A plant cell differs from an animal cell. How is a plant cell different from an animal cell?

2. The main chemical components of protoplast. Organic substances of the cell. Proteins - biopolymers formed by amino acids, make up 40-50% of the dry mass of the protoplast. They participate in building the structure and functions of all organelles. Chemically, proteins are divided into simple (proteins) and complex (proteids). Complex proteins can form complexes with lipids - lipoproteins, with carbohydrates - glycoproteins, with nucleic acids - nucleoproteins, etc.

Proteins are part of enzymes that regulate all vital processes.

Cytoplasm is a thick transparent colloidal solution. Depending on the performed physiological functions each cell has its own chemical composition. The basis of the cytoplasm is its hyaloplasm, or matrix, the role of which is to unite all cellular structures into a single system and ensure interaction between them. The cytoplasm has an alkaline reaction of the environment and consists of 60-90% water in which various substances are dissolved: up to 10-20% proteins, 2-3% fat-like substances, 1.5% organic and 2-3% inorganic compounds. The most important physiological process occurs in the cytoplasm - respiration, or glycolysis, as a result of which glucose is broken down without oxygen in the presence of enzymes, releasing energy and producing water and carbon dioxide.

The cytoplasm is permeated with membranes - thin films of phospholipid structure. The membranes form the endoplasmic reticulum - a system of small tubules and cavities that form a network. The endoplasmic reticulum is called rough (granular) if the membranes of the tubules and cavities contain ribosomes or groups of ribosomes that perform protein synthesis. If the endoplasmic reticulum is devoid of ribosomes, it is called smooth (agranular). Lipids and carbohydrates are synthesized on the membranes of the smooth endoplasmic reticulum.

The Golgi apparatus is a system of flattened cisterns lying parallel and bounded by double membranes. From the ends of the tanks, vesicles are detached, through which the final or toxic products of the cell's vital activity are removed, and the substances necessary for the synthesis of complex carbohydrates (polysaccharides) for the construction of the cell wall are supplied back to the dictyosomes. The Golgi complex is also involved in the formation of vacuoles. One of the most important biological properties of the cytoplasm is cyclosis (the ability to move), the intensity of which depends on temperature, degree of illumination, oxygen supply and other factors.

Ribosomes are tiny particles (from 17 to 23 nm) formed by ribonucleoproteins and protein molecules. They are present in the cytoplasm, nucleus, mitochondria, plastids; There are single and group (polysomes). Ribosomes are centers of protein synthesis.

Mitochondria are the “energy stations” of all eukaryotic cells. Their shape is varied: from round to cylindrical and even rod-shaped bodies. Their number ranges from several tens to several thousand in each cell. Dimensions no more than 1 micron. On the outside, mitochondria are surrounded by a double-membrane membrane. The inner membrane is presented in the form of lamellar outgrowths - cristae. They reproduce by division.

The main function of mitochondria is to participate in cell respiration with the help of enzymes. In mitochondria, energy-rich molecules of adenosine triphosphoric acid (ATP) are synthesized as a result of oxidative phosphorylation. The mechanism of oxidative phosphorylation was discovered by the English biochemist P. Mitchell in 1960.

Plastids. These organelles, unique to plants, are found in all living plant cells. Plastids are relatively large (4-10 microns) living plant bodies different shapes and coloring. There are three types of plastids: 1) chloroplasts, colored green; 2) chromoplasts, colored yellow-red; 3) leucoplasts that do not have color.

Chloroplasts are found in all green plant organs. In higher plants there are several dozen plastids in the cells, in lower plants (algae) - 1-5. They are large and varied in shape. Chloroplasts contain up to 75% water, proteins, lipids, nucleic acids, enzymes and dyes - pigments. For the formation of chlorophyll, certain conditions are necessary - light, iron and magnesium salts in the soil. The chloroplast is separated from the cytoplasm by a double membrane membrane; its body consists of colorless fine-grained stroma. The stroma is penetrated by parallel plates - lamellae, discs. The discs are collected in stacks - grana. The main function of chloroplasts is photosynthesis.

Chromoplasts are found in carrot roots, fruits of many plants (sea buckthorn, rose hips, rowan, etc.), in green leaves of spinach, nettles, in flowers (roses, gladioli, calendula), the color of which depends on the presence of carotenoid pigments in them: carotene - orange - red and xanthophyll - yellow.

Leucoplasts are colorless plastids with no pigments. They are protein substances in the form of spherical, spindle-shaped grains concentrated around the core. They carry out the synthesis and accumulation of reserve nutrients, mainly starch, proteins and fats. Leukoplasts are found in the cytoplasm, epidermis, young hairs, underground organs of plants and in the tissues of the seed embryo.

Plastids can change from one type to another.

Core.

The nucleus is one of the main organelles of a eukaryotic cell. A plant cell has one nucleus. Hereditary information is stored and reproduced in the nucleus. The size of the kernel varies from plant to plant, from 2-3 to 500 microns. The shape is often round or lenticular. In young cells, the nucleus is larger than in old cells and occupies a central position. The core is surrounded by a double membrane with pores that regulate metabolism. The outer membrane is integrated with the endoplasmic reticulum. Inside the nucleus is nuclear juice - karyoplasm with chromatin, nucleoli and ribosomes. Chromatin is a structureless medium of special nucleoprotein threads rich in enzymes.

The bulk of DNA is concentrated in chromatin. In progress cell division Chromatin turns into chromosomes - gene carriers. Chromosomes are formed by two identical strands of DNA - chromatids. Each chromosome has a constriction in the middle - a centromere. The number of chromosomes varies from plant to plant: from two to several hundred. Each plant species has a constant set of chromosomes. Chromosomes synthesize nucleic acids necessary for the formation of proteins. The set of quantitative and qualitative characteristics of the chromosome set of a cell is called a karyotype. Changes in the number of chromosomes occur as a result of mutations. The hereditary multiple increase in the number of chromosomes in plants is called polyploidy.

The nucleoli are spherical, rather dense bodies with a diameter of 1-3 microns. The nucleus contains 1-2, sometimes several nucleoli. The nucleolus is the main carrier of RNA in the nucleus. The main function of the nucleolus is rRNA synthesis.

Division of nucleus and cell. Cell reproduction occurs through cell division. The period between two successive divisions constitutes the cell cycle. When cells divide, the plant grows and its total mass increases. There are three ways of cell division: mitosis, or karyokinesis (indirect division), meiosis (reduction division) and amitosis (direct division).

Mitosis is characteristic of all cells of plant organs, except sex cells. As a result of mitosis, the total mass of the plant grows and increases. The biological significance of mitosis lies in the strictly identical distribution of reduplicated chromosomes between daughter cells, which ensures the formation of genetically equivalent cells. Mitosis was first described by the Russian botanist I.D. Chistyakov in 1874. In the process of mitosis, several phases are distinguished: prophase, metaphase, anaphase and telophase. The interval between two cell divisions is called interphase. In interphase, general cell growth, reduplication of organelles, DNA synthesis, formation and preparation of structures for the beginning of mitotic division take place.

Prophase is the longest phase of mitosis. During prophase, chromosomes become visible under a light microscope. In prophase, the nucleus undergoes two changes: 1. the dense coil stage; 2. loose ball stage. At the dense coil stage, the chromosomes become visible under a light microscope, unwind from the coil or spiral, and stretch out. Each chromosome consists of two chromatids located parallel to each other. Gradually they shorten, thicken and separate, the nuclear membrane and nucleolus disappear. The nucleus increases in volume. At the opposite poles of the cell, an achromatin spindle is formed - a fission spindle, consisting of non-staining threads extending from the poles of the cell (loose ball stage).

In metaphase, the formation of the division spindle ends, the chromosomes acquire a certain shape of a particular plant species and are assembled in one plane - the equatorial one, in the place of the former nucleus. The achromatin spindle gradually contracts, and the chromatids begin to separate from each other, remaining connected at the centromere.

In anaphase, the centromere divides. The resulting sister centromeres and chromatids are directed to opposite poles of the cell. Independent chromatids become daughter chromosomes, and, therefore, there will be exactly as many of them as in the mother cell.

Telophase is the last phase of cell division, when the daughter chromosomes reach the cell poles, the division spindle gradually disappears, the chromosomes elongate and become difficult to see in a light microscope, and a median plate is formed in the equatorial plane. Gradually, a cell wall is formed and, at the same time, nucleoli and a nuclear envelope around two new nuclei (1. stage of a loose ball; 2. stage of a dense ball). The resulting cells enter the next interphase.

The duration of mitosis is approximately 1-2 hours. The process from the moment of formation of the median plate to the formation new cell called cytokinesis. Daughter cells are twice as small as the mother cells, but then they grow and reach the size of the mother cell.

Meiosis. It was first discovered by the Russian botanist V.I. Belyaev in 1885. This type of cell division is associated with the formation of spores and gametes, or germ cells with a haploid number of chromosomes (n). Its essence lies in reducing (reducing) the number of chromosomes by 2 times in each cell formed after division. Meiosis consists of two successive divisions. Meiosis, unlike mitosis, consists of two types of division: reduction (increase); equatorial (mitotic division). Reduction division occurs during the first division, which consists of several phases: prophase I, metaphase I, anaphase I, telophase I. In equatorial division there are: prophase II, metaphase II, anaphase II, telophase II. In reduction division there is an interphase.

Prophase I. Chromosomes are shaped like long double strands. A chromosome consists of two chromatids. This is the leptonema stage. Then homologous chromosomes are attracted to each other, forming pairs - bivalents. This stage is called zygonema. Paired homologous chromosomes consist of four chromatids, or tetrads. Chromatids can be located parallel to each other or intersect with each other, exchanging sections of chromosomes. This stage is called crossing over. In the next stage of prophase I - pachynema, the chromosomal strands thicken. In the next stage, diplonema, the chromatid tetrads are shortened. The conjugating chromosomes move closer to each other so that they become indistinguishable. The nucleolus and nuclear envelope disappear, and the achromatin spindle is formed. In the last stage - diakinesis - the bivalents are directed towards the equatorial plane.

Metaphase I. Bivalents are located along the equator of the cell. Each chromosome is attached by an achromatin spindle to the centromere.

Anaphase I. The filaments of the achromatin spindle contract, and homologous chromosomes in each bivalent diverge to opposite poles, and at each pole there will be half the number of chromosomes of the mother cell, i.e. the number of chromosomes decreases (reduction) and two haploid nuclei are formed.

