Distinguish plant cells from animal cells. A brief comparison of plant and animal cells. Cytoplasmic formations - organelles

All living organisms, with the exception of viruses, are composed of cells. However, viruses cannot be called fully independent living organisms. They need cells to reproduce, meaning they infect other organisms. Thus, we can say that life can only be fully realized in cells.

Cells of different living organisms have overall plan structures, many processes occur in the same way. However, between the cells of organisms belonging to different kingdoms, there are some key differences. For example, bacterial cells do not have nuclei. Animal and plant cells have nuclei. But they have other differences.

Plant cells, unlike animal cells, have three distinct features. These are the presence of a cell wall, plastids and a central vacuole.

Both plant cells and animal cells are surrounded by a cell membrane. It limits the contents of the cell from external environment, allows some substances to pass through and not others. At the same time, in plants with outside there is more from the membrane cell wall, or cell membrane. It is quite rigid and gives the plant cell its shape. Thanks to cell walls, plants do not need a skeleton. Without them, the plants would probably “spread” across the ground. And even grass can stand upright. In order for substances to penetrate through the cell membrane, it has pores. Also, through these pores, cells contact each other, forming cytoplasmic bridges. The cell wall is made of cellulose.

Only plant cells have plastids. Plastids include chloroplasts, chromoplasts and leucoplasts. Most important have chloroplasts. The process of photosynthesis occurs in them, in which organic substances are synthesized from inorganic substances. Animals cannot synthesize organic substances from inorganic ones. They receive ready-made organic substances with food, if necessary, break them down into simpler ones and synthesize their own organic substances. Although plants can photosynthesize, the vast majority of their organic matter also comes from other organic matter. However, the ancestor of everything organic in them is organic matter, which is obtained in chloroplasts from inorganic substances. This substance is glucose.

Large central vacuole characteristic only of plant cells. Animal cells also have vacuoles. However, as the cell grows, they do not merge into one large vacuole, which pushes the rest of the cell contents towards the membrane. This is exactly what happens in plants. The vacuole contains cell sap, which contains mainly storage substances. A large vacuole creates internal pressure on the cell membrane. Thus, along with the cell membrane, it maintains the shape of the cell.

The reserve nutrient of the carbohydrate type in plant cells is starch, and in animal cells it is glycogen. Starch and glycogen are very similar in structure.

Animal cells also have “their own” organelles that do not have higher plants. These are centrioles. They are involved in the process of cell division.

The remaining organelles in plant and animal cells are similar in structure and function. These are mitochondria, Golgi complex, nucleus, endoplasmic reticulum, ribosomes and some others.

Animal and plant cells. Comparison.

Before starting the comparison, it is necessary to mention once again (although this has already been said more than once) that both plant and animal cells are united (together with fungi) into the superkingdom of eukaryotes, and for cells of this superkingdom the presence of a membrane membrane, a morphologically separate nucleus and cytoplasm is typical (matrix) containing various organelles and inclusions.

So, a comparison of animal and plant cells: General signs: 1. Unity of structural systems - cytoplasm and nucleus. 2. The similarity of metabolic and energy processes. 3. Unity of the principle of hereditary code. 4. Universal membrane structure. 5. Unity chemical composition. 6. Similarities in the process of cell division.

Eukaryotic cell

Rice. 1. Scheme of the structure of a eukaryotic cell: 1 - nucleus; 2 - nucleolus; 3 - pores nuclear envelope; 4 - mitochondria; 5 - endocytic invagination; 6 - lysosome; 7 - agranular endoplasmic reticulum; 8 - granular endoplasmic reticulum with polysomes; 9 - ribosomes; 10 - Golgi complex; 11 - plasma membrane. Arrows indicate the direction of flow during endo- and exocytosis.

Scheme of the structure of the plasma membrane:

Rice. 2. Scheme of the structure of the plasma membrane: 1 - phospholipids; 2 - cholesterol; 3 - integral protein; 4 - oligosaccharide side chain.

Electron diffraction pattern of the cell center (two centrioles at the end of the G1 period of the cell cycle):

Structural differences

1. In plants, cells have a hard cellulose shell located

above the membrane, animals do not have it (since plants have a large outer

cell surface is needed for photosynthesis).

