Cellular structure have all living organisms? Biology: the cellular structure of the organism

As is known, almost all organisms on our planet have a cellular structure. Basically, all cells have a similar structure. This is the smallest structural and functional unit of a living organism. Cells can have different functions, and, consequently, variations in their structure. In many cases, they can act as independent organisms. Cellular structure has plants, animals, fungi, bacteria. However, there are some differences between their structural-functional units. And in this article we will look at the cellular structure. Grade 8 provides for the study of this topic. Therefore, the article will be of interest to schoolchildren, as well as those who are simply interested in biology. This review will describe the cellular structure, cells of different organisms, similarities and differences between them.

History of the theory of cellular structure

People did not always know what organisms consist of. The fact that all tissues are formed from cells has become known relatively recently. The science that studies this is biology. The cell structure of the body was first described by scientists Matthias Schleiden and Theodore Schwann. It happened in 1838. Then the theory of the cellular structure consisted of such provisions:

• Animals and plants of all kinds are formed from cells;

• They grow through the formation of new cells;

• The cell is the smallest unit of life;

• An organism is a collection of cells.

Modern theory includes several different provisions, and a little more:

• The cell can only occur from the mother cell;

• A multicellular organism consists not of a simple set of cells, but of organs and systems of organs united in a tissue;

• Cells of all organisms have a similar structure;

• The cell is a complex system consisting of smaller functional units;

• The cell is the smallest structural unit capable of acting as an independent organism.

Cell structure

Since the cellular structure has almost all living organisms, it is worth considering a general characteristic of the structure of this element. First, all cells are divided into prokaryotic and eukaryotic. In the latter, there is a nucleus that protects hereditary information recorded on DNA. In prokaryotic cells it is absent, and DNA freely floats. All eukaryotic cells are constructed according to the following scheme. They have a membrane - a plasma membrane, around which additional protective structures are usually located. Everything that is under it, except the nucleus, is the cytoplasm. It consists of hyaloplasm, organoids and inclusions. Hyaloplasma is the basic transparent substance that serves as the internal environment of the cell and fills all of its space. Organoids are permanent structures that perform certain functions, that is, they ensure the vital activity of the cell. Inclusions are non-permanent entities that also play a role, but they do it temporarily.

Cellular structure of living organisms

Now we list the organoids that are the same for the cells of any living creature on the planet, other than bacteria. These are mitochondria, ribosomes, Golgi apparatus, endoplasmic reticulum, lysosomes, cytoskeleton. For bacteria, only one of these organoids, the ribosomes, is characteristic. Now consider the structure and functions of each organelle separately.

Mitochondria

They provide intracellular respiration. Mitochondria play the role of a kind of "power station", generating the energy that is necessary for the life of the cell, for the passage in it of certain chemical reactions. They belong to the two-membrane organoids, that is, they have two protective shells - external and internal. Under them is a matrix - an analog of the hyaloplasm in the cell. Between the outer and inner membranes, cristae form. These are the folds inside which the enzymes are located. These substances are needed in order to be able to carry out chemical reactions, due to which the energy necessary for the cell is released.

Ribosomes

They are responsible for the protein metabolism, namely - for the synthesis of substances of this class. Ribosomes consist of two parts - subunits, large and small. The membrane of this organoid is absent. Subunits of ribosomes are combined only immediately before the process of protein synthesis, at the rest of the time they are separated. The substances here are produced on the basis of information recorded on DNA. This information is delivered to the ribosomes using tRNA, since transporting DNA here every time would be very impractical and dangerous - the likelihood of damage would be too high.

Apparatus Golgi

This organoid consists of stacks of flat tanks. The functions of this organoid are that it accumulates and modifies various substances, and also participates in the process of formation of lysosomes.

Endoplasmic reticulum

It is subdivided into a smooth and rough. The first is built of flat tubules. He is responsible for the production of steroids and lipids in the cell. Roughness is called so because on the walls of the membranes, of which it consists, are numerous ribosomes. He performs the transport function. Namely, it transfers from the ribosomes the proteins synthesized there to the Golgi apparatus.

Lysosomes

They are single-membrane organoids, which contain enzymes necessary for the realization of chemical reactions that occur in the process of intracellular metabolism. The greatest amount of lysosomes is observed in leukocytes - cells performing immune function. This is explained by the fact that they carry out phagocytosis and are forced to digest a foreign protein, which requires a large volume of enzymes.

