The function of the plastic in the plant cell. What is plastic in biology? Genome and whitexitizing system of plastic plastic

Plasts are included in the structure of the plant cell. They are clearly visible under the microscope, are contained in plants. The exception is single-cell algae, bacteria and mushrooms.

Orgellah contains a genetic code, they are able to reproduce themselves like the synthesis of DNA, proteins. The role and functions of the plastic in the cell is determined by their structure. They are able to accumulate nutrients, act as a depot. Separate types of plastids are performed by the function of photosynthesis under the influence of light energy.

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Depending on weather conditions, growth phases in plant cells are up to three types of plastids. They are presented in the table.

Name of plastic	Color	In which part of the plant	Functions	What contains
	colorful transparent	underground	nutrient stores	Starch enzymes
	green	stem, foliage, immature fruit	photosynthesis of nutrients	chlorophyll
	shades: orange red	buton petals roots leaves in the period of leaves	attraction fatrollians seed distributors	Carotenoids anthocian xanthophil enzymes

There are no clear divisions among these types of plastic. They are similar in structure, capable of transformation:

• leukoplasts under the influence of light are reborn into chloroplasts;
• chloroplasts become chromoplasts under the influence of weather factors (the length of the day, temperature);
• in the laboratory conditions, chromoplasts are glad again, become chloroplasts;
• chloroplasts are transformed into leucoplasts (leaves are released in water in water).

Structure of plastic

The size of organoids is small, from 3 to 10 microns. Usually they have a round or oval shape, convex from above, below.

The structure and functions of the plastic in different phases are changing.

Most have two membranes:

• external (shell):
• internal (immersed in stroma).

In some highly organized plants in the structure of the plastic to four membrane partitions. Due to the membranes form:

• tylakoids - peculiar compartments of various buildings;
• grains - columnar or chain clusters of thylacoids;
• lamella - thylacoids elongated form.

Strom - viscous content similar to the structure of the plastic.

Chloroplasts

Green organoids on the structure are found different shapes, isolated:

• oval;
• spiral-shaped;
• lobed;
• ellipsoid.

An important component of stroma is chlorophyll needed for photosynthesis.

In complex plaststs, elements of structure: proteins, fats, pigments, DNA, RNA.

Chromoplasts

Two-cone, have a different structure:

• tubular;
• spherical;
• cubic;
• crystalline.

Chromoplasts in the structure contain grain starch. Green pigment is completely destroyed in them, other nutrient components of chloroplast are preserved.

Leukoplasts

In structure and composition, stromas are divided into:

• amyloplasts - starch shops, if necessary, they are transformed into monosahara;
• elaialastics (lipidoplastics) they contain fats;
• proteinoplasts - storage protein.

The form is in the form of an oval or ellipse.

Functions of plastic

Initially, chloroplasts and leucoplasts are formed. The role of these plastids is photosynthesis, the production of substances included in the plant cells. Under the influence of light, a clear division of the type of organoids and their functions occurs.

In the cells of high-organized plant species contain miscellaneous number Organoids. They are 10, sometimes the amount reaches 200 units. In the period of cooling in the leaves, the synthesis of certain pigments begins. Due to this, the structure of the organo is changing.

Concentration, the composition of the dye in the fruits of plants depends on the DNA code. Colored pigments become visible after the destruction of chlorophyll. It is afraid of low temperatures. The plant is preparing for the winter period. The role of chromoplasts is attracting and accumulative. Fats, enzymes, proteins originally contained in leucoplasts accumulate in the process of growth and ripeness.

The value of chloroplasts

These organoids meet the function of photosynthesis, cell development. They are stepwise synthesized glucose from nitrogen and water dioxide. The reaction proceeds with oxygen release. The process occurs due to chlorophyll - according to the component composition, this hydrocarbon. Releaseing an electron under the influence of light, it changes the function, becomes a reducing agent.

Functions of chromoplasts

In the boobs process, the structure of organoids changes. Plastoglobules are formed in chromoplasts - nutrient accumulations. Changes, membranes are destroyed, the cell is compacted. The inner structure affects the function of the formation: the color is becoming more attractive, bright due to the growth of the concentration of pigment due to the destruction of the organoid membrane structure.

The role of leucoplasts

The functions of the underground part of the plant depends on the variety of leukoplast. Depending on the DNA code, the structure of the formation varies. The cell functions change, it depends on the component composition - the number of fats, proteins, sugars, starch forming fetus. In the form mostly round, less often oval. This is due to the structure of the cell eukaryotic species.

Pigments of plastic

The structure of cell organoids includes three groups of pigments:

• hrolofil - Magnesium-porphyrin protein complexes of chromoproteins, giving the leaves, the trunk of green color;
• carotinoid - coloring pigment, similar to retinol (vitamin A), depending on the concentration acquire an orange or reddish color;
• xanthophive in essence - oxidized carotene, is contained together with R-carotin, has the same functions;
• ficobilinproteids on the component structure are similar to bile pigtooth-protein compounds. These include: Blue phycocyanines that make painting fruits; Red-burgundy ficoeroidrins.

Origin of plastic

In one hypothesis, they arose from cyanobacteria. Later, the theory of natural symbogenesis of bacteria occurred, which includes chlorophyll, and plastic-like microorganisms. So explained the appearance of mitochondria from eukaryota.

ATTENTION The scientists were given to the pigment structure of plant cells, later left this version. A hypothesis of archaeplastidae plastic from green algae and cyanobacteria appeared. Later, thanks to the symbiosis, the colored simplest algae originated. They are similar in the structure of cell plates:

• contains chlorophyll;
• detected pigment inclusions;
• membrane structure.

What color can there be plasts?

If we consider the plant entirely, three color gamans are distinguished:

• yellow, orange, red plaststs are located in flowers, fruits, root, less often - leaves, trunk;
• the intensity of the color depends on the concentration of the pigment of the caratinoid;
• green organoids - chloroplasts, they are involved in the process of photosynthesis; able to transform into chromoplasts various colors or colorless leucoplasts.