2. Plant cells are characterized by large vacuoles (since the

excretory system).

3. Plant cells contain plastids (since plants are autotrophs

photosynthetics).

4. In plant cells (with the exception of some algae) there is no

animals have a formalized cellular center.

Functional differences

1. Method of nutrition: plant cell - autotrophic, animal cell -

heterotrophic.

2. In plants, the main reserve substance is starch (in animals, glycogen).

3. Plant cells are usually more watered (contain

up to 90% water) than animal cells.

4. Synthesis of substances sharply prevails above their decay, so plants

can accumulate enormous biomass and are capable of unlimited growth.

3. Structure of the nucleus and its functions. The nucleus is a cell organelle of particular importance, a metabolic control center, as well as a place for storing and reproducing hereditary information. The shape of the nuclei is varied and usually corresponds to the shape of the cell. Thus, in parenchymal cells the nuclei are round, in prosenchymal cells they are usually elongated. Much less often, kernels can have a complex structure, consist of several lobes or lobes, or even have branched outgrowths. Most often, the cell contains a single nucleus, but in some plants the cells can be multinucleated. In the composition of the nucleus, it is customary to distinguish: a) the nuclear envelope - karyolemma, b) nuclear juice - karyoplasm, c) one or two round nucleoli, d) chromosomes.

The bulk of the dry matter of the nucleus consists of proteins (70-96%) and nucleic acids, in addition, it also contains all the substances characteristic of the cytoplasm.

The nuclear shell is double and consists of outer and inner membranes, which have a structure similar to the membranes of the cytoplasm. The outer membrane is usually connected to the channels of the edoplasmic reticulum in the cytoplasm. Between the two shell membranes there is a space that is wider than the thickness of the membranes. The core shell has numerous pores, the diameter of which is relatively large and reaches 0.02-0.03 microns. Thanks to the pores, the karyoplasm and cytoplasm directly interact.

Nuclear juice (karyoplasm), which is close in viscosity to the mesoplasm of the cell, has a slightly increased acidity. Nuclear sap contains proteins and ribonucleic acids (RNA), as well as enzymes involved in the formation of nucleic acids.

The nucleolus is an obligatory structure of the nucleus that is not in a state of division. The nucleolus is larger in young cells that are actively producing protein. There is reason to believe that the main function of the nucleolus is associated with the formation of ribosomes, which then enter the cytoplasm.

Unlike the nucleolus, chromosomes are usually visible only in dividing cells. The number and shape of chromosomes are constant for all cells of a given organism and for the species as a whole. Since a plant is formed from a zygote after the fusion of female and male germ cells, their number of chromosomes is summed up and considered diploid, denoted as 2n. At the same time, the number of chromosomes of germ cells is single, haploid - n.

Rice. 1 Diagram of the structure of a plant cell

1 – core; 2 – nuclear envelope (two membranes - internal and external - and perinuclear space); 3 – nuclear pore; 4 – nucleolus (granular and fibrillar components); 5 – chromatin (condensed and diffuse); 6 - nuclear juice; 7 – cell wall; 8 – plasmalemma; 9 - plasmodesmata; 10 – endoplasmic agranular reticulum; 11 - endoplasmic granular reticulum; 12 – mitochondria; 13 - free ribosomes; 14 – lysosome; 15 – chloroplast; 16 – dictyosome of the Golgi apparatus; 17 – hyaloplasm; 18 – tonoplast; 19 – vacuole with cell sap.

The nucleus is, first of all, the custodian of hereditary information, as well as the main regulator of cell division and protein synthesis. Protein synthesis occurs in ribosomes outside the nucleus, but under its direct control.

4. Ergastic substances of plant cells.

All cell substances can be divided into 2 groups: constitutional and ergastic substances.

Constitutional substances are part of cellular structures and participate in metabolism.

Ergastic substances (inclusions, inactive substances) are substances that are temporarily or permanently removed from metabolism and are in an inactive state in the cell.