Telophase I. This phase is weakly expressed. Chromosomes decondense; the nucleus takes on an interphase appearance, but chromosome doubling does not occur in it. This stage is called interkinesis. It is short-lived, absent in some species, and then the cells immediately after telophase I enter prophase II.

The second meiotic division occurs as mitosis.

Prophase II. It occurs quickly, following telophase I. There are no visible changes in the nucleus and the essence of this stage is that the nuclear membranes are reabsorbed and four division poles appear. Two poles appear near each nucleus.

Metaphase II. The duplicated chromosomes line up at their equators and the stage is called the mother star or equatorial plate stage. Spindle threads extend from each division pole and attach to the chromatids.

Anaphase II. The division poles stretch the filaments of the spindle, which begin to dissolve and stretch the doubled chromosomes. There comes a moment of chromosome breakage and their divergence to the four poles.

Telophase II. Around each pole of the chromosomes there is a loose coil stage and a dense coil stage. After which the centrioles dissolve and nuclear membranes and nucleoli are restored around the chromosomes. After which the cytoplasm divides.

The result of meiosis is the formation of four daughter cells from one mother cell with a haploid set of chromosomes.

Each plant species is characterized by a constant number of chromosomes and a constant shape. Among higher plants, the phenomenon of polyploidy is often encountered, i.e. repetition in the nucleus of one set of chromosomes (triploids, tetraploids, etc.).

In old and diseased plant cells, direct (amitosis) division of the nucleus can be observed by simply constricting it into two parts with an arbitrary amount of nuclear matter. This division was first described by N. Zheleznov in 1840.

Protoplast derivatives.

Protoplast derivatives include:

1) vacuoles;

2) inclusions;

3) cell wall;

4) physiologically active substances: enzymes, vitamins, phytohormones, etc.;

5) metabolic products.

Vacuoles - cavities in the protoplast - derivatives of the endoplasmic reticulum. They are bounded by a membrane - the tonoplast and filled with cell sap. Cell sap accumulates in the channels of the endoplasmic reticulum in the form of droplets, which then merge to form vacuoles. Young cells contain many small vacuoles; old cells usually contain one large vacuole. Sugars (glucose, fructose, sucrose, inulin), soluble proteins, organic acids (oxalic, malic, citric, tartaric, formic, acetic, etc.), various glycosides, tannins, alkaloids (atropine, papaverine, morphine) are dissolved in the cell sap etc.), enzymes, vitamins, phytoncides, etc. The cell sap of many plants contains pigments - anthocyanin (red, blue, purple in different shades), anthochlores (yellow), antopheines (dark brown). Seed vacuoles contain protein proteins. Many inorganic compounds are also dissolved in cell sap.

Vacuoles are places where metabolic end products are deposited.

Vacuoles form the internal aqueous environment of the cell, with their help the regulation of water-salt metabolism is carried out. Vacuoles maintain turgor hydrostatic pressure inside cells, which helps maintain the shape of non-lignified parts of plants - leaves, flowers. Turgor pressure is associated with the selective permeability of the tonoplast for water and the phenomenon of osmosis - one-sided diffusion of water through a semi-permeable partition towards an aqueous solution of salts of higher concentration. The water entering the cell sap exerts pressure on the cytoplasm, and through it on the cell wall, causing its elastic state, i.e. providing turgor. Lack of water in the cell leads to plasmolysis, i.e. to a reduction in the volume of vacuoles and separation of protoplasts from the shell. Plasmolysis can be reversible.

Inclusions are substances formed as a result of the life of a cell, either in reserve or as waste. Inclusions are localized either in the hyaloplasm and organelles, or in the vacuole in a solid or liquid state. Inclusions are reserve nutrients, for example, starch grains in potato tubers, bulbs, rhizomes and other plant organs, deposited in a special type of leucoplasts - amyloplasts.

The cell wall is a solid structure that gives each cell its shape and strength. It plays a protective role, protecting the cell from deformation and resists high osmotic pressure large central vacuole and prevents cell rupture. The cell wall is a product of the vital activity of the protoplast. The primary cell wall is formed immediately after cell division and consists mainly of pectin substances and cellulose. As it grows, it becomes rounded, forming intercellular spaces filled with water, air or pectin substances. When the protoplast dies, the dead cell is able to conduct water and perform its mechanical role.

The cell wall can only grow in thickness. On inner surface After the primary cell wall, the secondary cell wall begins to be deposited. Thickening can be internal or external. External thickenings are possible only on the free surface, for example, in the form of spines, tubercles and other formations (spores, pollen grains). The internal thickening is represented by sculptural thickenings in the form of rings, spirals, vessels, etc. Only the pores - places in the secondary cell wall - remain unthickened. Through the pores along plasmodesmata - strands of cytoplasm - the exchange of substances between cells occurs, irritation is transmitted from one cell to another, etc. Pores can be simple or bordered. Simple pores are found in parenchymal and prosenchymal cells, bordered by vessels and tracheids that conduct water and minerals.

The secondary cell wall is built mainly from cellulose, or fiber (C 6 H 10 O 5) n - a very stable substance, insoluble in water, acids and alkalis.

With age, cell walls undergo modifications and are impregnated with various substances. Types of modifications: suberization, lignification, cutinization, mineralization and mucilage. Thus, during suberization, the cell walls are impregnated with a special substance suberin, during lignification - with lignin, during cutinization - with the fat-like substance cutin, during mineralization - with mineral salts, most often calcium carbonate and silica; during mucusification, the cell walls absorb a large amount of water and swell greatly.

Enzymes, vitamins, phytohormones. Enzymes are organic catalysts of a protein nature and are present in all organelles and cell components.

Vitamins are organic substances of different chemical compositions that are present as components in enzymes and act as catalysts. Vitamins are designated by capital letters of the Latin alphabet: A, B, C, D, etc. There are water-soluble vitamins (B, C, PP, H, etc.) and fat-soluble (A, D, E).

Water-soluble vitamins are found in cell sap, and fat-soluble vitamins are found in the cytoplasm. More than 40 vitamins are known.

Phytohormones are physiologically active substances. The most studied growth hormones are auxin and gibberellin.

Flagella and cilia. Flagella are motor devices in prokaryotes and in most lower plants.

Many algae and male reproductive cells of higher plants have cilia, with the exception of angiosperms and some gymnosperms.

Plant tissue

1. General characteristics and classification of fabrics.

2. Educational tissues.

3. Integumentary tissues.

4. Basic fabrics.

5. Mechanical fabrics.

6. Conductive fabrics.

7. Excretory tissues.

The concept of tissues as groups of similar cells appeared already in the works of the first botanist-anatomists in the 17th century. Malpighi and Grew described the most important tissues, in particular, they introduced the concepts of parenchyma and prosenchyma.

The classification of tissues based on physiological functions was developed in the late 19th and early 20th centuries. Schwendener and Haberlandt.

Tissues are groups of cells that have a homogeneous structure, the same origin and perform the same function.

Depending on the function performed, the following types of tissues are distinguished: educational (meristems), basic, conductive, integumentary, mechanical, excretory. Cells that make up a tissue and have more or less the same structure and functions are called simple; if the cells are not the same, then the tissue is called complex or complex.

Tissues are divided into educational, or meristem, and permanent (integumentary, conductive, basic, etc.).

Classification of fabrics.

1. Educational tissues (meristems):

1) apical;

2) lateral: a) primary (procambium, pericycle);

b) secondary (cambium, phellogen)

3) insertion;

4) wounded.

2. Basic:

1) assimilation parenchyma;

2) storage parenchyma.

3. Conductive:

1) xylem (wood);

2) phloem (bast).

4. Integumentary (borderline):

1) external: a) primary (epidermis);

b) secondary (periderm);

c) tertiary (crust, or rhytide)

2) external: a) rhizoderm;

b) velamen

3) internal: a) endoderm;

b) exodermis;

c) parietal cells of vascular bundles in leaves

5. Mechanical (supporting, skeletal) tissues:

1) collenchyma;

2) sclerenchyma:

a) fibers;

b) sclereids

6. Excretory tissues (secretory).

2. Educational tissues. Educational tissues, or meristems, are constantly young, actively dividing groups of cells. They are located in places where various organs grow: the tips of roots, the tops of stems, etc. Thanks to meristems, plant growth and the formation of new permanent tissues and organs occur.

Depending on the location in the plant body, the educational tissue can be apical or apical, lateral or lateral, intercalary or intercalary, and wound. Educational tissues are divided into primary and secondary. Thus, apical meristems are always primary; they determine the length of the plant. In low-organized higher plants (horsetails, some ferns), the apical meristems are weakly expressed and are represented by only one initial, or initial dividing cell. In gymnosperms and angiosperms, the apical meristems are well defined and are represented by many initial cells forming growth cones.

Lateral meristems, as a rule, are secondary and due to them the axial organs (stems, roots) grow in thickness. The lateral meristems include the cambium and cork cambium (phellogen), the activity of which contributes to the formation of cork in the roots and stems of the plant, as well as a special aeration tissue - lentils. The lateral meristem, like the cambium, forms wood and bast cells. During unfavorable periods of a plant’s life, the activity of the cambium slows down or stops altogether. Intercalary, or intercalary, meristems are most often primary and are preserved in the form of separate sections in zones of active growth, for example, at the base of internodes and at the base of petioles of cereal leaves.

3. Integumentary tissues. Cover tissues protect the plant from adverse environmental influences: solar overheating, excessive evaporation, sudden changes in air temperature, drying wind, mechanical impact, from the penetration of pathogenic fungi and bacteria into the plant, etc. There are primary and secondary integumentary tissues. Primary integumentary tissues include the skin, or epidermis, and epiblema, and secondary tissues include the periderm (cork, cork cambium and phelloderm).

The skin, or epidermis, covers all organs of annual plants, young green shoots of perennial woody plants of the current growing season, and above-ground herbaceous parts of plants (leaves, stems and flowers). The epidermis most often consists of a single layer of tightly packed cells without intercellular space. It is easily removable and is a thin transparent film. The epidermis is a living tissue, consisting of a gradual layer of protoplast with leukoplasts and a nucleus, a large vacuole occupying almost the entire cell. The cell wall is mainly cellulose. The outer wall of the epidermal cells is thicker, the lateral and internal ones are thin. The side and inner walls of the cells have pores. The main function of the epidermis is the regulation of gas exchange and transpiration, carried out mainly through the stomata. Water and inorganic substances penetrate through the pores.