Cytoskeleton

This is the last organelle, which is common for mushrooms, animals and plants. One of its main functions is to maintain the shape of the cell. It is formed from microtubules and microfilaments. The first are hollow tubes of tubulin protein. Due to their presence in the cytoplasm some organelles can move around the cell. In addition, microtubules can also consist of cilia and flagella in unicellular organisms. The second component of the cytoskeleton - microfilaments - consists of the contractile proteins actin and myosin. In bacteria, this organelle is usually absent. But some of them are characterized by the presence of a cytoskeleton, but more primitive, arranged not so hard as in fungi, plants and animals.

Organa of plant cells

Cellular structure of plants has some features. In addition to the organelles listed above, vacuoles and plastids are also present. The first are intended for the accumulation of substances in it, including unnecessary ones, since it is often impossible to remove them from the cell due to the presence of a dense wall around the membrane. The fluid that is inside the vacuole is called the cell sap. In a young plant cell, there are initially a few small vacuoles, which, as they age, merge into one large vacuole. Plastids are divided into three types: chromoplasts, leukoplasts and chromoplasts. The former are characterized by the presence of a red, yellow or orange pigment in them. Chromoplasts are in most cases needed to attract the bright color of pollinating insects or animals that participate in the spread of fruits along with the seeds. It is thanks to these organoids that flowers and fruits have a variety of colors. Chromoplasts can be formed from chloroplasts, which can be observed in the autumn, when the leaves acquire yellow-red shades, as well as when the fruit ripens, when the green color gradually disappears. The next kind of plastids - leukoplasts - are designed to store substances such as starch, some fats and proteins. Chloroplasts carry out the process of photosynthesis, due to which plants receive for themselves the necessary organic substances. Of the six molecules of carbon dioxide and so much water, the cell can get one molecule of glucose and six oxygen that is released into the atmosphere. Chloroplasts are two-membrane organoids. Their matrix contains thylakoids grouped in granules. In these structures, and contains chlorophyll, here the photosynthetic reaction proceeds. In addition, the matrix of chloroplasts also contains its ribosomes, RNA, DNA, special enzymes, starch grains and lipid droplets. The matrix of these organoids is also called the stroma.

Features of mushrooms

Cellular structure also has these organisms. In antiquity they were united in one kingdom with plants purely on an external basis, however, with the advent of a more developed science, it turned out that this can not be done at all. Firstly, fungi, unlike plants, are not autotrophs, they are not able to produce organic substances themselves, but only eat ready-made ones. Secondly, the cell of the fungus is more similar to the animal, although it has some features of plant. The mushroom cell, like plants, is surrounded by a dense wall, but it consists not of cellulose, but of chitin. This substance is difficult to digest by the body of animals, so fungi and are considered a serious food. In addition to the organelles described above, which are characteristic of all eukaryotes, there is also a vacuole - here is another similarity between fungi and plants. But plastids are not observed in the structure of the fungal cell. Between the wall and the cytoplasmic membrane is a lomasome, the functions of which have not yet been fully studied. In other respects, the structure of the fungal cell resembles an animal. In addition to organelles, in the cytoplasm such inclusions as the fat drops, glycogen also float.

Animal cells

They are characterized by all the organelles that were described at the beginning of the article. In addition, on top of the plasma membrane is located glycocalyx - a shell consisting of lipids, polysaccharides and glycoproteins. It participates in the transport of substances between cells.

Core

Of course, in addition to common organelles, there is a nucleus in animals, plant cells, and fungal cells. It is protected by two shells, in which there are pores. The matrix consists of a karyoplasm (nuclear juice) in which chromosomes float with the hereditary information recorded on them. There are also nucleoli, which are responsible for the formation of ribosomes and the synthesis of RNA.

Prokaryotes

These include bacteria. Cellular structure of bacteria is more primitive. They do not have a kernel. The cytoplasm contains such organoids as ribosomes. A cell wall of murein is located around the plasma membrane. Most prokaryotes are equipped with movement organoids - mostly flagella. An additional protective shell can also be located around the cell wall - the mucous capsule. In addition to the main DNA molecules, in the cytoplasm of bacteria there are plasmids on which information is recorded that is responsible for increasing the body's resistance to unfavorable conditions.

Are all organisms built from cells?

Some believe that the cellular structure has all living organisms. But this is not true. There is such a kingdom of living organisms as viruses. They do not consist of cells. This organism is represented by a capsid - a protein coat. Inside it is DNA or RNA, on which a small amount of genetic information is recorded. Around the protein membrane, lipoprotein may also be located, which is called supercapsid. Viruses can multiply only inside other people's cells. In addition, they are capable of crystallization. As you can see, the assertion that the cellular structure has all living organisms is wrong.

comparison table

After we have examined the structure of various organisms, let us summarize. So, the cellular structure, the table:

Here, perhaps, that's all. We examined the cellular structure of all organisms that exist on the planet.