Living things are made up of cells, the basic unit of life. There are many types of cells:
- according to its evolutionary origin: prokaryotic and eukaryotic cell;
- according to your energy requirement: plant and animal cell;
- according to its functions: contraction, defense, transport, repair, among others.
Cell types according to their evolutionary origin
Depending on the evolutionary origin, we have two types of cells: prokaryotic and eukaryotic cells.
The prokaryotic cell is characterized by presenting its cellular content, especially the genetic material, dispersed in the cytoplasm. This means that the prokaryotic cell has two main structures: the plasma membrane and the cytoplasm, and has no nucleus.
The prokaryotic cell is the cell that distinguishes the Bacteria and Archaea domains. Most prokaryotic cells are small and simple in appearance and are widely distributed throughout the biosphere.
PROKARYOTIC CELL EXAMPLE
The Staphylococcus aureus is a Gram-positive bacterium so redondeada`que can be found in the skin and mucous membranes of humans. Infections by this agent have increased due to antibiotic-resistant strains.
The eukaryotic cell is characterized by presenting its cellular content organized in membrane compartments, in particular, the genetic material (DNA) that is confined to the nucleus. In this way, the eukaryotic cell has three main structures:
- The plasma membrane: it is the structure that surrounds and limits the cell content.
- The nucleus: is the organelle that encloses the genetic material of the cell.
- The cytoplasm is the portion of the cell between the nucleus and the plasma membrane, where the rest of the organelles (mitochondria, ribosomes, vesicles, among others) and the aqueous medium where they float.
The eukaryotic cell is the hallmark of the Eukarya domain, where animals, fungi, plants, and protozoa are classified. Most eukaryotic cells are larger and more complex than prokaryotic cells, and can be found in unicellular (such as yeast) or multicellular (such as the earthworm) beings.
EUKARYOTIC CELL EXAMPLE
The Giardia lamblia is a single-celled protozoan, which is characterized by pear-shaped and four flagella that allow you to move. This parasite produces an intestinal infection characterized by abdominal pain and diarrhea.
Eukaryotic cell types
We can classify eukaryotic cells into two large groups: animal cell and plant cell.
The plant cell is characterized by having a plasma membrane, cell nucleus, and cytoplasm, where the organelles are found. It also has:
- Cell wall: a structure that covers the plasma membrane on the outside, composed mainly of cellulose fibers, which supports the cell.
- Chloroplasts: intracytoplasmic organelles with a double membrane, where the process of transforming solar energy into organic compounds is carried out by photosynthesis.
- Plasmodesmata: they are pores or passages that exist in the cell wall that allows the exchange of material between plant cells.
- Glioxisomes: are organelles found in the seeds, where the necessary lipids are stored and degraded in the germination process.
- Central vacuum: water storage area within the plant cell.
PLANT CELL EXAMPLE
Plant leaf cells, such as Elodea canadensis , are specialized to capture sunlight and absorb carbon dioxide from the air, for carbohydrate synthesis. All plants are autotrophic beings, that is, they are independent of other organisms to obtain their energy.
The animal cell is characterized by having a plasma membrane, cytoplasm, and nucleus, like the other eukaryotic cells. They are distinguished from plant cells in:
- They do not possess photosynthetic organelles or chloroplasts.
- Its cell membrane is composed of cholesterol, which is not found in plant cells.
- It has no cell wall.
- They have centrosomes, structures that have a role in the process of cell division.
ANIMAL CELL EXAMPLE
Within the diversity of animals that populate the Earth, one of the easiest cells to distinguish with the naked eye is eggs. Some have rigid protection coverage, such as bird eggs. Others are naked, as is the case with amphibian and fish eggs.
Main types of human cells
Within the human body, there is a great diversity of cells with specific functions.
Epithelial cells are found covering the outside of the body (in the skin) and internal surfaces (such as inside the mouth and nose). They can be flat, cubic or cylindrical, depending on the tissue they are part of. They are strongly linked to each other, without intercellular spaces. Its main function is to act as a protective barrier.
The fibroblast is the cell responsible for the formation and maintenance of connective tissue. They are also activated in the healing and wound repair processes. They are large, flattened and tapered, with an oval and flattened nucleus.
Adipocytes are lipid storage cells and are found in connective tissue and adipose tissue. They are very large and round, with a thin line of cytoplasm around a large fat vacuole.
Muscle cells are characterized mainly by their ability to contract. They are elongated in the direction of the movement they perform. They are found in skeletal muscle, heart muscle, and smooth muscle.
Monocytes and macrophages
Monocytes are cells of the immune system that develop in the bone marrow and are released into the blood. After a short period of time, the monocytes leave the blood vessels and penetrate the tissues, transforming into macrophages.
Red blood cells
Red blood cells, red blood cells or erythrocytes are characterized by being donut-shaped and being anucleated, because in the process of formation in the bone marrow, in the last stage of maturation, they lose the nucleus. Its main function is the exchange of gases:
- the transport of oxygen from the lungs to the tissues and
- the removal of carbon dioxide from the tissues to the lungs.
In the bones there are several types of cells:
- Osteoprogenitor cells appear in the fetal stage in the areas of bone growth;
- the osteoblasts are bone-forming cells;
- the osteocytes are cells maintaining bone quality;
- The osteoclasts are cells that degrade bone.
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