Epidermal cells of different plants are not the same in shape and size. In many monocotyledonous plants, the cells are elongated; in most dicotyledonous plants, they have sinuous side walls, which increases the density of their adhesion to each other. Epidermis of the upper and lower parts the leaf also differs in its structure: on the underside of the leaf in the epidermis there are a larger number of stomata, and on the upper side there are much fewer of them; on the leaves of aquatic plants with leaves floating on the surface (water lily, water lily), stomata are present only on the upper side of the leaf, and in plants completely submerged in water there are no stomata.

Stomata are highly specialized formations of the epidermis, consisting of two guard cells and a slit-like formation between them - the stomatal fissure. Crescent-shaped guard cells regulate the size of the stomatal fissure; the gap can open and close depending on the turgor pressure in the guard cells, the carbon dioxide content in the atmosphere and other factors. Thus, during the day, when stomatal cells participate in photosynthesis, the turgor pressure in the stomatal cells is high, the stomatal fissure is open, and at night, on the contrary, it is closed. Similar phenomenon observed in dry times and when leaves wither, it is associated with the adaptation of stomata to store moisture inside the plant. Many species that grow in wet areas, especially tropical rainforests, have stomata through which water is released. The stomata are called hydathodes. Water in the form of droplets is released out and drips from the leaves. The “crying” of a plant is a kind of weather predictor and is scientifically called guttation. Hydathodes are located along the edge of the leaf; they do not have an opening or closing mechanism.

The epidermis of many plants has protective devices against unfavorable conditions: hairs, cuticle, waxy coating, etc.

Hairs (trichomes) are peculiar outgrowths of the epidermis; they can cover the entire plant or some of its parts. Hairs can be living or dead. The hairs help reduce moisture evaporation, protect the plant from overheating, being eaten by animals, and from sudden temperature fluctuations. Therefore, plants in arid - arid regions, high mountains, and subpolar regions of the globe, as well as plants in weedy habitats, are most often covered with hairs.

Hairs are unicellular and multicellular. Single-celled hairs are presented in the form of papillae. Papillae are found on the petals of many flowers, giving them a velvety feel (tagetis, pansy). Single-celled hairs may be simple (on the underside of many fruit crops) and are usually dead. Single-celled hairs can be branched ( shepherd's purse). More often, the hairs are multicellular, differing in structure: linear (potato leaves), bushy-branched (mullein), scaly and stellate-squamous (representatives of the Sucker family), massive (tufts of hairs from plants of the Lamiaceae family). There are glandular hairs in which they can accumulate essential substances(labiaceae and umbelliferous plants), stinging substances (nettle), etc. Stinging nettle hairs, thorns of roses, blackberries, thorns on the fruits of umbellifers, datura, chestnut, etc. are peculiar outgrowths called emergents, in the formation of which they take part in addition to epidermal cells deeper layers of cells.

Epiblema (rhizoderm) is the primary single-layer integumentary tissue of the root. It is formed from the outer cells of the apical meristem of the root near the root cap. The epiblema covers the young root endings. Through it, water and mineral nutrition of the plant from the soil is carried out. There are many mitochondria in the epiblema. Epiblema cells are thin-walled, with more viscous cytoplasm, and lack stomata and cuticle. The epiblema is short-lived and is constantly renewed through mitotic divisions.

Periderm is a complex multilayer complex of secondary integumentary tissue (cork, cork cambium, or phellogen, and phelloderm) of the stems and roots of perennial dicotyledonous plants and gymnosperms, which are capable of continuously thickening. By the autumn of the first year of life, the shoots become lignified, which is noticeable by a change in their color from green to brown-gray, i.e. There was a change from the epidermis to the periderm, which could withstand the unfavorable conditions of the winter period. The periderm is based on a secondary meristem - phellogen (cork cambium), formed in the cells of the main parenchyma lying under the epidermis.

Phellogen forms cells in two directions: outward - cork cells, inward - living phelloderm cells. The cork consists of dead cells filled with air, they are elongated, tightly adjacent to each other, there are no pores, the cells are air- and water-tight. Cork cells have a brown or yellowish color, which depends on the presence of resinous or tannin substances in the cells (cork oak, Sakhalin velvet). Cork is a good insulating material, does not conduct heat, electricity or sound, and is used to seal bottles, etc. A thick layer of cork has cork oak, types of velvet, and cork elm.

Lentils are “ventilation” holes in the plug to ensure gas and water exchange of living, deeper plant tissues with the external environment. Externally, lentils are similar to lentil seeds, which is why they got their name. As a rule, lenticels are laid to replace stomata. The shapes and sizes of lentils are different. Quantitatively, there are much fewer lenticels than stomata. Lentils are round, thin-walled, chlorophyll-free cells with intercellular spaces that lift the skin and break it. This layer of loose, slightly suberized parenchyma cells that make up the lentil is called fulfilling tissue.

The crust is a powerful integumentary complex of dead outer cells of the periderm. It forms on perennial shoots and roots of woody plants. The crust has a cracked and uneven shape. It protects tree trunks from mechanical damage, ground fires, low temperatures, sunburn, penetration pathogenic bacteria and mushrooms. The crust grows due to the growth of new layers of periderm underneath it. In tree and shrub plants, the crust appears (for example, in pine) in the 8-10th year, and in oak - in the 25-30th year of life. The bark is part of the bark of trees. On the outside, it constantly peels off, throwing off all kinds of spores of fungi and lichens.

4. Basic fabrics. The ground tissue, or parenchyma, occupies most of the space between other tissues permanent tissues stems, roots and other plant organs. Basic tissues consist mainly of living cells, varying in shape. The cells are thin-walled, but sometimes thickened and lignified, with walled cytoplasm and simple pores. Parenchyma consists of the bark of stems and roots, the core of stems, rhizomes, the pulp of juicy fruits and leaves; it serves as a storage facility for nutrients in the seeds. There are several subgroups of basic tissues: assimilation, storage, aquifer and pneumatic.

Assimilation tissue, or chlorophyll-bearing parenchyma, or chlorenchyma, is the tissue in which photosynthesis occurs. The cells are thin-walled, contain chloroplasts and a nucleus. Chloroplasts, like the cytoplasm, are arranged wall-to-wall. Chlorenchyma is located directly under the skin. Chlorenchyma is mainly concentrated in the leaves and young green shoots of plants. The leaves are distinguished between palisade, or columnar, and spongy chlorenchyma. The cells of palisade chlorenchyma are elongated, cylindrical in shape, with very narrow intercellular spaces. Spongy chlorenchyma has more or less rounded, loosely arranged cells with a large number of intercellular spaces filled with air.

Aerenchyma, or pneumatic tissue, is parenchyma with significantly developed intercellular spaces in different organs is typical for aquatic, coastal-aquatic and marsh plants (reeds, rushes, egg capsules, pondweeds, water plants, etc.), the roots and rhizomes of which are located in silt, poor in oxygen. Atmospheric air reaches underwater organs through the photosynthetic system through transmitting cells. In addition, air-bearing intercellular spaces communicate with the atmosphere through peculiar pneumatodes - stomata of leaves and stems, pneumatodes of aerial roots of some plants (Monstera, philodendron, ficus banyan, etc.), cracks, holes, channels surrounded by communication regulator cells. Aerenchyma reduces specific gravity plants, which probably helps to maintain the vertical position of aquatic plants, and for aquatic plants with leaves floating on the surface of the water - to keep the leaves on the surface of the water.

Aquiferous tissue stores water in the leaves and stems of succulent plants (cacti, aloe, agaves, crassula, etc.), as well as plants of saline habitats (soleros, biyurgun, sarsazan, saltwort, comb grass, black saxaul, etc.), usually in arid areas. The leaves of cereals also have large water-bearing cells with mucous substances that retain moisture. Sphagnum moss has well-developed aquifer cells.

Storage fabrics - tissues in which, at a certain period of plant development, they deposit metabolic products - proteins, carbohydrates, fats, etc. The cells of the storage tissue are usually thin-walled, the parenchyma is living. Storage tissues are widely represented in tubers, bulbs, thickened roots, the core of stems, endosperm and seed embryos, parenchyma of conducting tissues (beans, aroids), reservoirs of resins and essential oils in the leaves of laurel, camphor tree, etc. Storage tissue can turn into chlorenchyma, for example, during the germination of potato tubers and bulbs of bulbous plants.

5. Mechanical fabrics. Mechanical or supporting tissues - This is a kind of armature, or stereo. The term stereom comes from the Greek “stereos” - solid, durable. The main function is to provide resistance to static and dynamic loads. In accordance with their functions, they have an appropriate structure. In terrestrial plants they are most developed in the axial part of the shoot - the stem. Cells of mechanical tissue can be located in the stem either along the periphery, or in a continuous cylinder, or in separate areas in the edges of the stem. In the root, which bears mostly tensile strength, the mechanical tissue is concentrated in the center. The structural feature of these cells is the strong thickening of the cell walls, which give the tissues strength. Mechanical tissues are the most well developed in woody plants. Based on the structure of cells and the nature of thickening of cell walls, mechanical tissues are divided into two types: collenchyma and sclerenchyma.

Collenchyma is a simple primary supporting tissue with living cell contents: nucleus, cytoplasm, sometimes with chloroplasts, with unevenly thickened cell walls. Based on the nature of the thickenings and the connection of cells with each other, three types of collenchyma are distinguished: angular, lamellar and loose. If the cells are thickened only at the corners, then this is angular collenchyma, and if the walls are thickened parallel to the surface of the stem and the thickening is uniform, then this is lamellar collenchyma . The cells of angular and lamellar collenchyma are located tightly to each other, without forming intercellular spaces. Loose collenchyma has intercellular spaces, and thickened cell walls are directed towards the intercellular spaces.

Evolutionarily, collenchyma arose from parenchyma. Collenchyma is formed from the main meristem and is located under the epidermis at a distance of one or several layers from it. In young shoot stems it is located in the form of a cylinder along the periphery, in the veins of large leaves - on both sides. Living collenchyma cells are able to grow in length without interfering with the growth of young growing parts of the plant.

Sclerenchyma is the most common mechanical tissue, consisting of cells with lignified (with the exception of flax bast fibers) and uniformly thickened cell walls with a few slit-like pores. Sclerenchyma cells are elongated and have a prosenchymal shape with pointed ends. The shells of sclerenchyma cells are close to steel in strength. The lignin content in these cells increases the strength of sclerenchyma. Sclerenchyma is found in almost all vegetative organs of higher land plants. In aquatic species it is either absent entirely or is poorly represented in the submerged organs of aquatic plants.