Ergastic substances (inclusions)

Spare substances final products

exchange (slags)

starch (in the form of starch grains)

oils (in the form of lipid drops) crystals

reserve proteins (usually in the form of aleurone grains) salts

Spare substances

1. The main reserve substance of plants is starch – the most characteristic, most common substance specific to plants. This is a radially branched carbohydrate-polysaccharide with the formula (C 6 H 10 O 5) n.

Starch is deposited in the form of starch grains in the stroma of plastids (usually leucoplasts) around the center of crystallization (formation center, center of layering) in layers. Distinguish simple starch grains(one center of layering) (potatoes, wheat) and complex starch grains(2, 3 or more centers of layering) (rice, oats, buckwheat). Starch grain consists of two components: amylase (the soluble part of the grain, thanks to which iodine colors the starch Blue colour) and amylopectin (the insoluble part), which only swells in water. According to their properties, starch grains are spherocrystals. Layering is visible because different layers of grain contain different amounts of water.

Thus, starch is formed only in plastids, in their stroma and stored in the stroma.

Depending on the location, there are several types of starch.

1) Assimilation (primary) starch– is formed in light in chloroplasts. The formation of a solid substance, starch, from glucose produced during photosynthesis prevents a harmful increase in osmotic pressure inside the chloroplast. At night, when photosynthesis stops, primary starch is hydrolyzed to sucrose and monosaccharides and transported to leucoplasts - amyloplasts, where it is deposited as:

2) Reserve (secondary) starch– grains are larger and can occupy the entire leukoplast.

Part of the secondary starch is called protected starch- this is a NZ plant, it is spent only in the most extreme cases.

Starch grains are quite small. Their shape is strictly constant for each plant species. Therefore, they can be used to determine from which plants flour, bran, etc. are prepared.

Starch is found in all plant organs. It forms easily and dissolves easily(this is his big +).

Starch is very important for humans, since our main food is carbohydrates. There is a lot of starch in cereal grains, legumes and buckwheat seeds. It accumulates in all organs, but the richest in it are seeds, underground tubers, rhizomes, and the parenchyma of the conducting tissues of the root and stem.

2. Oils (Lipid drops)

Fatty oilsEssential oils

A) Fixed oils esters of glycerol and fatty acids. The main function is storage. This is the second form of storage substances after starch.

Advantages over starch: occupying a smaller volume, they provide more energy (available in the form of drops).

Flaws: less soluble than starch and more difficult to break down.

Fatty oils are most often found in the hyaloplasm in the form of lipid droplets, sometimes forming large accumulations. Less commonly, they are deposited in leucoplasts - oleoplasts.

Fatty oils are found in all plant organs, but most often in seeds, fruits and wood parenchyma of woody plants (oak, birch).

Meaning for a person: very high, as it is easier to digest than animal fats.

The most important oilseed crops: sunflower (academician Pustovoit created varieties containing up to 55% oil in the seeds) sunflower oil;

Corn corn oil;

Mustard mustard oil;

Rapeseed rapeseed oil;

Linen linseed oil;

Tung tung oil;

Castor bean castor oil.

B) Essential oils – very volatile and aromatic, found in specialized cells of excretory tissues (glands, glandular hairs, receptacles, etc.).

Functions: 1) protect plants from overheating and hypothermia (during evaporation); 2) there is essential oils, killing bacteria and other microorganisms – phytoncides. Phytoncides are usually released by the leaves of plants (poplar, bird cherry, pine).

Meaning for humans:

1) used in perfumery (rose oil is obtained from the petals of the Kazanlak rose; lavender oil, geranium oil, etc.);

2) in medicine ( menthol oil(mint), sage oil (clary sage), thymol oil (thyme), Eucalyptus oil(eucalyptus), fir oil(fir), etc.).

3. Squirrels.

There are 2 types of proteins in a cell:

1) structural proteins– active, are part of the membranes of hyaloplasm, organelles, participate in metabolic processes and determine the properties of organelles and cells as a whole. If there is an excess, some of the proteins can be removed from metabolism and become reserve proteins.

