the function of lysosomes?
Lysosomes are organelles that act in intracellular digestion, helping, for example, in the degradation of molecules captured by cells. Eukaryotic cells (which have a core bounded by a nuclear envelope), through a process known as endocytosis, are able to capture:
- particles;
- molecules;
- liquids.
In this process, a small portion of the plasma membrane engulfs the material to be ingested and forms a small vesicle inside the cell. Thus, two different actions can occur:
- Pinocytosis: endocytosis which involves the ingestion of fluid and molecules by small vesicles.
- Phagocytosis: endocytosis which involves the ingestion of larger particles such as microorganisms.
In the case of phagocytosis, the formed vesicle fuses with lysosomes, which release the enzymes necessary for digestion. THE phagocytosis is carried out, for example, by the amoebas to capture their food. In the case of molecules and liquids captured by smaller vesicles, the contents are delivered to lysosomes through so-called endosomes.
Lysosomes, however, do not only act in the digestion of molecules and particles of origin external to the cell, that is, they also perform an autophagy process. In autophagy, they degrade parts of the cell itself, like aged organelles. By carrying out this process, lysosomes help to recycle these cellular components, releasing the obtained compounds for reuse.
See too: What are the stages of the cell cycle?
Which cells have lysosomes?
Eukaryotic cells are the only ones that contain lysosomes. Some authors claim that these organelles occur only in animal cells. Others, however, believe that they may also be present in plant cells, being generally not evident. Despite the differences, it is customary to admit that they are, organelles unique to animal cells.