There are primary and secondary sclerenchyma. Primary sclerenchyma comes from the cells of the main meristem - procambium or pericycle, secondary - from cambium cells. There are two types of sclerenchyma: sclerenchyma fibers, consisting of dead thick-walled cells with pointed ends, with a lignified shell and a few pores, like bast and wood fibers , or libroform fibers, and sclereids - structural elements of mechanical tissue, located alone or in groups between living cells of different parts of the plant: seed coats, fruits, leaves, stems. The main function of sclereids is to resist compression. The shape and size of sclereids are varied.

6. Conductive fabrics. Conductive tissues transport nutrients in two directions. The ascending (transpiration) flow of liquids (aqueous solutions and salts) goes through the vessels and tracheids of the xylem from the roots up the stem to the leaves and other organs of the plant. The downward flow (assimilation) of organic substances is carried out from the leaves along the stem to the underground organs of the plant through special sieve-like phloem tubes. The conducting tissue of the plant is somewhat reminiscent of the human circulatory system, since it has an axial and radial highly branched network; nutrients enter every cell of a living plant. In each plant organ, xylem and phloem are located side by side and are presented in the form of strands - conducting bundles.

There are primary and secondary conducting tissues. Primary ones differentiate from procambium and are formed in young plant organs; secondary conducting tissues are more powerful and are formed from cambium.

Xylem (wood) is represented by tracheids and trachea , or vessels .

Tracheids are elongated closed cells with obliquely cut jagged ends; in the mature state they are represented by dead prosenchymal cells. The length of the cells is on average 1-4 mm. Communication with neighboring tracheids occurs through simple or bordered pores. The walls are unevenly thickened; according to the nature of the thickening of the walls, tracheids are distinguished as annular, spiral, scalariform, reticulated and porous. Porous tracheids always have bordered pores. Sporophytes of all higher plants have tracheids, and in most horsetails, lycophytes, pteridophytes and gymnosperms they serve as the only conducting elements of the xylem. Tracheids perform two main functions: conducting water and mechanically strengthening the organ.

Trachea or vessels - the most important water-conducting elements of the xylem of angiosperms. Tracheas are hollow tubes consisting of individual segments; in the partitions between the segments there are holes - perforations, thanks to which the fluid flows. Tracheas, like tracheids, are a closed system: the ends of each trachea have beveled transverse walls with bordered pores. The tracheal segments are larger than the tracheids: in diameter they are about different types plants from 0.1-0.15 to 0.3 - 0.7 mm. The length of the trachea ranges from several meters to several tens of meters (for lianas). The trachea consists of dead cells, although in the initial stages of formation they are alive. It is believed that tracheae arose from tracheids in the process of evolution.

In addition to the primary shell, most vessels and tracheids have secondary thickenings in the form of rings, spirals, ladders, etc. Secondary thickenings form on the inner wall of blood vessels. Thus, in an annular vessel, the internal thickenings of the walls are in the form of rings located at a distance from each other. The rings are located across the vessel and slightly oblique. In a spiral vessel, the secondary membrane is layered from the inside of the cell in the form of a spiral; in a mesh vessel, the non-thickened areas of the shell look like slits, reminiscent of mesh cells; in the scalene vessel, thickened places alternate with non-thickened ones, forming a semblance of a ladder.

Tracheids and vessels - tracheal elements - are distributed in the xylem in different ways: in a cross section in continuous rings, forming ring-vascular wood , or dispersed more or less evenly throughout the xylem, forming scattered-vascular wood . The secondary shell is usually impregnated with lignin, giving the plant additional strength, but at the same time limiting its growth in length.

In addition to vessels and tracheids, xylem includes ray elements , consisting of cells forming the medullary rays. The medullary rays consist of thin-walled living parenchyma cells through which nutrients flow horizontally. The xylem also contains living wood parenchyma cells, which function as short-range transport and serve as a storage site for reserve substances. All xylem elements come from the cambium.

Phloem is a conductive tissue through which glucose and other organic substances are transported - products of photosynthesis from leaves to places of their use and deposition (to growth cones, tubers, bulbs, rhizomes, roots, fruits, seeds, etc.). Phloem is also primary and secondary. Primary phloem is formed from procambium, secondary (phloem) - from cambium. Primary phloem lacks medullary rays and a less powerful system of sieve elements than tracheids.

During the formation of a sieve tube, mucus bodies appear in the protoplast of cells - segments of the sieve tube, which take part in the formation of a mucus cord near the sieve plates. This completes the formation of the sieve tube segment. Sieve tubes function in most herbaceous plants one growing season and up to 3-4 years for trees and shrubs. Sieve tubes consist of a number of elongated cells communicating with each other through perforated partitions - strainers . The shells of functioning sieve tubes do not become lignified and remain alive. Old cells are clogged with the so-called corpus callosum, and then they die and are flattened under the pressure of younger functioning cells on them.

Phloem includes phloem parenchyma , consisting of thin-walled cells in which reserve nutrients are deposited. The medullary rays of the secondary phloem also carry out short-range transportation of organic nutrients - products of photosynthesis.

Vascular bundles are strands formed, as a rule, by xylem and phloem. If strands of mechanical tissue (usually sclerenchyma) are adjacent to the conductive bundles, then such bundles are called vascular-fibrous . Other tissues can be included in the vascular bundles - living parenchyma, laticifers, etc. The vascular bundles can be complete, when both xylem and phloem are present, and incomplete, consisting only of xylem (xylem, or woody, vascular bundle) or phloem (phloem, or bast, conducting bundle).

The vascular bundles were originally formed from procambium. There are several types of conductive bundles. Part of the procambium can be preserved and then turn into cambium, then the bundle is capable of secondary thickening. These are open bunches. Such vascular bundles predominate in most dicotyledonous and gymnosperm plants. Plants with open tufts are able to grow in thickness due to the activity of the cambium, with woody areas being approximately three times larger than phloem areas . If, during the differentiation of the vascular bundle from the procambial cord, all the educational tissue is completely spent on the formation of permanent tissues, then the bundle is called closed.

Closed vascular bundles are found in the stems of monocots. Wood and bast in bundles can have different relative positions. In this regard, several types of vascular bundles are distinguished: collateral, bicollateral, concentric and radial. Collateral, or lateral, are bundles in which xylem and phloem are adjacent to each other. Bicollateral, or two-sided, are bundles in which two strands of phloem adjoin the xylem side by side. In concentric bundles, xylem tissue completely surrounds phloem tissue or vice versa. In the first case, such a bundle is called centrifloem. Centrophloem bundles are present in the stems and rhizomes of some dicotyledonous and monocotyledonous plants (begonia, sorrel, iris, many sedges and lilies).

Ferns have them. There are also intermediate vascular bundles between closed collateral and centrifloem ones. In the roots there are radial bundles, in which the central part and rays along the radii are left by wood, and each ray of wood consists of central larger vessels, gradually decreasing along the radii. The number of rays varies from plant to plant. Between the wood rays there are bast areas. The vascular bundles stretch along the entire plant in the form of cords, which begin in the roots and run along the entire plant along the stem to the leaves and other organs. In leaves they are called veins. Main function them - carrying out descending and ascending currents of water and nutrients.

7. Excretory tissues. Excretory, or secretory, tissues are special structural formations capable of releasing metabolic products and droplet-liquid media from a plant or isolating metabolic products in its tissues. Metabolic products are called secretions. If they are released outward, then these are exocrine tissues , if they remain inside the plant, then - internal secretion . As a rule, these are living parenchymal thin-walled cells, but as secretion accumulates in them, they lose their protoplast and their cells become suberized.

The formation of liquid secretions is associated with the activity of intracellular membranes and the Golgi complex, and their origin is with assimilation, storage and integumentary tissues. The main function of liquid secretions is to protect the plant from being eaten by animals, damaged by insects or pathogens. Endocrine tissues are presented in the form of idioblast cells, resin ducts, lacticifers, essential oil canals, secretion receptacles, glandular capitate hairs, glands. Idioblast cells often contain crystals of calcium oxalate (representatives of the Liliaceae, Nettles, etc. families), mucus (representatives families Malvaceae, etc.), terpenoids (representatives of the families Magnoliaceae, Pepper, etc.), etc.

Vegetative organs of higher plants

1. Root and its functions. Root metamorphosis.

2. Escape and escape system.

3. Stem.

The vegetative organs of plants include the root, stem and leaf, which make up the body of higher plants. The body of lower plants (algae, lichens) - thallus, or thallus, is not divided into vegetative organs. The body of higher plants has a complex morphological or anatomical structure. It consistently becomes more complex from bryophytes to flowering plants due to the increasing dismemberment of the body through the formation of a system of branched axes, which leads to an increase in the total area of ​​​​contact with the environment. In lower plants it is a system of thalli, or thallus. , in higher plants - systems of shoots and roots.

Type of branches different groups plants are different. Dichotomous, or forked, branching is distinguished, when the old growth cone is divided into two new ones . This type of branching is found in many algae, some liver mosses, mosses, and angiosperms - in some palm trees. There are isotomic and anisotomic axis systems. In an isotomic system, after the top of the main axis stops growing, two identical lateral branches grow underneath it, and in an anisotomic system, one branch sharply outgrows the other . The most common type of branching is the lateral one, in which lateral axes appear on the main axis. This type of branching is inherent in a number of algae, roots and shoots of higher plants. . For higher plants, two types of lateral branching are distinguished: monopodial and sympodial.

With monopodial branching, the main axis does not stop growing in length and forms lateral shoots below the growth cone, which are weaker than the main axis. Sometimes a false dichotomy occurs in monopodially branching plants , when the growth of the top of the main axis stops, and under it two more or less identical lateral branches, called dichasias (mistletoe, lilac, horse chestnut, etc.), are formed, outgrowing it. Monopodial branching is characteristic of many gymnosperms and herbaceous angiosperms. Sympodial branching is very common, in which the apical bud of the shoot dies over time and one or more lateral buds begin to develop intensively, becoming “leaders” . They form side shoots that protect the shoot that has stopped growing.

The complication of branching, starting from algae thalli, probably occurred in connection with the emergence of plants on land and the struggle for survival in a new air environment. At first, these “amphibious” plants were attached to the substrate with the help of thin root-like threads - rhizoids, which subsequently, due to the improvement of the above-ground part of the plant and the need to extract large volumes of water and nutrients from the soil, evolved into a more advanced organ - the root . There is still no consensus on the order of origin of leaves or stems.

Sympodial branching is more evolutionarily advanced and has a large biological significance. Thus, in case of damage to the apical bud, the role of “leader” is assumed by the lateral shoot. Trees and shrubs with sympodial branching tolerate pruning and crown formation (lilac, boxwood, sea buckthorn, etc.).