The color of the plastic is interconnected with their functionality. What color is the organoid of flower, fetus, root, depends on the DNA model. Information is reproduced during the growth period of the plant.

Flower pigmentation attracts the attention of insects involved in a medical board, pollination occurs. The bright color of the fruit serves as a signal of the ripening of seeds, bones for animals. They distribute seed material in extensive territory.

Plasts (Greek.plastides - creative, forming) are membrane organides of photosynthetic eukaryotic organoids - higher Plants, lower algae, some unicellular. The plastids are present in all types of plant cells, each type is a set of these organoids. All plaststs are characterized by a number of common features. They have their own genetic apparatus and are surrounded by a shell consisting of two concentric membranes.

All plaststs develop from precipitide. They are small organides present in the cells of the meristem, the fate of which is determined by the needs of differentiated cells. All types of plastic are a single genetic series.

The leukoplasts (Greek.leucos are white) - colorless plastides, which are contained in the cells of plant organs devoid of color. They are rounded formations whose largest size is 2-4 microns. They are surrounded by a shell consisting of two membranes within which protein stromas is located. The style of leukoplasts contains a small number of bubbles and flat tanks - lamella. The leukoplasts are capable of developing in chloroplasts, the process of their development is associated with an increase in the size, complication of the internal structure and the formation of green pigment - chlorophyll. Such a restructuring of the plastic occurs, for example, when greening potato tubers. The leukoplasts are also able to move into chromoplasts. In some tissues, such as endosperm in the grain of cereals, in rhizomes and tubers, leukoplasts turn into a storage storage starch - amyloplasts. Onhegenetic transitions of one form to another irreversible, chromoplast can not form neither chloroplast or leukoplast. Similarly, chloroplast can not return to the state of the leukoplast.

Chloroplasts (chloros-green) are the main form of the plastic in which photosynthesis flows. Chloroplasts of higher plants are lenzide formations whose width is in a short axis 2-4 microns, in length - 5 μm and more. The number of chloroplasts in cells of different plants varies very strongly, in the cells of higher plants, contains from 10 to 30 chloroplasts. In the gigantic cells of the panelial fabric Machorka, about a thousand were found. The chloroplasts of algae were originally called chromatophoras. In green algae, there may be one chromatophore on the cell, in eurlen and dinoflagelly young cells contain from 50 to 80 chloroplasts, old - 200-300. The chloroplasts of algae can be invited, beltid, spiral, plate, starfish, they necessarily have a dense formation of protein nature - pyreneoids, around which starch concentrates.

The ultrastructure of chloroplasts reveals a large similarity with mitochondria, primarily in the structure of the chloroplast shell - peristromia. It is surrounded by two membranes, which are separated by a narrow intermogram space with a width of about 20-30 nm. The outer membrane has a high permeability, internal - less permeable and carries special transport proteins. It should be emphasized that the outer membrane is impenetrable for ATP. The inner membrane surrounds a large central region - stroma, this is an analogue of the mitochondrial matrix. The stromium of chloroplast contains a variety of enzymes, ribosomes, DNA and RNA. There are significant differences. Chloroplasts are much larger than mitochondria. Their inner membrane does not form a cryston and does not contain electron transfer circuits. All the most important functional elements of chloroplast are located in the third membrane, which forms groups of flattened disk-shaped bags - thylacoids, it is called a thylacoid membrane. This membrane includes pigment-protein complexes, primarily chlorophyll, pigments from the carotenoid group, of which carotene and xanthofill are common. In addition, the components of electron transport circuits are included in the thylacoid membrane. Internal cavities of thylacoids create a third inner compartment of chloroplast - thylacoid space. Tylacoids form stacks - margins containing them from several pieces to 50 or more. The size of the Grand, depending on the number of thylacoids in them, can reach 0.5 μm, in this case they are available for observations of the light microscope. Thylacoids in the graars are tightly connected, in the contact site, their membranes The thickness of the layer is about 2 nm. The Gran, except Tylacoids, includes stromas lamella sections. These are flat, extended, perforated bags located in parallel planes of chloroplast. They do not intersect and closed. Stroma lamella bind individual grains. In this case, the cavities of Tylacoids and the cavity of the lamelle are not connected.

The function of chloroplasts is photosynthesis, the formation of organic substances from carbon dioxide and water due to the energy of sunlight. This is one of the most important biological processes, constantly and on a huge scale committed on our planet. Every year, the vegetation of the globe forms more than 100 billion tons. Organic substance, absorbing about 200 billion tons of carbon dioxide and highlighting about 145 billion tons of free oxygen into the external environment.

Chromoplasts are plasts of plant cells having the color of the yellow-orange gamma. They can be defined as sedenive, degrading cellides of the cell, they are formed during the destruction of chloroplasts. This is evidenced by chemical composition plastic. If proteins in chloroplasts make up about 50% of their total mass, and lipids are 30%, then in chromoplasts, this ratio changes as follows: 22% proteins, 58% of lipids, DNA is no longer detected. Coloring chromoplasts depends on the presence of carotenoids and destruction of chlorophyll. Nitrogen-containing compounds (pyrrole derivatives) arising from the decay of chlorophyll leak out of the leaves in the same way as the proteins formed during the decay of the protein-lipid membrane system. Lipids remain inside peristromia. Carotenoids dissolve in them, staining the plates in yellow and orange tones. The formation of chromoplasts from chloroplasts occur in two ways. For example, the licker chromoplasts are formed from pale green chloroplasts containing starch. Gradually disappear chlorophyll and starch, the content of yellow pigment increases, which dissolves in lipid drops, forming globules. Simultaneously with education, the globes occurs the final destruction of the lamellar structure of chloroplast. In the formated chromoplast, only peristromium is preserved, globules cover all its inner surface, and the center of the plast capital looks optically empty. The role of chromoplasts in the cell is not clear. But for the vegetable organism, in general, these plast holders play an important role, since the organs of the plant in which photosynthesis stops, become attractive for insects, birds, other animals that implement plants and spread their fruits and seeds. In the autumn yellowing of the leaves, the destruction of chloroplasts and the formation of chromoplasts leads to the disposal of proteins and nitrogen-containing compounds, which in front of the leaf fall to other organs of the plant.