2)Spare proteins

Amorphous (structureless, crystalline

accumulate in the hyaloplasm (small crystals in dehydrated

sometimes in vacuoles) vacuoles – aleurone grains)

Aleurone grains are most often formed in the storage cells of dry seeds (for example, legumes, cereals).

End products of metabolism (slags).

The end products of metabolism are most often deposited in vacuoles, where they are neutralized and do not poison the protoplast. A lot of them accumulate in old leaves, which the plant periodically sheds, as well as in dead cells of the crust, where they do not interfere with the plant.

Slags are crystals of mineral salts. The most common:

1) calcium oxalate(calcium oxalate) – deposited in vacuoles in the form of crystals various shapes. There may be single crystals - single crystals, crystal intergrowths – Druze, stacks of needle-shaped crystals – raphids, very small numerous crystals – crystal sand.

2) calcium carbonate(CaCO 3) - deposited on the inside of the shell, on the outgrowths of the inner walls (cystoliths) of the shell, gives the cell strength.

3) silica(SiO 2) - deposited in cell membranes (horsetails, bamboo, sedges), provides the strength of the membrane (but at the same time fragility).

Usually, waste products are the end products of metabolism, but sometimes, if there is a lack of salts in the cell, crystals can dissolve and minerals again involved in metabolism.

Used Books:

Andreeva I.I., Rodman L.S. Botany: textbook. allowance. - M.: KolosS, 2005. - 517 p.

Serebryakova T.I., Voronin N.S., Elenevsky A.G. and others. Botany with the basics of phytocenology: anatomy and morphology of plants: textbook. - M.: Akademkniga, 2007. - 543 p.

Yakovlev G.P., Chelombitko V.A., Dorofeev V.I. Botany: textbook. - St. Petersburg: SpetsLit, 2008 – 687 p.

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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. When plant parts are multicellular, there is a physiological differentiation of their functions, specialization 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
Nucleus (important part of the cell)		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 the holes in secondary shell, 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 plant cell membrane 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 of cells. Through the bilipid membrane, the hyaloplasm interacts with the extracellular environment. Consequently, hyaloplasm is a dynamic environment and plays an important role in the functioning of individual organelles and the life of cells in general.

Cytoplasmic formations - organelles

Organelles (organelles) are structural components of the 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 essential metabolic and genetic functions cells. 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 has a universal distribution in all varieties 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 intracellular transport system specific sector granules 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, breakdown 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 facilitate the movement of organelles to places determined by the physiological needs of the cell. 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 to cells 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 capable of using 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 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 outgrowths of various shapes - 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 work of a complex and interconnected mechanism biochemical reactions, as a result of which ATP is formed. These organelles provide cells with energy - energy conversion chemical bonds nutrients into high energy ATP bonds in the process 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 the cell into separate sections in which various physiological processes and chemical reactions.

Ribosomes

Ribosomes are non-membrane cell 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.

Analysis of the effectiveness of financial investments.

Financial investments can be in the form of securities, contributions to the authorized capital, granted loans and borrowings.

A retrospective assessment of the effectiveness of financial investments is made by comparing the amount of income received and the amount of expenses of a specific type of asset.

Average annual profitability changes under the influence of the structure of each type of investment and the level of profitability of each deposit.

SrUD = ∑ Sd.v. i × Ud.D i

Assessment and forecasting of the economic efficiency of financial investments is carried out using relative and absolute indicators. The main factors influencing efficiency are:

2. current intrinsic value.

Current intrinsic value depends on 3 factors:

1) Expected arrival Money;

2) Rate of return;

3) Duration of the period of income generation.

TVnSt = ∑ (Exp.DS / (1 + N d) n)

Table 4.

Analysis of the effectiveness of using long-term
financial investments

D total = ∑ Ud.v. i × D r i

Factor analysis of total profitability is carried out using the absolute difference method:

1) ∆ D total. (sp.v.) = (2 × 46 + (-2) × 42.6) / 100 = + 0.068

2) ∆ D total. (D r.) = (-1.6 × 64 + 17.4 × 36) / 100 = 5.24

Balance of factors: 0.068 + 5.24 = 5.31

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. IN 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.