Root and root system. Root morphology. The root is the main organ of a higher plant.

The main functions of the root are to anchor the plant in the soil, actively absorb water and minerals from it, synthesize important organic substances, such as hormones and other physiological active substances, storage of substances.

The anatomical structure of the root corresponds to the function of anchoring the plant in the soil. In woody plants, the root has, on the one hand, maximum strength, and on the other, great flexibility. The securing function is facilitated by the appropriate location histological structures(for example, wood is concentrated in the center of the root).

The root is an axial organ, usually cylindrical in shape. It grows as long as the apical meristem, covered with a root cap, is preserved. Leaves never form at the end of the root. The root branches to form a root system.

The collection of roots of one plant forms the root system. The root systems include the main root, lateral and adventitious roots. The main root originates from the embryonic root. Lateral roots extend from it, which can branch. Roots originating from the above-ground parts of the plant - leaves and stems - are called adventitious. Propagation by cuttings is based on the ability of individual parts of a stem, shoot, and sometimes leaf to form adventitious roots.

There are two types of root systems - taproot and fibrous. The tap root system has a clearly visible main root. This system is characteristic of most dicotyledonous plants. The fibrous root system consists of adventitious roots and is observed in most monocots.

Microscopic structure of the root. In a longitudinal section of a young growing root, several zones can be distinguished: the division zone, the growth zone, the absorption zone and the conduction zone. The apex of the root, where the growth cone is located, is covered by a root cap. The cover protects it from damage by soil particles. As the root passes through the soil, the cells of the root cap are constantly sloughed off and die, and new ones are continuously formed to replace them due to the division of cells of the educational tissue of the root tip. This is the division zone. The cells of this zone grow intensively and stretch along the axis of the root, forming a growth zone. At a distance of 1-3 mm from the root tip there are many root hairs (absorption zone), which have a large absorption surface and absorb water and minerals from the soil. Root hairs are short-lived. Each of them represents an outgrowth of a superficial root cell. Between the suction site and the base of the stem there is a conduction zone.

The center of the root is occupied by conductive tissue, and between it and the root skin there is developed tissue consisting of large living cells - parenchyma. Solutions of organic substances necessary for root growth move down through the sieve tubes, and water with mineral salts dissolved in it moves from bottom to top through the vessels.

Water and minerals are absorbed by plant roots largely independently, and there is no direct connection between the two processes. Water is absorbed due to the force, which is the difference between osmotic and turgor pressure, i.e. passively. Minerals are absorbed by plants as a result of active absorption.

Plants are capable of not only absorbing mineral compounds from solutions, but also actively dissolving those insoluble in water chemical compounds. In addition to CO 2, plants emit a number of organic acids - citric, malic, tartaric, etc., which contribute to the dissolution of sparingly soluble soil compounds.

Root modifications . The ability of roots to modify over a wide range is an important factor in the struggle for existence. Due to the acquisition of additional functions, the roots are modified. They can accumulate reserve nutrients - starch, various sugars and other substances. The thickened main roots of carrots, beets, and turnips are called root vegetables. Sometimes adventitious roots, like dahlias, thicken, they are called root tubers. The structure of roots is greatly influenced by environmental factors. A number of tropical woody plants that live in oxygen-poor soils form respiratory roots.

They develop from underground lateral horses and grow vertically upward, rising above water or soil. Their function is to supply the underground parts with air, which is facilitated by a thin bark, numerous lenticels and a highly developed system of air-bearing cavities - intercellular spaces. Aerial roots can also absorb moisture from the air. Adventitious roots growing from the above-ground part of the stem can act as supports. Support horses are often found in tropical trees growing along the shores of the seas in the tidal zone. They provide plant stability in unstable soil. In tropical rain forest trees, the lateral roots often take on a board-like shape. Board-shaped roots usually develop in the absence of a taproot and spread in the surface layers of the soil.

Roots have a complex relationship with organisms living in the soil. Soil bacteria settle in the tissues of the roots of some plants (lateral, birch and some others). The bacteria feed on the organic substances of the root (mainly carbon) and cause the growth of parenchyma at the sites of their penetration - the so-called nodules. Nodule bacteria - nitrifiers have the ability to convert atmospheric nitrogen into compounds that can be absorbed by the plant. Lateral crops such as clover and alfalfa accumulate from 150 to 300 kg of nitrogen per hectare. In addition, legumes use organic substances from the body of bacteria to form seeds and fruits.

The vast majority of flowering plants have symbiotic relationships with fungi.

Venue area. After the root hairs die, the cells of the outer layer of the cortex appear on the surface of the root. By this time, the membranes of these cells become poorly permeable to water and air. Their living contents die. Thus, instead of living root hairs, there are now dead cells on the surface of the root. They protect the internal parts of the root from mechanical damage and pathogenic bacteria. Consequently, that part of the root on which the root hairs have already died will not be able to absorb the roots.

There are 3 kingdoms - plants, animals and fungi.

1. Differences in nutrition

Plants are autotrophs, i.e. They make organic substances for themselves from inorganic substances (carbon dioxide and water) through the process of photosynthesis.

Animals and fungi are heterotrophs, i.e. finished organic substances are obtained from food.

2. Growth or movement

Animals are able to move and grow only before reproduction begins.

Plants and mushrooms do not move, but they grow unlimitedly throughout their lives.

3. Differences in the structure and functioning of the cell

1) Only plants have plastids (chloroplasts, leucoplasts, chromoplasts).

2) Only animals have a cell center (centrioles).*

3) Only animals do not have a large central vacuole. The shell of this vacuole is called tonoplast, and the contents are cell sap. In plants it occupies most of the adult cell. * *

4) Only animals do not have a cell wall (dense shell), in plants it is made of cellulose (fiber), and in fungi it is made of chitin.

5) The storage carbohydrate in plants is starch, and in animals and fungi it is glycogen.

===Correct in the Unified State Examination
666) *Only plants do not have centrioles.
667) **Only plants have vacuoles with cell sap.
668) Only animals have lysosomes.

Analyze the text “Difference between a plant cell and an animal cell.” Fill in the blank text cells using the terms in the list. For each cell indicated by a letter, select the corresponding term from the list provided. A plant cell, unlike an animal cell, has ___(A), which in old cells ___(B) and displaces the cell nucleus from the center to its shell. Cell sap may contain ___ (B), which give it a blue, purple, crimson color, etc. The shell of a plant cell mainly consists of ___ (D).
1) chloroplast
2) vacuole
3) pigment
4) mitochondria
5) merge
6) disintegrate
7) cellulose
8) glucose

Answer

Choose three options. Signs characteristic of mushrooms
1) the presence of chitin in the cell wall
2) storage of glycogen in cells
3) absorption of food by phagocytosis
4) ability for chemosynthesis
5) heterotrophic nutrition
6) limited growth

Answer

Choose three options. Plants, like mushrooms,

2) have limited growth
3) absorb nutrients from the body surface
4) feed on ready-made organic substances
5) contain chitin in cell membranes
6) have a cellular structure

Answer

Choose three options. Mushrooms, like animals,
1) grow throughout life
2) do not contain ribosomes in cells
3) have a cellular structure
4) do not contain mitochondria in cells
5) contain chitin in organisms
6) are heterotrophic organisms

Answer

1. Establish a correspondence between the characteristics and the kingdom of organisms: 1) plants, 2) animals
A) Synthesize organic substances from inorganic ones
B) They have unlimited growth
B) Absorb substances in the form of solid particles
D) The storage nutrient is glycogen.
D) The reserve nutrient is starch.
E) Most organisms do not have cell center centrioles in their cells.

Answer

2. Establish a correspondence between the characteristics of organisms and the kingdoms for which they are characteristic: 1) plants, 2) animals. Write numbers 1 and 2 in the correct order.
A) heterotrophic type of nutrition
B) the presence of chitin in the exoskeleton
B) the presence of educational tissue
D) regulation of life activity only with the help of chemicals
D) formation of urea during metabolism
E) the presence of a rigid cell wall made of polysaccharides

Answer

3. Establish a correspondence between the characteristic of an organism and the kingdom for which this characteristic is characteristic: 1) Plants, 2) Animals. Write numbers 1 and 2 in the order corresponding to the letters.
A) cell wall
B) autotrophs
B) larval stage
D) consumers
D) connective tissue
E) tropisms

Answer

4. Establish a correspondence between organelles and cells: 1) plant, 2) animal. Write numbers 1 and 2 in the order corresponding to the letters.
A) cell wall
B) glycocalyx
B) centrioles
D) plastids
D) starch granules
E) glycogen granules

Answer

5. Establish a correspondence between the characteristics of the vital functions of organisms and the kingdoms for which they are characteristic: 1) Plants, 2) Animals. Write numbers 1 and 2 in the order corresponding to the letters.
A) heterotrophic nutrition in most representatives
B) maturation of gametes by meiosis
B) primary synthesis of organic substances from inorganic substances
D) transport of substances through conductive tissue
D) neurohumoral regulation of vital processes
E) reproduction by spores and vegetative organs

Answer

Choose three correct answers out of six and write down the numbers under which they are indicated. Fungi, unlike plants,
1) belong to nuclear organisms (eukaryotes)
2) grow throughout life
3) feed on ready-made organic substances
4) contain chitin in cell membranes
5) play the role of decomposers in the ecosystem
6) synthesize organic substances from inorganic ones

Answer

Choose three options. The similarity between fungal and animal cells is that they have
1) a shell of chitin-like substance
2) glycogen as a storage carbohydrate
3) decorated core
4) vacuoles with cell sap
5) mitochondria
6) plastids

Answer

Choose three correct answers out of six and write down the numbers under which they are indicated. By what characteristics can mushrooms be distinguished from animals?