What is the difference between plant cells from animals? The answer lies in the color of the plants: their color depends on the pigment content in cells. These pigments accumulate in special organelles, which are called plaststs.

in biology?

The distinction of animals is the presence of chloroplasts, leukoplasts and chromoplasts. These organelles are responsible for a number of functions, among which it clearly dominates the photosynthesis process. It is the pigment contained in plastids of plants, responsible for their color.

In the cell of any eukaryotic organism, non-emblems, single-paced and double-graffraged organelles are isolated. Plasts and mitochondria belong to the latest type of cellular structures, since they are surrounded by two layers of CPM.

What is cell plastids? Types of plastic

1. Chloroplasts. The main two-bedroom organhelles of plant cells that are responsible for them consist of tilacoids, on which photosynthetic complexes are located. The function of thylacoids is an increase in the active surface of the organella. What are green plastdoms? which contain green-chlorophyll pigments. Several groups of these molecules are isolated, each of which is responsible for its specific functions. Higher plants are most common chlorophyll butwhich is the main solar energy acceptor at photosynthesis.
2. Leukoplasts. Colorless plasts that perform a sparkling function to they may have an incorrect shape, ranging from the spherical and ending with the belt-shaped one. The leukoplasts often accumulate around the core of the cell, and in the microscope they can only be detected in the case of a large number of granules. Depending on the nature of the substance, three types of leucoplasts differ. Amoplasts serve as a carbohydrate carbohydrate, which plant wants to keep until a certain point. Proteoplasts spare various proteins. Oleoplasts accumulate oils and fats that are a source of lipids. That's what the plastic that performs the Painting function.
3. Chromoplasts. The last type of plastic, which has a characteristic yellow, orange or even red. Chromoplasts are the final stage of the development of chloroplasts when chlorophyl is destroyed, and only fat-soluble carotenoids remain in plastids. Chromoplasts are contained in flower petals, mature fruits, and even in plant barrels. Exact value These organelles are definitely unknown, but it is assumed that they are extinguished for carotenoids, and also give plants a specific color. This coloring attracts insect pollinators, which contributes to the reproduction of plants.

The leukoplasts and chromoplasts are not capable of photosynthesis. Chlorophyll in these organelles was reduced or disappeared, so their function was coordinated.

The role of chloroplasts in the transfer of genetic information

What is not only the energy station of the cell, but also the storage of a part of the cell's hereditary information. It is represented in the form of a ring molecule DNA, which resembles the structure of the nucleoid prokaryot. This circumstance makes it possible to assume the symbiotic origin of the plastic when bacterial cells are absorbed by plant cells, losing their autonomy, but leaving some genes.

DNA chloroplasts refers to cytoplasmic cell heredity. It is transmitted only with the help of genital cells determining the female floor. Sperm can not transfer the male DNA of the plastic.

That as chloroplasts are semi-autonomous organelles, many proteins are synthesized in them. Also in division, these plast holders are replicated independently. However, most of the chloroplast proteins are synthesized using the information from the DNA kernel. That's what plastid plasts from the point of view of genetics and molecular biology.

Chloroplast - Energy Station Cells

In the process of photosynthesis on chloroplast tylacoids, many biochemical reactions proceed. Their main task is the synthesis of glucose, as well as ATP molecules. The latter carry in their chemical bonds a large number of Energy that is vital to the cell.

What is the plastic? This is a source of energy along with mitochondria. Photosynthesis process is divided into light and dark stages. In the process of the light stage of photosynthesis, phosphoric residues to the ADF molecules occurs, and at the outlet of the cell receives ATP.

The plasts are organodes of the protoplast characteristic only for plant cells. They are not only with bacteria, blue-green algae and possibly mushrooms.

At higher plants, plasts are in adult vegetative cells of all organs - in the stem, sheet, root and flower. Plasts are relatively large organides, significantly larger than mitochondria, and sometimes even larger kernel, more dense than the surrounding cytoplasm, well visible in the light microscope. They have a characteristic structure and perform various functionsrelated mainly to the synthesis of organic substances.

In an adult plant cell, depending on the color, forms and functions, three main types of plastic are distinguished: chloroplast (plastta of green), chromoplasts (plasts of yellow and orange) and leucoplasts (colorless plasts). The latter in its size is less than the plastic of the two previous types.

Chloroplasts

The structural basis of chloroplast is proteins (about 50% of dry weight), they also contain 5-10% chlorophyll and 1-2% of carotenoids. As in mitochondria, a small amount of RNA (0.5-3.5%) was found in chloroplasts and even less DNA. The exceptional value of chloroplasts is that the process of photosynthesis occurs in them. Starch, formed under photosynthesis, is called primary, or assimilated, it is postponed in chloroplasts in the form of small starchy grains. For the normal flow of photosynthesis, the presence of chlorophyll is necessary. Chlorophyll is the main ongoing start in the implementation of photosynthesis. It absorbs the energy of light and sends it to the commissioning of photosynthetic reactions. From the plate chlorophyll can be removed by alcohol, acetone or other organic solvents. The role of yellow pigments in photosynthesis is still insufficient enough. It is assumed that they also absorb solar energy and transmit it chlorophyll or with it, they carry out specific reaction, important for photosynthesis.

In accordance with their functions, chloroplasts are mainly in photosynthetic organs and tissues facing the light - in the leaves and young stems, immature fruits. Sometimes chloroplasts are even in roots, for example, in the apparent roots of corn. But their main number is concentrated in the cells of the mesophyll (pulp) sheet.

