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CELL BIOLOGY

What are the functions of lysosomes?

Lysosomes: are organelles of the cytoplasm that contain enzymes (specifically, acid hydrolases ) that are responsible for assimilating the waste products (called metabolites) produced by cells. This assimilation is the work of proteins produced by the lysosome. For a protozoan, the lysosome is a real stomach that allows it to digest small organisms and other food particles. Important functions of lysosomes are the following.

1. Intracellular digestion

The word lysosome is derived from (lyso lytic or digestive, and soma body) thus helping digestion. Pinocytic vacuoles formed as a result of the absorption of fluid in the cell or phagocytic vacuoles formed by the absorption of solid particles in the cell transport the protein material to the lysosomal region.
These foreign proteins can undergo digestion in the cell as a result of endocytosis. Endocytosis includes the processes of phagocytosis (derived from a Greek word “phagein” meaning eating), pinocytosis (derived from a Greek word “Pinein” meaning drinking) and micropinocytosis.
After a particle or large body enters the cell through endocytosis and the formation of a phagosome, the membranes of the phagosome and a lysosome can fuse to form a single large vacuole. Within this vacuole, the lysosomal enzymes begin the process of digestion of foreign matter.

Initially, the lysosome, known as a primary lysosome containing the enzyme complex in an inactive state, but after fusion with the phagosome produces a secondary lysosome with a different morphology and active enzymes.
Many cellular components, such as the mitochondria, are constantly removed from the cell by the lysosomal system. The cytoplasmic organelles are surrounded by membranes of smooth endoplasmic reticulum, forming vacuoles, then the lysosomal enzymes are released into the autophagic vacuoles and the organelles are digested.

2. Removal of dead cells

Hirsch and Cohn (1964) stated that lysosomes help to remove dead cells from tissues such as white blood cells with bacteria engulfed in the blood, cells in the outer layer of the skin, and the mucous membranes of the body’s mucous membranes.

The lysosomal membrane ruptures in these cells, releasing enzymes into the cell body so that the whole cell can be digested. Lysosomes contain a sufficient complement of enzymes to digest most types of biological or organic matter and the digestive process (autolysis) occurs fairly quickly in dead cells. This process of tissue degeneration (necrosis) is due to this lysosomal activity.

3. Play a role in the metamorphosis:

Recently, the role of the lysosome was discovered in the metamorphosis of the frog. The disappearance of the tail of the frog tadpole larva is due to lysosomal activity (action of cathepsins present in lysosomes) as described by Weber.

4. Protein synthesis:

Novikoff and Essner (1960) suggested the possible role of lysosomes in protein synthesis. Recently, the author (Dr. Singh 1972) has correlated lysosomal activity with protein synthesis. In the liver and pancreas of some birds, lysosomes appear to be more active and to develop, as Singh (1972) indicates, showing a possible relationship with cellular metabolism.

5. Lysosomes help in Fertilization

During fertilization, the sperm head secretes certain lysosomal enzymes that help the sperm penetrate the yolk layer of the egg. Acrosome contains protease and hyaluronidase and abundant acid phosphatase. The hyaluronidase disperses the cells around the oocyte and the protease digests the pellucid area by creating a channel through which the sperm nucleus enters.

6. Role in osteogenesis:

It has been argued that the formation of bone cells and also their destruction depends on the lysosomal activity. Likewise, cell aging and parthenogenetic development are linked to the activity of lysosomes. The osteoclasts (multinucleated cells) that remove bone, do so by releasing lysosomal enzymes that degrade the organic matrix. This process is activated by the parathyroid hormone.

7. Lysosome dysfunction:

Lysosomal dysfunction can lead to illnesses, for example when the glycogen absorbed by the lysosomes is not digested (Pompe disease). Lysosome ruptures in skin cells exposed to direct sunlight cause pathological changes after sunburn. The enzymes released by these lysosomes kill the cells of the epidermis, causing blisters and later “peeling” of a layer of the epidermis.

8. Autolysis of cartilage and bone tissue:

Excess vitamin A causes cell poisoning. It can disrupt the lysosomal membrane and can cause the release of enzymes in the cell and produce autolysis in cartilage and bone tissue.

9- Lysosomal diseases

There are several diseases, each characterized by the absence of a lysosome enzyme. .A lysosomal disease is a disease, generally genetic, of the child and the adult, in connection with the abnormal functioning of one of the enzymes contained in the lysosome.There are about fifty lysosomal diseases, the common point of which is a genetic deficiency leading to dysfunction of the lysosome.

For each of the lysosomal diseases, a defect in a specific gene leads to the non-production or insufficient production of the protein responsible for the assimilation of specific cellular metabolites. Thus these metabolites then accumulate, causing the dysfunction of the organs concerned. Most of these diseases are progressive and poly-disabling. They cause physical and neurological handicaps for some of them. In all cases, these are rare diseases.

What is a lysosome?

A lysosome is an organelle found inside a cell. It is used to digest proteins, sugars (polysaccharides), lipids and nucleic acids. It also serves as a defense against viruses and bacteria.
Sheltering the cell, considering the damage that enzymes would cause if they circulated freely in the cytosol,
recycling of intracellular organic matter.
The lysosome can perform these functions because its ph is low and it is filled with enzymes

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