2) have a cellular structure
3) grow throughout life
4) have a body consisting of filaments-hyphae
5) absorb nutrients from the surface of the body
6) have limited growth

Answer

Choose three correct answers out of six and write down the numbers under which they are indicated. Mushrooms, like animals,
1) feed on ready-made organic substances
2) have a vegetative body consisting of mycelium
3) lead active image life
4) have unlimited growth
5) store carbohydrates in the form of glycogen
6) form urea during metabolism

Answer

1. Establish a correspondence between the characteristics of organisms and the kingdom to which it belongs: 1) Fungi, 2) Plants. Write numbers 1 and 2 in the correct order.
A) the cell wall contains chitin
B) autotrophic nutrition type
C) form organic substances from inorganic ones
D) starch is a reserve nutrient
D) in natural systems they are decomposers
E) the body consists of mycelium

Answer

2. Establish a correspondence between the structural feature of the cell and the kingdom for which it is characteristic: 1) Fungi, 2) Plants. Write numbers 1 and 2 in the correct order.
A) the presence of plastids
B) absence of chloroplasts
B) reserve substance – starch
D) the presence of vacuoles with cell sap
D) the cell wall contains fiber
E) the cell wall contains chitin

Answer

3. Establish a correspondence between the characteristics of the cell and its type: 1) fungal, 2) plant. Write numbers 1 and 2 in the correct order.
A) reserve carbohydrate – starch
B) chitin gives strength to the cell wall
B) there are no centrioles
D) there are no plastids
D) autotrophic nutrition
E) there is no large vacuole

Answer

4. Establish a correspondence between the characteristics of cells and their type: 1) plant, 2) fungal. Write numbers 1 and 2 in the order corresponding to the letters.
A) phototrophic nutrition
B) heterotrophic nutrition
B) the presence of a cellulose shell
D) storage substance - glycogen
D) the presence of a large storage vacuole
E) the absence of a cell center in most centrioles

Answer

5. Establish a correspondence between the characteristics of cells and the kingdoms of organisms to which these cells belong: 1) Plants, 2) Fungi. Write numbers 1 and 2 in the order corresponding to the letters.
A) cell wall made of chitin
B) the presence of large vacuoles with cell sap
C) absence of centrioles of the cell center in most representatives
D) storage carbohydrate glycogen
D) heterotrophic mode of nutrition
E) the presence of various plastids

Answer

1. The characteristics listed below, except two, are used to describe the characteristics of the cells shown in the figure. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) have a formed core
2) are heterotrophic
3) capable of photosynthesis
4) contain a central vacuole with cell sap
5) accumulate glycogen

Answer

2. All of the characteristics listed below, except two, are used to describe the cell shown in the figure. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) the shape of the cell is maintained by turgor
2) storage substance - starch
3) the cell does not have centrioles
4) the cell does not have a cell wall
5) all proteins are synthesized in chloroplasts

Answer

3. The terms listed below, except two, are used to characterize the cell shown in the figure. Identify two terms that “drop out” from the general list and write down the numbers under which they are indicated.
1) starch
2) mitosis
3) meiosis
4) phagocytosis
5) chitin

Answer

4. All but two of the terms listed below are used to describe the cell shown in the figure. Identify two terms that “drop out” from the general list and write down the numbers under which they are indicated
1) photosynthesis
2) cell wall
3) chitin
4) nucleoid
5) core

Answer

All of the characteristics listed below, except two, are used to describe the cell shown in the figure. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) cells are always single
2) eat osmotrophically
3) protein is synthesized by ribosomes
4) contain a cellulose wall
5) DNA is in the nucleus

Answer

All of the characteristics listed below, except two, are used to describe the cell shown in the figure. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) has a glycocalyx
2) has a cell wall
3) feeds autotrophically
4) contains a cell center
5) divides by mitosis

Answer

In the form of what cell compound various organisms store glucose? Identify two true statements from the general list and write down the numbers under which they are indicated.
1) Plants store glucose in the form of glycogen
2) Animals store glucose in the form of sucrose
3) Plants store glucose in the form of starch
4) Fungi and plants store glucose in the form of cellulose
5) Fungi and animals store glucose in the form of glycogen

Answer

Choose three correct answers out of six and write down the numbers under which they are indicated. The following characteristics are characteristic of mushrooms:
1) are prenuclear organisms
2) act as decomposers in the ecosystem
3) have root hairs
4) have limited growth
5) by type of nutrition - heterotrophs
6) contain chitin in cell membranes

Answer

Choose three correct answers out of six and write down the numbers under which they are indicated in the answer. From the listed characteristics, select those that fungal cells have.
1) the hereditary apparatus is located in the nucleotide
2) the cell wall contains chitin
3) eukaryotic cell
4) storage substance - glycogen
5) there is no cell membrane
6) type of nutrition – autotrophic

Answer

1. Choose three options. The cells of a flowering plant differ from the cells of an animal body in the presence
1) fiber casings
2) chloroplasts
3) decorated core
4) vacuoles with cell sap
5) mitochondria
6) endoplasmic reticulum

Answer

2. Choose three correct answers out of six and write down the numbers under which they are indicated. The cells of plant organisms, unlike animals, contain
1) chloroplasts
2) mitochondria
3) nucleus and nucleolus
4) vacuoles with cell sap
5) cell wall made of cellulose
6) ribosomes

Answer

Select three elements that distinguish a plant cell from an animal cell.
1) absence of mitochondria
2) the presence of leukocytes
3) absence of glycocalyx
3) presence of thylakoids
5) the presence of cell sap
6) absence of a plasma membrane

Answer

Analyze the text "Mosses". For each cell indicated by a letter, select the corresponding term from the list provided. Mosses are ________ (A) plants, since they reproduce by spores that are formed in special organs - ________ (B). In our forests there are green mosses, for example, cuckoo flax, and white mosses, for example, ________ (B). Water is extremely important for the life of mosses, so they are often found near forest standing bodies of water: lakes and swamps. Centuries-old deposits of moss in swamps form deposits of ________ (D) - valuable fertilizer and fuel.
1) inferior
2) box
3) seed
4) sorus
5) spore
6) sphagnum
7) peat
8) flowering

Answer

Establish a correspondence between the characteristics of the cell and its type: 1) bacterial, 2) fungal, 3) plant. Write the numbers 1, 2 and 3 in the correct order.
A) absence of membrane organelles
B) storage substance – starch
B) the ability to chemosynthesize
D) the presence of a nucleoid
D) the presence of chitin in the cell wall

Answer

Select three characteristics that distinguish mushrooms from plants.
1) chemical composition of the cell wall
2) unlimited growth
3) immobility
4) way of eating
5) reproduction by spores
6) presence of fruiting bodies

Answer

What features, unlike animal and fungal cells, does a plant cell have?
1) forms a cellulose cell wall
2) includes ribosomes
3) has the ability to divide repeatedly
4) accumulates nutrients
5) contains leukoplasts
6) does not have centrioles

Answer

1) chloroplasts
2) central vacuole
3) endoplasmic reticulum
4) mitochondria
5) Golgi apparatus

Answer

All but two of the following organelles are present in all types of eukaryotic cells. Identify two characteristics that “drop out” from the general list, and write down the numbers under which they are indicated in your answer.
1) plasma membrane
2) endoplasmic reticulum
3) flagella
4) mitochondria
5) chloroplasts

Answer

1. All but two of the terms listed below are used to describe a fungal cell. Identify two terms that “drop out” from the general list and write down the numbers under which they are indicated in the table.
1) core
2) chemosynthesis
3) cell wall
4) autotrophic nutrition
5) glycogen

Answer

2. All of the characteristics listed below, except two, are used to describe the structure of a fungal cell. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) presence of a designed core
2) the presence of a cellulose shell
3) ability for phagocytosis
4) the presence of membrane organelles
5) the presence of glycogen as a reserve substance

Answer

All but two of the characteristics listed below are used to describe the structure of most plant cells. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) various plastids
2) cellulose shell
3) centrioles of the cell center
4) glycocalyx
5) vacuoles with cell sap

Answer

All but two of the characteristics listed below are used to describe the structure of most animal cells. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) centrioles of the cell center
2) cell membrane made of chitin
3) semi-autonomous organoids
4) plastids
5) glycocalyx

Answer

1. Find three errors in the given text and indicate the numbers of the sentences in which they were made.(1) Plants, like other organisms, have a cellular structure, eat, breathe, grow, and reproduce. (2) As members of one kingdom, plants have characteristics that distinguish them from other kingdoms. (3) Plant cells have a cell wall consisting of cellulose, plastids, and vacuoles with cell sap. (4) The cells of higher plants have centrioles. (5) In plant cells, ATP synthesis occurs in lysosomes. (6) Glycogen is a reserve nutrient in plant cells. (7) According to the method of nutrition, most plants are autotrophs.

Answer

2. Find three errors in the given text. Indicate the numbers of the proposals in which they are made.(1) Eukaryotic cells have a separate nucleus. (2) Plastids and mitochondria of eukaryotic cells contain ribosomes. (3) The cytoplasm of prokaryotic and eukaryotic cells contains ribosomes, the Golgi complex and the endoplasmic reticulum. (4) The cell wall of plant cells contains cellulose, the cell wall of animal cells contains glycogen. (5) bacterial cell reproduces using spores. (6) A eukaryotic cell divides by mitosis and meiosis. (7) Fungal spores are designed to reproduce.

Answer

Establish a correspondence between the characteristics and kingdoms of organisms: 1) Animals, 2) Fungi. Write numbers 1 and 2 in the order corresponding to the letters.
A) cell walls contain chitin
B) the presence of mycelium consisting of filaments-hyphae
B) the presence of a glycocalyx on cell membranes
D) growth throughout life
D) ability to move independently

Answer

Establish a correspondence between the characteristics of organisms and the kingdoms for which they are characteristic: 1) Fungi, 2) Animals. Write numbers 1 and 2 in the order corresponding to the letters.
A) rigid cell wall
B) active movement in space
C) absorption of nutrients by the body surface by all representatives of the kingdom
D) unlimited growth for all representatives
D) external and internal fertilization
E) the presence of tissues and organs

Answer

Look at the picture depicting this cell and determine (A) the type of this cell, (B) its type of nutrition, (C) the organelle indicated in the picture by number 1. For each letter, select the corresponding term from the list provided.
1) bacterial
2) mitochondria
3) autotrophic
4) vegetable
5) construction
6) heterotrophic
7) animal
8) core

Answer

Match the characteristics and kingdoms of the organisms shown in the figure. Write the numbers 1 and 2 in the sequence corresponding to the letters.
A) characterized by an autotrophic type of nutrition
B) have a variety of tissues and organs
C) most representatives have centrioles of the cell center in their cells
D) reserve nutrient - glycogen
D) many representatives have a fruiting body
E) are producers in ecosystems

Answer

© D.V. Pozdnyakov, 2009-2019

At the dawn of the development of life on Earth, all cellular forms were represented by bacteria. They absorbed organic substances dissolved in the primordial ocean through the surface of the body.

Over time, some bacteria have adapted to produce organic substances from inorganic ones. To do this, they used the energy of sunlight. The first ecological system arose in which these organisms were producers. As a result, oxygen released by these organisms appeared in the Earth's atmosphere. With its help, you can get much more energy from the same food, and use the additional energy to complicate the structure of the body: dividing the body into parts.