Unlike other organoids, the chloroplasts of higher plants are characterized by monotony and constancy of form and sizes. Most often, they have a disco-shaped or lenzide form and when they are plastics, they have rounded or polygonal outlines. In this case, they are often called also chlorophyll grains. The size of chloroplasts is quite constant and even different species Higher plants range in small limits, constituting an average of 3-7 MK (thickness 1-3 MK). Larger chloroplasts at higher plants are rare. For example, Selaginell (plauenovoid) in the cells of the leaf leaf are one or two large chloroplasts of a plate form. The magnitude and form of chloroplasts change depending on external conditions. In plants, the chloroplasts are generally larger than that of light-loving, and, as a rule, are rich in chlorophyll. Typically, the cell carries a large number of chloroplasts, and their number changes greatly; On average, it consists of 20 to 50 chloroplasts. Especially rich in chloroplasts leaves, as well as young immature fruits. The total number of chloroplasts in the plant may be enormous; For example, in an adult tree there are dozens and hundreds of billions of chloroplasts. The number of chloroplasts in the cage is associated with their magnitude. So, in corn in the cells of the leaves is usually contained several chloroplasts, but at varieties with especially large chloroplasts the number of them in the cell is reduced to two.

In many lower plants (algae) shape, number and dimensions of chloroplasts are very diverse. They can have a lamellar form (Mougeotia), starfish (Zygnema) or be in the form of a spiral tape (spirogyra) and ribbed cylinders (Closterium). Such chloroplasts are usually very large, found in a cell in a small amount (from one to several) and are called chromatophoras. But also in algae, chloroplasts of the usual lenside form can occur, and in this case the number of them in the cell is usually large.

In the cells of higher plants, chloroplasts are located in a cytoplasm in such a way that one of their flat sides is drawn to the cage shell, and there are especially many of them near the interclausers filled with air. Here they are closely adjacent to each other and the outlines are becoming angular. However, the position of chloroplasts in the cell may vary depending on the external conditions and above all the illumination. They are located in a cage so that the light is tracked in the best way, without exposing at the same time the expansion of direct sunlight. In the leaves of some plants at the scattered light, chloroplasts are located preferably on the walls of the cell shell, which are addressed to the surface of the organ, in the bright light they focus on the side walls or turn to the rays with a narrow side, i.e. the edge. The same movement of chloroplasts is sometimes observed and under the influence of other stimuli - temperature, chemical, mechanical, etc. Is the movement of the plastic active or passive (current cytoplasm), it is not yet fully clarified, but currently more arguments in favor of active movement.

Based on the complexity of photosynthesis processes consisting of a number of reactions, each of which is catalyzed by a special enzyme, it can be assumed that chloroplasts have an ordered and complex structure. And indeed, in the usual light microscope, it is often seen that chloroplasts are not completely homogeneous, and they have more dark small grains, oriented parallel to the surface of the chloroplast, which were named granov. Studies using an electron microscope confirmed the existence of the Grand Prix and showed that the entire chloroplast in general and the granas have a complex structure.

Like mitochondria, chloroplasts are membrane structures that are freely lying in the cytoplasm. From the cytoplasm, they are selected by a two-paved shell with a clearly visible light gap between membranes. These membranes, as suggesting, are smooth and do not contain attached particles. Until recently, they believed that the sheath of chloroplasts was solid, no holes and that its membranes are not connected to the membranes of the endoplasmic network. But now the data showing that it is not always the case. Sometimes submicroscopic holes may occur in separate places. It is possible that these "pores" can be in close contact with the endoplasmic network in certain periods of the chloroplasts, but this contact is short-lived. Chloroplast shell, possessing the property of selective permeability, plays a regulatory role in the exchange of substances between cytoplasm and chloroplast.

The body of chloroplast is permeated with a system of two-grained plates, called lammella. The space between the lamella is filled with a water-protein liquid - stroma, or chloroplast matrix. In the stroma can be starchy grains, oil droplets and ribosoma particles. Most recently, with the help of particularly thin methods of preparation of drugs in the stroma of chloroplasts of some plants, the accumulations of parallel fibrils with a diameter of 80-100 Å and more than 1000 Å long were detected. These bunches of chloroplast microfbrills got a name stromcentrov. Their function is completely unclear.

In some sections of chloroplast, the lamella are quite tightly suitable for each other, located parallel to its surface, as a result of which the lamella clusters called the granas are formed in these sites. Inside the marriage paired lamel membranes merge along the edges, forming closed flatted bags, called disks, or tylacoids. Packs of such disks and form a grana. Separate marriage are interconnected into a single system with a lamella, penetrating intergregated spaces. Chlorophyll does not diffuse diffuse in chloroplast, and focuses in the lamellah, as they suggest, in the form of a monomolecular layer. Ribosomes are not only in the matrix, but can occur on the surface of the Grand Prix.

The number of grank discs ranges from two to several tens, and the diameter depending on the type of plant - from 0.3 to 2 MK. Therefore, many plants are not visible in the light microscope. The number and location of the Gran in chloroplast depends on the type of plant, age and activity of chloroplasts. In the Aspidistra chloroplasts, the Grand is so many that they come into contact with each other, and in the so-called pumpkin satellite cells the bulk of chloroplast is busy with stroma. In chloroplasts of tomato leaves and chrysanthemums, the grana randomly scattered, and in chloroplasts of tobacco they are correctly oriented towards the surface of the chloroplast and are located at an equal distance from each other. In light-lubricant plants, the grain is smaller than at the trendy.

The structure of chloroplasts of higher plants is perfectly adapted to their execution main function - Photosynthesis. Already the separation of chlorophyllon apparatus on fine plaststs means a huge increase in the active surface. Due to the formation of membranes and the Grand Prix, this surface increases even more. A large active surface and a thin spatial orientation provide easy access of the energy of the light quantum and the possibility of transferring this energy to chemical systems involved in photosynthesis. The principle of closed chambers - thylakoids, due to the spatial separation, it allows you to simultaneously and independently carry out the same complex of reactions constituting photosynthesis. In the ribosomes of chloroplasts there is a protein synthesis.

In the cells of some algae (spirohyra) and less often of higher plants (for example, the cells of the so-called plating of conductive beams in the corn) there are marched chloroplasts, in which the lamellas permeate the stroma without forming a distinct Grand Prix.