Nucleic acids - DNA and RNA - are the most important biopolymers of the protoplast, the content of which is 1-2% of its mass. These are substances for storing and transmitting hereditary information. DNA is mainly found in the nucleus, RNA - in the cytoplasm and nucleus. DNA contains the carbohydrate component deoxyribose, and RNA contains ribonucleic acid. Nucleic acids are polymers whose monomers are nucleotides. A nucleotide consists of a nitrogenous base, a ribose or deoxyribose sugar, and a phosphoric acid residue. Nucleotides are of five types depending on the nitrogenous base. The DNA molecule is represented by two polynucleotide helical chains, the RNA molecule - by one.

Lipids are fat-like substances contained in an amount of 2-3%. These are reserve energy substances that are also part of the cell wall. Fat-like compounds cover plant leaves with a thin layer, preventing them from getting wet during heavy rains. The protoplast of a plant cell contains simple ( fixed oils) and complex lipids (lipoids, or fat-like substances).

Carbohydrates. Carbohydrates are part of the protoplast of each cell in the form of simple compounds (water-soluble sugars) and complex carbohydrates (insoluble or slightly soluble) - polysaccharides. Glucose (C 6 H 12 O 6) is a monosaccharide. It is especially abundant in sweet fruits; it plays a role in the formation of polysaccharides and easily dissolves in water. Fructose, or fruit sugar, is a monosaccharide that has the same formula, but tastes much sweeter. Sucrose (C 12 H 22 O 11) – disaccharide, or cane sugar; V large quantities found in sugar cane and sugar beet roots. Starch and cellulose are polysaccharides. Starch is a reserve energy polysaccharide, cellulose is the main component of the cell wall. IN cell sap In the roots of dahlia, chicory, dandelion, elecampane and other asteraceae, another polysaccharide is found - inulin.

Organic substances in cells also contain vitamins - physiologically active organic compounds that control the course of metabolism, hormones that regulate the processes of growth and development of the body, phytoncides - liquid or volatile substances secreted by higher plants.

Inorganic substances in the cell. Cells contain from 2 to 6% inorganic substances. More than 80 were found in the cell composition chemical elements. Based on their content, the elements that make up a cell can be divided into three groups.

Macroelements. They account for about 99% of the total cell mass. The concentrations of oxygen, carbon, nitrogen and hydrogen are especially high. Their share makes up 98% of all macroelements. The remaining 2% include potassium, magnesium, sodium, calcium, iron, sulfur, phosphorus, chlorine.

Microelements. These include mainly ions heavy metals, which are part of enzymes, hormones and other vital substances. Their content in the cell ranges from 0.001 to 0.000001%. Microelements include boron, cobalt, copper, molybdenum, zinc, vanadium, iodine, bromine, etc.

Ultramicroelements. Their share does not exceed 0.000001%. These include uranium, radium, gold, mercury, beryllium, cesium, selenium and other rare metals.

Water is an integral part of any cell; it is the main environment of the body, directly involved in many reactions. Water is a source of oxygen released during photosynthesis and hydrogen, which is used to restore the products of carbon dioxide assimilation. Water is a solvent. There are hydrophilic substances (from the Greek "hydros" - water and "phileo" - love), highly soluble in water, and hydrophobic (Greek "phobos" - fear) - substances that are difficult or not at all soluble in water (fats, fat-like substances, etc.). Water is the main means of transport of substances in the body (ascending and descending currents of solutions through the vessels of plants) and in the cell.

3. Cytoplasm. In the protoplast, the majority is occupied by the cytoplasm with organelles, the smaller part is occupied by the nucleus with the nucleolus. Cytoplasm has plasma membranes: 1) plasmalemma - outer membrane (shell); 2) tonoplast - the inner membrane in contact with the vacuole. Between them is mesoplasm - the bulk of the cytoplasm. The mesoplasm includes: 1) hyaloplasm (matrix) – the structureless part of the mesoplasm; 2) endoplasmic reticulum (reticulum); 3) Golgi apparatus; 4) ribosomes; 5) mitochondria (chondriosomes); 6) spherosomes; 7) lysosomes; 8) plastids.