One of the important achievements of life is the separation of the nucleus and cytoplasm. The nucleus contains hereditary information. A special membrane around the core made it possible to protect against accidental damage. As needed, the cytoplasm receives commands from the nucleus that direct the life and development of the cell.

Organisms in which the nucleus is separated from the cytoplasm have formed the nuclear superkingdom (these include plants, fungi, and animals).

Thus, the cell - the basis of the organization of plants and animals - arose and developed in the course of biological evolution.

Even with the naked eye, or even better under a magnifying glass, you can see that the flesh of a ripe watermelon consists of very small grains, or grains. These are cells - the smallest “building blocks” that make up the bodies of all living organisms, including plants.

The life of a plant is carried out by the combined activity of its cells, creating a single whole. With multicellularity of plant parts, there is a physiological differentiation of their functions, specialization of various cells depending on their location in the plant body.

A plant cell differs from an animal cell in that it has a dense membrane that covers the internal contents on all sides. The cell is not flat (as it is usually depicted), it most likely looks like a very small bubble filled with mucous contents.

Structure and functions of a plant cell

Let's consider a cell as a structural and functional unit of an organism. The outside of the cell is covered with a dense cell wall, in which there are thinner sections called pores. Beneath it there is a very thin film - a membrane covering the contents of the cell - the cytoplasm. In the cytoplasm there are cavities - vacuoles filled with cell sap. In the center of the cell or near the cell wall there is a dense body - a nucleus with a nucleolus. The nucleus is separated from the cytoplasm by the nuclear envelope. Small bodies called plastids are distributed throughout the cytoplasm.

Structure of a plant cell

Structure and functions of plant cell organelles

Organoid	Drawing	Description	Function	Peculiarities
Cell wall or plasma membrane		Colourless, transparent and very durable	Passes substances into and out of the cell.	Cell membrane is semi-permeable
Cytoplasm		Thick viscous substance	All other parts of the cell are located in it	Is in constant motion
Core ( an important part cells)		Round or oval	Ensures the transfer of hereditary properties to daughter cells during division	Central part of the cell
		Spherical or irregular in shape	Takes part in protein synthesis
		A reservoir separated from the cytoplasm by a membrane. Contains cell sap	Spare nutrients and waste products that the cell does not need accumulate.	As the cell grows, small vacuoles merge into one large (central) vacuole
Plastids		Chloroplasts	They use the light energy of the sun and create organic from inorganic	The shape of discs delimited from the cytoplasm by a double membrane
		Chromoplasts	Formed as a result of the accumulation of carotenoids	Yellow, orange or brown
		Leukoplasts	Colorless plastids
Nuclear envelope		Consists of two membranes (outer and inner) with pores	Separates the nucleus from the cytoplasm	Allows exchange between the nucleus and cytoplasm

The living part of a cell is a membrane-bound, ordered, structured system of biopolymers and internal membrane structures involved in a set of metabolic and energy processes that maintain and reproduce the entire system as a whole.

An important feature is that the cell does not have open membranes with free ends. Cell membranes always limit cavities or areas, closing them on all sides.

Modern generalized diagram of a plant cell

Plasmalemma(outer cell membrane) is an ultramicroscopic film 7.5 nm thick, consisting of proteins, phospholipids and water. This is a very elastic film that is well wetted by water and quickly restores integrity after damage. It has a universal structure, i.e. typical for all biological membranes. In plant cells, outside the cell membrane there is a strong cell wall that creates external support and maintains the shape of the cell. It consists of fiber (cellulose), a water-insoluble polysaccharide.

Plasmodesmata plant cells, are submicroscopic tubules that penetrate the membranes and are lined with a plasma membrane, which thus passes from one cell to another without interruption. With their help, intercellular circulation of solutions containing organic nutrients occurs. They also transmit biopotentials and other information.

Porami called openings in the secondary membrane, where the cells are separated only by the primary membrane and the median lamina. The areas of the primary membrane and the middle plate separating the adjacent pores of adjacent cells are called the pore membrane or the closing film of the pore. The closing film of the pore is pierced by plasmodesmal tubules, but a through hole is usually not formed in the pores. Pores facilitate the transport of water and solutes from cell to cell. Pores form in the walls of neighboring cells, usually one opposite the other.

Cell membrane has a well-defined, relatively thick shell of a polysaccharide nature. The shell of a plant cell is a product of the activity of the cytoplasm. The Golgi apparatus and the endoplasmic reticulum take an active part in its formation.

Structure of the cell membrane

The basis of the cytoplasm is its matrix, or hyaloplasm, a complex colorless, optically transparent colloidal system capable of reversible transitions from sol to gel. The most important role of hyaloplasm is to unite all cellular structures into a single system and ensure interaction between them in the processes of cellular metabolism.

Hyaloplasma(or cytoplasmic matrix) is internal environment cells. It consists of water and various biopolymers (proteins, nucleic acids, polysaccharides, lipids), of which the main part consists of proteins of varying chemical and functional specificity. The hyaloplasm also contains amino acids, monosaccharides, nucleotides and other low molecular weight substances.

Biopolymers form a colloidal medium with water, which, depending on conditions, can be dense (in the form of a gel) or more liquid (in the form of a sol), both throughout the cytoplasm and in its individual sections. In the hyaloplasm, various organelles and inclusions are localized and interact with each other and the hyaloplasm environment. Moreover, their location is most often specific to certain types cells. Through the bilipid membrane, the hyaloplasm interacts with the extracellular environment. Therefore, hyaloplasm is a dynamic medium and plays important role in the functioning of individual organelles and the life of cells as a whole.

Cytoplasmic formations - organelles

Organelles (organelles) - structural components cytoplasm. They have a certain shape and size and are obligatory cytoplasmic structures of the cell. If they are absent or damaged, the cell usually loses its ability to continue to exist. Many of the organelles are capable of division and self-reproduction. Their sizes are so small that they can only be seen with an electron microscope.

Core

The nucleus is the most prominent and usually the largest organelle of the cell. It was first explored in detail by Robert Brown in 1831. The nucleus provides the most important metabolic and genetic functions of the cell. It is quite variable in shape: it can be spherical, oval, lobed, or lens-shaped.

The nucleus plays a significant role in the life of the cell. A cell from which the nucleus has been removed no longer secretes a membrane and stops growing and synthesizing substances. The products of decay and destruction intensify in it, as a result of which it quickly dies. The formation of a new nucleus from the cytoplasm does not occur. New nuclei are formed only by dividing or crushing the old one.

The internal contents of the nucleus are karyolymph (nuclear juice), which fills the space between the structures of the nucleus. It contains one or more nucleoli, as well as a significant number of DNA molecules connected to specific proteins - histones.

Core structure

Nucleolus

The nucleolus, like the cytoplasm, contains predominantly RNA and specific proteins. Its most important function is that it forms ribosomes, which carry out the synthesis of proteins in the cell.

Golgi apparatus

The Golgi apparatus is an organelle that is universally distributed in all types of eukaryotic cells. It is a multi-tiered system of flat membrane sacs, which thicken along the periphery and form vesicular processes. It is most often located near the nucleus.

Golgi apparatus

The Golgi apparatus necessarily includes a system of small vesicles (vesicles), which are detached from thickened cisterns (discs) and are located along the periphery of this structure. These vesicles play the role of an intracellular transport system for specific sector granules and can serve as a source of cellular lysosomes.

The functions of the Golgi apparatus also consist of the accumulation, separation and release outside the cell with the help of vesicles of intracellular synthesis products, decay products, and toxic substances. Products of the synthetic activity of the cell, as well as various substances entering the cell from environment through the channels of the endoplasmic reticulum, are transported to the Golgi apparatus, accumulate in this organelle, and then in the form of droplets or grains enter the cytoplasm and are either used by the cell itself or excreted outside. In plant cells, the Golgi apparatus contains enzymes for the synthesis of polysaccharides and the polysaccharide material itself, which is used to build the cell wall. It is believed that it is involved in the formation of vacuoles. The Golgi apparatus was named after the Italian scientist Camillo Golgi, who first discovered it in 1897.

Lysosomes

Lysosomes are small vesicles bounded by a membrane whose main function is to carry out intracellular digestion. The use of the lysosomal apparatus occurs during the germination of a plant seed (hydrolysis of reserve nutrients).

Structure of a lysosome

Microtubules

Microtubules are membranous, supramolecular structures consisting of protein globules arranged in spiral or straight rows. Microtubules perform a predominantly mechanical (motor) function, ensuring the mobility and contractility of cell organelles. Located in the cytoplasm, they give the cell a certain shape and ensure the stability of the spatial arrangement of organelles. Microtubules promote the movement of organelles to places that are determined physiological needs cells. A significant number of these structures are located in the plasmalemma, near the cell membrane, where they participate in the formation and orientation of cellulose microfibrils of plant cell walls.

Microtubule structure

Vacuole

The vacuole is the most important component of plant cells. It is a kind of cavity (reservoir) in the mass of the cytoplasm, filled with an aqueous solution of mineral salts, amino acids, organic acids, pigments, carbohydrates and separated from the cytoplasm by a vacuolar membrane - the tonoplast.

Cytoplasm fills the entire internal cavity only in the youngest plant cells. As the cell grows, the spatial arrangement of the initially continuous mass of cytoplasm changes significantly: small vacuoles filled with cell sap appear, and the entire mass becomes spongy. With further cell growth, individual vacuoles merge, pushing the layers of cytoplasm to the periphery, as a result of which the formed cell usually contains one large vacuole, and the cytoplasm with all organelles is located near the membrane.

Water-soluble organic and mineral compounds of vacuoles determine the corresponding osmotic properties of living cells. This solution of a certain concentration is a kind of osmotic pump for controlled penetration into the cell and release of water, ions and metabolite molecules from it.

In combination with the cytoplasm layer and its membranes, characterized by semi-permeable properties, the vacuole forms an effective osmotic system. Osmotically determined are such indicators of living plant cells as osmotic potential, suction force and turgor pressure.

Structure of the vacuole

Plastids

Plastids are the largest (after the nucleus) cytoplasmic organelles, inherent only in the cells of plant organisms. They are not found only in mushrooms. Plastids play an important role in metabolism. They are separated from the cytoplasm by a double membrane shell, and some types have a well-developed and ordered system of internal membranes. All plastids are of the same origin.