The origin and development of chloroplasts studied still very little and a single point of view on this issue does not yet exist. It is known that in young, embryonic cells of differentiated chloroplasts. Instead there are so-called proplastids. These are very small (the shares of the micron) of the Taurus, located on the verge of the resolution of the light microscope. Initially, they have an amoebolic form (carry the blades), are excluded from the cytoplasm of the double membrane and do not contain internal membranes or chlorophyll. Internal membranes forming lamellas develop later. There are several hypotheses about the further development of gaylastide. According to one of them, in the transparent stroma of the propellastides, the clusters of the smallest bubbles are formed, located in the correct order like the crystal lattice. This accumulation of bubbles, each of which dresses its own membrane, is called primary granu. On the periphery of the primary grain there are lamellas that spread in all directions from it. In the future, all the lamellar structures of chloroplast are formed, including the marriages. In the light of them there is a deposition of pigments and, above all, chlorophyll.

According to another hypothesis, the lamellas are initially formed as the folds of the inner membrane of the shell of the propellastides, and not from the bubbles. At the same time, a structure similar to mitochondria occurs first.

Thus, these hypotheses proceed from the principle of continuity of the plastic and deny their origin from other organides of the protoplast and, above all, from the cytoplasm. However, other scientists believe that mitochondria and plastists on origin are closely related to each other. For example, we managed to show the occurrence of mitochondria from mature chloroplasts by "boring". Subsequently, these mitochondria could again unite with chloroplasts. But all these hypotheses did not receive a sufficient justification, and the question of the origin of the plastic is still waiting for its decision.

In addition to the occurrence of preciposteids, chloroplasts can multiply by simple division. In this case, two subsidiaries are formed from an adult chloroplast, often unequal sizes. The electronic microscopic picture of this division has not yet been studied.

The structure of chloroplast does not remain constant, it naturally changes in the process of cell growth. The change in the structure of chloroplasts with the age of the leaves is noticeably even in the light microscope. Thus, the young leaves usually correspond to the fine-harmonary structure, middle-aged leaves - largest structure. In aging leaves, there is a violation of the structure and degradation of chloroplasts.

Chloroplasts are rather tender fragile organoids. When placing a cell in distilled water or a hypotonic saline solution, they quickly burst, bubble swollen are formed on their surface, and then they are blurred. Electronic microscopic studies have shown that swelling occurs in stroma, and not in lamella. In case of damage to the cell, chloroplasts considered in a normal microscope, first become rumbling, swell, acquire a foamy look and, finally, the granularity disappears. Pathological changes occur in chloroplasts of leaves and with a shortcoming in the soil of mineral nutrition. However, chloroplasts of some cells can detect high resistance. So, in the trees, the green color of the crust is due to the presence of a layer of cells with chloroplasts. These chloroplasts perfectly carry low temperatures and go to the active state, detected by severe greening of the cortex, for example, in aspen, very early in the spring when there are severe frosts at night. Low winter temperatures also transfer chloroplasts of leaves (needles) of our evergreen coniferous trees. At the same time, as shown electronic microscopic studies, they retain their complex internal organization.

Leukoplasts

These are small colorless plaststs. Their light microscope is often difficult to detect, as they are colorless and have the same refractive index as cytoplasm. You can only detect them in the case of the accumulation of large inclusions within them. This is very gentle organides and in the preparation of sections of a living material are even more easily destroyed than chloroplasts. They are found in adult cells hidden from sunlight: in roots, rhizomes, tubers (potatoes), seeds, stalk core, as well as in cells exposed to strong light (skin cells). Often, the leukoplasts are collected around the core, surrounding it sometimes from all sides. The form of leukoplasts is very impermanent, most often it is spherical, egg-shaped or spindlers.

The leukoplasts are organides associated with the formation of spare nutrients - starch, proteins and fats. The activity of leukoplasts is specialized: some of them accumulate mainly starch (amyloplasts), others - proteins (proteoplasts, also called aliaronoplasts), third - oils (oleoplasts). The leukoplasts of cells of the skin of the leaves and stalks cannot be attributed to any of these types, since the function is not yet clarified.

Amyloplasts Across starch in the form of so-called starchy grains. This is the predominant type of leukoplasts. The structure of amyloplasts and the mechanism of formation of starch is difficult to study in the light microscope, and in the electron microscope it is still weakly studied. As suggested, they are formed from the gaylastide, but in contrast to chloroplasts, the development of their structure does not go far away, but is delayed at a fairly early stage - the stages of immature, weak-skinned plasts. Outside, amyloplasts are selected by a two-membrane shell. Inside the plastic is filled with fine-grain stroma. The formation of starch grains in amyloplasts is preceded by the development of the smallest bubbles, which merge, are suggested, limiting the membrane of the stroma section in the center of the plastic. This area called educational Center, it becomes lighter, reminding vacuole. In the educational center and the starch deposition begins. When the future starch grain begins to increase in size, the membranes, the separation of the educational center disappear, in the future the growth of grain is out of connection with them. With the deposition of starch, the amyloplast and stromas sheath can be strongly stretched, as a result of which the size of the amyloplast is greatly increased due to the growing starch grain. The starch grain is then filled with almost the entire cavity of the amyloplast, pushing its living contents to the periphery in the form of the finest film on the grain surface. In many cases, the starch grain can achieve such dimensions that the amyloplast is broken and remains only on one side of the starch grain. In this case, new portions of starch can synthesize only in those areas where the starch grain remains in contact with membranes and a stroma amaloplast.

Developing from precipulatide, amyloplasts under certain conditions can be transformed into plasts of other types. If, for example, put the root barley on the light, then it can be seen that some leukoplasts increase in volume and turn into chloroplasts similar to those that are formed in the leaves. If such a root again deprive the light, then these chloroplasts decrease in size and lose their chlorophyll, but do not turn into leucoplasts again, and globals (ballotine balls)) produce thus chromoplasts. Oleoplasts, i.e., leukoplasts that form mainly oils are much less common than amyloplasts (for example, in some single-dollar leaves cells). They usually represent the aging product of chloroplasts that are losing chlorophyll. In this case, the smallest oil globules arise in the stroma of the plasts. Then the plastic shell is destroyed, and the contents of the adjacent plastids merge, forming larger fat drops. Sometimes starch accumulates in such plastids.

