Comparative characteristics of cells of representatives of different kingdoms

Although the basic structural elements are similar in most cells, there are some differences in the structure of the cells of representatives of the different kingdoms of nature.

Plant cells:

• contain plastids characteristic only of them – chloroplasts, leukoplasts and chromoplasts;
• surrounded by a dense cellulose cell wall;
• have vacuoles with cell sap.

Vacuole is a single-membrane organoid that performs various functions (secretion, excretion and storage of reserve substances, autophagy, autolysis, etc.).

The shell of this vacuole is called tonoplast, and its contents are cell sap.

Plastids are plant cell organelles that have a two-membrane structure (like mitochondria). Like mitochondria, plastids contain their own DNA molecules. Therefore, they are also able to reproduce independently, regardless of cell division.

Depending on the color, plastids are divided into leukoplasts, chloroplasts and chromoplasts.

Leukoplasts are colorless and are usually found in non-illuminated parts of plants (for example, in potato tubers). They accumulate starch. In the light, the green pigment chlorophyll is formed in the leukoplasts, so the potato tubers turn green.

Chloroplasts are green plastids that are found in the cells of photosynthetic eukaryotes (plants). Typically, one cell of a plant leaf contains from 20 to 100 chloroplasts. Chloroplasts contain chlorophyll, and the process of photosynthesis takes place in them (that is, the conversion of the energy of sunlight into the energy of high-energy ATP bonds and the synthesis of carbohydrates from the carbon dioxide of the air due to this energy).

Under the outer smooth chloroplast membrane is a folded inner membrane. Between the folds of the inner membrane of the chloroplast are stacks (granules) of flat membrane sacs (thylakoids). The thylakoid membranes contain chlorophyll, which has a special chemical structure that allows it to capture light quanta.

Chlorophyll is essential for converting light energy into chemical energy ATP.

In the inner space of chloroplasts between the grains, carbohydrates are synthesized, which consumes ATP energy.

Chromoplasts contain pigments of red, orange, violet, yellow colors. These plastids are especially abundant in the cells of flower petals and fruit shells.
The main reserve substance of plant cells is starch.

Animal cells do not have dense cell walls. They are surrounded by a cell membrane through which metabolism with the environment takes place. The glycocalyx is located outside their plasma membrane.
Glycocalyx is a supramembrane complex characteristic of animal cells, which takes part in the formation of contacts between cells.

Also, there are no large vacoules in animal cells, but they have centrioles (in the cell center) and lysosomes.

The cell center takes part in cell division (centrioles diverge to the poles of the dividing cell and form a division spindle) and plays an important role in the formation of the internal skeleton of the cell – the cytoskeleton.

The cell center is located in the cytoplasm of all cells near the nucleus. From the area of ​​the cell center, numerous microtubules diverge, maintaining the shape of the cell and playing the role of a kind of rails for the movement of organelles through the cytoplasm.

In animals and lower plants, the cell center is formed by two centrioles (formed by microtubules located in the cytoplasm at right angles to each other).

In higher plants, the cell center does not have centrioles.

Lysosomes are organelles of fungi and animals that are absent in plant cells.

Lysosomes, possessing the ability to actively digest nutrients, are involved in the removal of cells, whole cells and organs dying off in the process of vital activity.

Sometimes lysosomes destroy the cell itself, in which they were formed.

Example: for example, lysosomes gradually digest all the cells of the tadpole’s tail when it turns into a frog. Thus, nutrients are not lost, but spent on the formation of new organs in the frog.

Organelles of movement. Many animal cells are capable of movement, for example, ciliates, green euglena, spermatozoa of multicellular animals. Some of these organisms move with the help of special organelles of movement – cilia and flagella, which are formed by the same microtubules as the centrioles of the cell center. The movement of flagella and cilia is caused by the sliding of microtubules relative to each other, as a result of which these organelles bend. At the base of each cilium or flagellum lies a basal body, which strengthens them in the cytoplasm of the cell. ATP energy is consumed for the work of flagella and cilia.

Fungal cells are covered with a cell wall that differs in chemical composition from the cell walls of plants. It contains chitin, polysaccharides, proteins and fats as the main components.