Chloroplasts- the most common and most functionally important plastids of photoautotrophic organisms that carry out photosynthetic processes, ultimately leading to the formation of organic substances and the release of free oxygen. The chloroplasts of higher plants have a complex internal structure.

Chloroplast structure

The sizes of chloroplasts in different plants are not the same, but on average their diameter is 4-6 microns. Chloroplasts are able to move under the influence of the movement of the cytoplasm. In addition, under the influence of lighting, active movement of amoeboid-type chloroplasts towards the light source is observed.

Chlorophyll is the main substance of chloroplasts. Thanks to chlorophyll, green plants are able to use light energy.

Leukoplasts(colorless plastids) are clearly defined cytoplasmic bodies. Their sizes are somewhat smaller than the sizes of chloroplasts. Their shape is also more uniform, approaching spherical.

Leukoplast structure

Found in epidermal cells, tubers, and rhizomes. When illuminated, they very quickly turn into chloroplasts with a corresponding change in the internal structure. Leucoplasts contain enzymes with the help of which starch is synthesized from excess glucose formed during photosynthesis, the bulk of which is deposited in storage tissues or organs (tubers, rhizomes, seeds) in the form of starch grains. In some plants, fats are deposited in leucoplasts. The reserve function of leukoplasts occasionally manifests itself in the formation of reserve proteins in the form of crystals or amorphous inclusions.

Chromoplasts in most cases they are derivatives of chloroplasts, occasionally - leucoplasts.

Chromoplast structure

The ripening of rose hips, peppers, and tomatoes is accompanied by the transformation of chloro- or leucoplasts of the pulp cells into caratinoid plasts. The latter contain predominantly yellow plastid pigments - carotenoids, which, when ripe, are intensively synthesized in them, forming colored lipid droplets, solid globules or crystals. In this case, chlorophyll is destroyed.

Mitochondria

Mitochondria are organelles characteristic of most plant cells. They have a variable shape of sticks, grains, and threads. Discovered in 1894 by R. Altman using a light microscope, and the internal structure was studied later using an electron microscope.

The structure of mitochondria

Mitochondria have a double-membrane structure. The outer membrane is smooth, the inner one forms various shapes outgrowths are tubes in plant cells. The space inside the mitochondrion is filled with semi-liquid content (matrix), which includes enzymes, proteins, lipids, calcium and magnesium salts, vitamins, as well as RNA, DNA and ribosomes. The enzymatic complex of mitochondria accelerates the complex and interconnected mechanism of biochemical reactions that result in the formation of ATP. In these organelles, cells are provided with energy - the energy of chemical bonds of nutrients is converted into high-energy bonds of ATP in the process of cellular respiration. It is in mitochondria that the enzymatic breakdown of carbohydrates, fatty acids, and amino acids occurs with the release of energy and its subsequent conversion into ATP energy. The accumulated energy is spent on growth processes, on new syntheses, etc. Mitochondria multiply by division and live for about 10 days, after which they are destroyed.

Endoplasmic reticulum

The endoplasmic reticulum is a network of channels, tubes, vesicles, and cisterns located inside the cytoplasm. Discovered in 1945 by the English scientist K. Porter, it is a system of membranes with an ultramicroscopic structure.

Structure of the endoplasmic reticulum

The entire network is united into a single whole with the outer cell membrane of the nuclear envelope. There are smooth and rough ER, which carries ribosomes. On the membranes of the smooth ER there are enzyme systems involved in fat and carbohydrate metabolism. This type of membrane predominates in seed cells rich in storage substances (proteins, carbohydrates, oils); ribosomes are attached to the granular EPS membrane, and during the synthesis of a protein molecule, the polypeptide chain with ribosomes is immersed in the EPS channel. The functions of the endoplasmic reticulum are very diverse: transport of substances both within the cell and between neighboring cells; division of a cell into separate sections in which various physiological processes and chemical reactions simultaneously take place.

Ribosomes

Ribosomes are non-membrane cellular organelles. Each ribosome consists of two particles that are not identical in size and can be divided into two fragments, which continue to retain the ability to synthesize protein after combining into a whole ribosome.

Ribosome structure

Ribosomes are synthesized in the nucleus, then leave it, moving into the cytoplasm, where they attach to outer surface membranes of the endoplasmic reticulum or are located freely. Depending on the type of protein being synthesized, ribosomes can function alone or be combined into complexes - polyribosomes.

Many key differences between plants and animals originate in structural differences at the cellular level. Some have some parts that others have, and vice versa. Before we find the main difference between an animal cell and a plant cell (table later in the article), let's find out what they have in common, and then explore what makes them different.

Animals and plants

Are you slouched in your chair reading this article? Try to sit up straight, extend your arms to the sky and stretch. Feeling good, right? Whether you like it or not, you are an animal. Your cells are soft blobs of cytoplasm, but you can use your muscles and bones to stand and move around. Hetorotrophs, like all animals, must receive nutrition from other sources. If you feel hungry or thirsty, you just need to get up and walk to the refrigerator.

Now think about plants. Imagine a tall oak tree or tiny blades of grass. They stand upright without muscles or bones, but they cannot afford to walk anywhere to get food and drink. Plants, autotrophs, create their own products using the energy of the sun. The difference between an animal cell and a plant cell in Table No. 1 (see below) is obvious, but there are also many similarities.

general characteristics

Plant and animal cells are eukaryotic, and this is already a great similarity. They have a membrane-bound core that contains genetic material (DNA). A semipermeable plasma membrane surrounds both types of cells. Their cytoplasm contains many of the same parts and organelles, including ribosomes, Golgi complexes, endoplasmic reticulum, mitochondria and peroxisomes, among others. While plant and animal cells are eukaryotic and have many similarities, they also differ in several ways.

Features of plant cells

Now let's look at the features How can most of them stand upright? This ability is due to the cell wall, which surrounds the membranes of all plant cells, provides support and rigidity and often gives them a rectangular or even hexagonal shape. appearance when observed through a microscope. All these structural units have a rigid, regular shape and contain many chloroplasts. The walls can be several micrometers thick. Their composition varies among plant groups, but they typically consist of fibers of the carbohydrate cellulose embedded in a matrix of proteins and other carbohydrates.

Cell walls help maintain strength. The pressure created by the absorption of water contributes to their hardness and makes it possible for vertical growth. Plants are unable to move from place to place, so they need to make their own food. An organelle called a chloroplast is responsible for photosynthesis. Plant cells can contain several such organelles, sometimes hundreds.

Chloroplasts are surrounded by a double membrane and contain stacks of membrane-bound disks in which special pigments absorb sunlight, and this energy is used to power the plant. One of the most famous structures is the large central vacuole. occupies most of the volume and is surrounded by a membrane called tonoplast. It stores water, as well as potassium and chloride ions. As the cell grows, the vacuole absorbs water and helps elongate the cells.

Differences between an animal cell and a plant cell (Table No. 1)

Plant and animal structural units have some differences and similarities. For example, the former do not have a cell wall and chloroplasts, they are round and irregular in shape, while plants have a fixed rectangular shape. Both are eukaryotic, so they have a number of common features, such as the presence of a membrane and organelles (nucleus, mitochondria and endoplasmic reticulum). So, let's look at the similarities and differences between plant and animal cells in Table No. 1:

Animals vs plants

What conclusion can be drawn from the table “Difference between an animal cell and a plant cell”? Both are eukaryotic. They have true nuclei where the DNA is located and are separated from other structures by a nuclear membrane. Both types have similar reproductive processes, including mitosis and meiosis. Animals and plants need energy; they must grow and maintain normal energy through the process of respiration.

Both have structures known as organelles that are specialized to perform functions necessary for normal functioning. The presented differences between an animal cell and a plant cell in Table No. 1 are supplemented by some common features. It turns out they have a lot in common. Both have some of the same components, including the nucleus, Golgi complex, endoplasmic reticulum, ribosomes, mitochondria, and so on.

What is the difference between a plant cell and an animal cell?

Table No. 1 presents the similarities and differences quite briefly. Let's consider these and other points in more detail.

• Size. Animal cells are usually smaller than plant cells. The former range from 10 to 30 micrometers in length, while plant cells have a length range of 10 to 100 micrometers.
• Form. Animal cells come in a variety of sizes and are typically round or irregular in shape. Plants are more similar in size and tend to be rectangular or cubic in shape.
• Energy storage. Animal cells store energy in the form of complex carbohydrates (glycogen). Plants store energy in the form of starch.
• Differentiation. In animal cells, only stem cells are capable of transitioning into others. Most types of plant cells are not capable of differentiation.
• Height. Animal cells increase in size due to the number of cells. Plants absorb more water in the central vacuole.
• Centrioles. Animal cells contain cylindrical structures that organize the assembly of microtubules during cell division. Plants, as a rule, do not contain centrioles.
• Cilia. They are found in animal cells but are not common in plant cells.
• Lysosomes. These organelles contain enzymes that digest macromolecules. Plant cells rarely contain the function of a vacuole.
• Plastids. Animal cells do not have plastids. Plant cells contain plastids, such as chloroplasts, which are essential for photosynthesis.
• Vacuole. Animal cells can have many small vacuoles. Plant cells have a large central vacuole, which can occupy up to 90% of the cell volume.

Structurally, plant and animal cells are very similar, containing membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes and peroxisomes. Both also contain similar membranes, cytosol, and cytoskeletal elements. The functions of these organelles are also very similar. However, the small difference between a plant cell and an animal cell (Table No. 1) that exists between them is very significant and reflects the difference in the functions of each cell.

So, we found out what their similarities and differences are. The common features are the structural plan, chemical processes and composition, division and genetic code.

At the same time, these smallest units are fundamentally different in the way they feed.

Instructions

The main difference between a plant cell and an animal cell is the way it feeds. Plant cells - they are capable of synthesizing the organic substances necessary for their life, for this they only need light. Animal cells are heterotrophs; They get the substances they need for life from food.

True, there are exceptions among animals. For example, green flagellates: during the day they are capable of photosynthesis, but in the dark they feed on ready-made organic substances.

A plant cell, unlike an animal cell, has a cell wall and, as a result, cannot change its shape. An animal cell can stretch and change because... No.

Differences are also observed in the method of division: when a plant cell divides, a partition is formed in it; An animal cell divides to form a constriction.

In the cells of some multicellular invertebrates (sponges, coelenterates, ciliated worms, some mollusks), capable of intracellular digestion, and in the body of some unicellular organisms, digestive vacuoles containing digestive enzymes are formed. Digestive vacuoles in higher animals are formed in special cells - phagocytes.