Synthesis of spare protein - protein - can be carried out in the third type of leukoplasts - proteoplasts. The protein in the form of crystals and grains is formed in the seeds of many plants, especially those that contain a lot of oil (for example, ticklaith seeds). Proteoplasts, like amylocklasts, arise from a precipitide. Their development is also delayed at the stage of immature lamellar plasts. In the stroma proteoplast spare protein, initially accumulates in the form of fibrils, which are then combined into larger beams. Next, the shell and stromrom of the plasts are destroyed, and protein fibril bundles are converted into the likeness of small viscous vacuoles. Then vacuoles of adjacent plates merge, part of the protein is made in the form of crystalloids.

Thus, the starch, and spare protein, and the drops of oil are inert inclusions, livestock products of the plastic. Moreover, each of them can accumulate not only in leucoplasts, but also in chloroplasts and chromoplasts. But if the starch is formed in plastids, then spare proteins and fats can very often have and unscheduled origin, it is probably directly in the cytoplasm and regardless of the plastic. Structural processes occurring at the same time, weakly studied.

Chromoplasts

Chromoplasts are plasts of yellow or orange and even red. They are found in the cells of many petals (dandelion, buttercup, bow), mature fruit (tomatoes, rosehip, rowan, pumpkin, watermelon, orange), rooteplood (carrots, fodder beet). The bright color of these organs is due to yellow and orange pigments - carotenoids focused in chromoplasts. These pigments are also characteristic of chloroplasts, but they are masked by chlorophyll. They are not soluble in water, but soluble in fats.

Unlike chloroplasts, the shape of chromoplasts is very modified and determined by their origins and the state of pigments, as well as systematic position The forming of their plant. Depending on the state of carotenoids, chromoplasts of three types are distinguished:

1. chromoplasts in which carotenoids are deposited in the form of small, but visible in the light microscope with no bound crystals (chromoplasts of carrots);
2. chromoplasts, in which carotenoids are dissolved in submicroscopic lipoid globules (petals of buttons and aloe);
3. chromoplasts, the carotenoids of which are collected in bundles consisting of submicroscopic threads and associated protein fibrils (red pepper, tomatoes, mandarin).

In contrast to chloroplasts and leukoplasts, chromoplasts rarely occur directly from the precipoxide, and usually represent the result of chloroplasts degeneration. The exceptions are chromoplasts of carrots, which occur not from chloroplasts, but from leucoplasts or directly from the propellastide. Parts of the root, not immersed in the soil and developing in light, are usually green. This is not due to the conversion of chromoplasts into chloroplasts, but due to the formation of chloroplasts from preciposses or leucoplasts. Chromoplasts can not turn into other types of plastic. Most often, chromoplasts are formed in the destruction of chloroplasts, when the latter enter into an irreversible phase of development. This is the origin of chromoplasts of the 2nd and 3rd types. At the same time, in chloroplasts, the content of fats and carotenoids increases, which are assembled in the stroma plastis in the form of submicroscopic globul, lamellar structures disappear, and chlorophyl is destroyed. Pigment globules grow, and the volume of stroma decreases, as a result of globules can fill most of the plasts. The round form of the "maternal" chloroplast is preserved. Such a process of degradation of chloroplasts occurs, probably, with the autumn yellowing of the leaves and in the ripening of fruits. Chlorophyll in yellowing leaves is destroyed and ceases to mask carotenoids, which sharply perform and determine the yellow color of the leaves.

In the root plates of carrots, chromoplasts arise from the leukoplasts, initially starchy, while carotenoids are accumulated in the stroma plastids, which are later crystallized. Starch disappears as the concentration of carotene grows, the plastic mass decreases and it becomes difficult to detect it. The crystallized pigment is the dominant of the chromoplast dominant in volume, so the form of chromoplast ultimately is determined by the form of crystallizing pigment and is usually incorrect: toothed, sickle, needle or lamellar. Plates may have the outlines of the triangle, rhombus, a parallelogram, etc.

The figure shows one of the watermelon cells with a raspberry pulp when viewed in a light microscope. The cage shows a cytoplasm consisting of thin threads, stretched in different directions. In more massive covers of the cytoplasm there are needle crystals of the pigment of chromoplasts. The largest cluster of crystals is observed near the nucleus. In another variety of watermelon with the flesh, the pigment of chromoplasts is crystallized not only in the form of needle crystals, but also short prisms of various sizes.

The value of chromoplasts in the exchange of substances is clarified very little. Like leukoplasts, they are deprived of the ability to photosynthesis, as they do not contain chlorophyll. The indirect value of chromoplasts is that they determine the bright color of flowers and fruits, attracting insects for cross-pollination and other animals - for the spread of fruits.

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Lecture number 6.

Number of hours: 2

Mitochondria and plasts

1.

2. Plasts, structure, varieties, functions

3.

Mitochondria and plastists - two-grained eukaryotic cell organides. Mitochondria is found in all cells of animals and plants. Plastics are characteristic of plant cells that carry out photosynthetic processes. These organoids have a similar structure of the structure and some general properties. However, according to the main metabolic processes, they differ significantly from each other.

1. Mitochondria, Building, Functional Value

general characteristics Mitochondria. Mitochondria (Greek. "Mitos" - thread, "chondrion" - grain, granule) - rounded, oval or row-shaped two-membrane organoids with a diameter of about 0.2-1 microns and up to 7-10 μm long. These organoidsit is possible to detect with light microscopy, as they have sufficient magnitude and high density. The features of the internal structure can be studied only with the help of an electron microscope.Mitochondria was opened in 1894 by R. Altman, who gave them the name "Borrowers".The term "mitochondria" was introduced by K. Benda in 1897. Mitochondria is availablepractically All eukaryotic cells. Anaerobic organisms (intestinal amubs, etc.) are missing mitochondria. Numbermitochondria in the cage ranges from 1 to 100 thousand.and depends on the type, functional activity and age of the cell. So in the vegetable cells mitochondria less than in animals; A B. Young cells are more than in older.The life cycle of mitochondria is several days. The mitochondria cell usually accumulates near the cytoplasm areas, where the need for ATP arises. For example, in the heart muscle of mitochondria are located near Miofibrils, and in silence form a spiral case around the flashes axis.

Ultramicroscopic structure mitochondria. Mitochondria is limited to two membranes, each of which has a thickness of about 7 nm. The external membrane from the inner separates the intermogram space of about 10-20 nm wide. The outer membrane is smooth, and the internal forms folds - Crysta (Lat. Crysta - Comb, grown), increasing its surface. The number of Crysta is different in the mitochondria of different cells. They can be from several tens of up to several hundred. Especially a lot of Cryst in the mitochondria of actively functioning cells, such as muscle. In Crystas, there are chains of transfer of electrons and associated phosphorylation ADP (oxidative phosphorylation). The internal space of mitochondria is filled with a homogeneous substance called the matrix. Mitochondrial cristes are usually completely not completely brazed by the mitochondria cavity. Therefore, matrix throughout is continuous. The matrix contains the Ring DNA molecules, mitochondrial ribosomes, there are deposits of calcium and magnesium salts. On mitochondrial DNA, the synthesis of RNA molecules of various types, ribosomes are involved in the synthesis of a number of mitochondrial proteins. Small DNA dimensions Mitochondria do not allow to encode the synthesis of all mitochondrial proteins. Therefore, the synthesis of most proteins mitochondria is under nuclear control and is carried out in the cytoplasm of the cell. Without these proteins, the growth and operation of mitochondria is impossible. Mitochondrial DNA encodes structural proteins responsible for proper integration in the mitochondrial membranes of individual functional components.

The reproduction of mitochondria. Mitochondria is multiplied by dividing with a haunted or fragmentation of large mitochondria into smaller. Mitochondria formed by this way can grow and share again.

Mitochondrial functions. The main function of mitochondria is in the synthesis of ATP. This process occurs as a result of the oxidation of organic substrates and phosphorylation ADP. The first stage of this process occurs in the cytoplasm in anaerobic conditions. Since the main substrate is glucose, the process is called glycolize. At this stage, the substrate is subjected to enzymatic cleavage to peyrogradic acid with simultaneous synthesis of a small amount of ATP. The second stage occurs in mitochondria and requires the presence of oxygen. At this stage, there is a further oxidation of peyrogradic acid with the release of CO 2 and the transfer of electrons to acceptors. These reactions are carried out using a row of tricarboxylic acid cycle enzymes that are localized in mitochondria matrix. The electrons released during the oxidation in the oxidation process are transferred to the breathing circuit (electron transfer circuit). In the respiratory chain, they are connected to molecular oxygen, forming water molecules. As a result, the energy that is covered in the form of ATP is released in small portions. Complete oxidation of one glucose molecule to form carbon and water dioxide and provides energy to reload 38 ATP molecules (2 molecules in cytoplasm and 36 in mitochondria).

Analogues of mitochondria in bacteria. There are no mitochondria bacteria. Instead, they have electrons transfer chains localized in the cell membrane.

2. Plasts, structure, varieties, functions. The problem of origin of the plastic

Plasts (from. Greek. plastides. - Creating, forming) - It is two-grained organides characteristic of photosynthetic eukaryotic organisms.Three main types of plastic are distinguished: chloroplasts, chromoplasts and leukoplasts.A combination of plastic in a cell called plastic. The plastides are interconnected by a single origin in ontogenesis from the precipoxes of meristematic cells.Each of these types under certain conditions can move one to another. Like mitochondria, the plastids contain their own DNA molecules. Therefore, they are also able to multiply regardless of cell division.

Chloroplasts(from Greek. "chloros."- Green,"plastos."- Flare) - These are the plastids in which photosynthesis is carried out.

The overall characteristic of chloroplasts. Chloroplasts are green organides with a length of 5-10 μm and 2-4 microns width. In green algae there are giant chloroplasts (chromatophores), reaching lengths of 50 microns. Higher Plants Chloroplasthave two-way or ellipsoid shape. The number of chloroplasts in the cell can vary from one (some green algae) to a thousand (mahorka). IN The cage of higher plants on average 15-50 chloroplasts are located.Typically, chloroplasts are uniformly distributed over the cytoplasm of the cell, but sometimes they are grouped near the kernel or cell shell. Apparently, it depends on external influences (lighting intensity).

The ultramicroscopic structure of chloroplasts. From cytoplasm, chloroplasts are separated by two membranes, each of which has a thickness of about 7 nm. There is an intermambrane space between the membranes with a diameter of about 20-30 nm. The outer membrane is smooth, the inner has a folded structure. Between the folds are located tylacoidshaving a view of the disks. Tylacides form stacks like a coin column called granas. M.miscellaneously connected by other thylacoids ( lamella, Froet.). The number of thylacoids in one grain varies from several pieces to 50 or more. In turn, in the chloroplastic of higher plants there is about 50 Grand Prix (40-60) located in a checker order. This arrangement provides maximum illumination of each garbranch. In the center of the Grand is chlorophyll, surrounded by a layer of protein; Then there is a layer of lipoids, again protein and chlorophyll. Chlorophyll has a complex chemical structure and exists in several modifications (a, B, C, D ). Higher plants and algae as the main pigment contains xlaurophyll and with a formula with 55 H 72 o 5N 4 m g . As an additional contains chlorophyllb. (Higher plants, green algae), chlorophyll with (brown and diatoms algae), chlorophylld. (Red algae). Chlorophyll formation occurs only in the presence of light and iron that plays the role of the catalyst.The chloroplast matrix is \u200b\u200ba colorless homogeneous substance that fills the space between tylacoids.In the matrix are locatedthe enzymes of the "dark phase" of photosynthesis, DNA, RNA, ribosomes.In addition, in the matrix there is a primary deposition of starch in the form of starch grains.

Properties of chloroplasts:

· semi-autonomy (have their own whiteoxitheating apparatus, but most of the genetic information is in the kernel);

· ability to independently movement (go from direct sunlight);

· ability to independent reproduction.

Reproduction of chloroplasts. Chloroplasts develop from precipitide, which are able to replicate by division. Higher plants also meet the division of mature chloroplasts, but extremely rare. When aging the leaves and stems, the ripening of fruit chloroplasts lose the green color, turning into chromoplasts.

Functions of chloroplasts. The main function of chloroplasts is photosynthesis. In addition to photosynthesis, chloroplasts carry out the synthesis of ATF from ADF (phosphorylation), synthesis of lipids, starch, proteins. In chloroplasts, enzymes are also synthesized, providing the light phase of photosynthesis.

Chromoplasts(from Greek. Chromatos - color, paint and "plastos. "- Flare)- These are painted plasts. Their color is due to the presence of the following pigments: carotene (orange-yellow), lycopene (red) and xanthofilla (yellow). Chromoplasts are especially many in the cells of petals of flowers and the shells of fruits. Most of all chromoplasts in fruits and fading flowers and leaves. Chromoplasts can develop from chloroplasts, which are losing chlorophyll and accumulate carotenoids. This happens when many fruits are matured: pouring ripe juice, they turn yellow, pink or blushing. The main function of chromoplasts is to ensure coloring of flowers, fruits, seeds.

In contrast to leucoplasts and especially chloroplasts, the inner membrane of chloroplasts does not form thylacoids (or forms single). Chromoplasts are the final result of the development of the plastic (chromoplasts and plastists turn into chromoplasts).

Leukoplasts(from Greek. Leucos - White, Plastos - Wailed, Created). These are colorless plastsrounded, ovoid, spindle-shaped. Located in underground parts of plants, seeds, epidermis, stem core.Especially rich potato tuber leukoplasts. The inner shell forms a few thylacoids. Chloroplasts are formed on the light of chloroplasts.Leukoplasts in which the secondary starch is synthesized and accumulated amyloplastami, oil - eylaloplastami, proteins - proteoplasts.The main function of the leukoplasts is the battery of nutrients.

3. The problem of origin mitochondria and plastic. Relative autonomy

There are two main theories of origin of mitochondria and plastic. These are the theories of direct form and consecutive endosimbitosis. According to the theory of direct form of mitochondria and plastdoms formed by the corporation itself. Photosynthetic eukaryotes occurred from photosynthesising prokaryotes. At the resulting autotrophic eukaryotic cells, mitochondria was formed by intracellular differentiation. As a result, animals and mushrooms occurred as a result of loss of plastic from autotrophic.

The theory of consecutive endosimbitis is the most reasonable. According to this theory, the emergence of the eukaryotic cell passed through several stages of symbiosis with other cells. At the first stage of the cell type of anaerobic heterotrophic bacteria included free-natured aerobic bacteria that turned into mitochondria. In parallel, this in the host cell of the prokaryotic gene is formed into a core separated from the cytoplasm. In this way, the first eukaryotic cell occurred, which was heterotrophic. The emerging eukaryotic cells by repeated symbiosis included cineural algae, which led to the appearance of chloroplasts like structures. Thus, mitochondria has already been in heterotrophic eukaryotic cells, when the latter as a result of symbiosis has acquired plasts. In the future, as a result of the natural selection of mitochondria and chloroplasts lost part of the genetic material and turned into structures with limited autonomy.

Evidence of endosimbiotic theory:

1. The similarity of the structure and energy processes in bacteria and mitochondria, on the one hand, and in silneur algae and chloroplasts, on the other hand.

2. Mitochondria and plastists have their ownspecific system of protein synthesis (DNA, RNA, Ribosomes). The specificity of this system lies in autonomy and sharp difference from that in the cell.

3. DNA mitochondria and plastic isa small cyclic or linear molecule, which differs from the DNA of the nucleus and in its characteristics is approaching DNA of prokaryotic cells.Synthesis DNA mitochondria and plastic notdepends on the synthesis of nuclear DNA.

4. In mitochondria and chloroplasts there are also RNAs, T-RNA, P-RNA. Ribosomes and p-RNA of these organoids differ sharply from those in the cytoplasm. In particular, the ribosomes of mitochondria and chloroplasts, in contrast to the cytoplasmic ribosoma, are sensitive to the antibiotic chloramphenicol, overwhelming protein synthesis in prokaryotic cells.

5. The increase in the number of mitochondria occurs by the growth and division of the initial mitochondria. An increase in the number of chloroplasts occurs through changes in the props, which, in turn, multiply by division.

This theory well explains the preservation of the mitochondria and the remains of the residual replication systems and allows you to construct consistent philogeneization from prokaryotes to eukaryotes.

Relative autonomy of chloroplasts and plastids. In some respects, mitochondria and chloroplasts behave like autonomous organisms. For example, these structures are formed only from the initial mitochondria and chloroplasts. This was demonstrated in experiments on plant cells, in which the formation of chloroplasts was suppressed by antibiotic streptomycin, and on yeast cells, where mitochondrial education was suppressed by other drugs. After such influences, the cells have never been restored missing organelles. The reason is that mitochondria and chloroplasts contain a certain amount of its own genetic material (DNA), which encodes part of their structure. If this DNA is lost, which occurs when the formation of the formation of organelle is suppressed, the structure cannot be recreated. Both types of organelles have their own protein-synthesizing system (ribosomes and transport RNA), which is somewhat different from the main protein-synthesizing cell system; It is known, for example, that the protein-synthesizing system of the organelle can be suppressed by antibiotics, while they do not act on the main system. DNA Organelles is responsible for the main part of non-chromosomal, or cytoplasmic, heredity. Extcomic heredity is not subject to Mendelle law, since when dividing the cells of DNA, the organelle is transmitted to child cells otherwise than chromosome. The study of mutations that occur in the DNA of the Organelle and DNA chromosomes showed that the DNA of the Organelle is only responsible for the small part of the organization of the Organell; Most of their proteins are encoded in genes located in chromosomes. The relative autonomy of mitochondria and plastid is considered as one of the evidence of their symbiotic origin.