The main ways of respiratory metabolism of plants. Respiratory substrates and respiratory quotient. Respiration substrates and respiratory quotient

Breath - one of the most important metabolic processes of a plant organism. The energy released during respiration is spent both on growth processes and on maintaining the plant organs that have already completed growth in an active state. However, the significance of breathing is not limited to the fact that it is a process that supplies energy. Respiration is like photosynthesis complex redox process going through a series of steps. At its intermediate stages, organic compounds are formed, which are then used in various metabolic reactions. Intermediate compounds include organic acids and pentoses, which are formed during different pathways of respiratory decomposition. Thus, the respiratory process is a source of many metabolites.

Despite the fact that the process of respiration in its total form is opposite to photosynthesis, in some cases they can complement each other.

Both processes are suppliers of both energy equivalents (ATP, NADPH) and metabolites. As can be seen from the overall equation, water is also formed during respiration. This water, under extreme conditions of dehydration, can be used by the plant and protect it from death. In some cases, when the energy of respiration is released in the form of heat, respiration leads to a useless loss of dry matter. In this regard, when considering the process of respiration, it must be remembered that the intensification of the process of respiration is not always beneficial for the plant organism.

The individual stages of respiration are carried out in different parts of the plant cell. This is determined by the distribution of enzymes in individual organelles with their characteristic metabolic functions. The study of localization, topography of enzyme systems has great importance and to understand the interaction of individual parts of the cell, as well as the possibility of interaction of individual metabolites.

Concentrated in the cytoplasm enzymes that catalyze the process of glycolysis and the pentose phosphate pathway. There is evidence that glycolysis enzymes are also present in the mitochondrial matrix. The enzymes of the Krebs cycle are concentrated mainly in the mitochondrial matrix. Enzymes of the respiratory chain are woven in a certain sequence into the inner membrane of mitochondria. Approximately 20-25% of the total protein of the inner membrane of mitochondria are enzyme proteins involved in the transfer of protons and electrons. It is assumed that carrier enzymes are grouped so that each group represents an independent unit - the respiratory ensemble. In mitochondria, there can be several thousand of such ensembles, which are evenly distributed in membranes.

In inner membrane of mitochondria the enzymes providing the process of phosphorylation (ATP synthase) are also localized. The ATP carrier is also concentrated there. Due to this, the ATP formed in the mitochondria can leave them and be used in other parts of the cell. At the same time, the same transporter transports ADP into the inner space of mitochondria. Pyruvic acid and some organic acids of the Krebs cycle also penetrate the inner membrane. The specific transporter carries out the transfer of phosphation into the mitochondria. However, for the coenzymes NAD and NADP and some other substances, the inner membrane is impermeable.

Part of the nicotinamide coenzymes is restored in the cytoplasm during glycolysis. In order to carry out their oxidation, there are special mechanisms. In plants, NADH dehydrogenase, under the action of which NADH can enter the respiratory chain, is localized on the outer surface of the inner membrane. In the absence of external NADH dehydrogenase, the transfer of NADH to the inner membrane is carried out using a shuttle mechanism. The essence of this mechanism is as follows. NADH formed in the cytoplasm reacts with phosphodioxyacetone, reducing it to glycerophosphate. Glycerophosphate penetrates the membrane and donates hydrogen to flavin dehydrogenase and through it into the respiratory chain. At the same time, glycerophosphate is again converted into phosphodioxyacetone, which leaves the mitochondria into the cytoplasm and again undergoes the reduction of NADH + H+. A similar mechanism for the transfer of energy equivalents across membranes was also found in chloroplasts. Thus, in the cell at the same time both the distribution of substances in different compartments and the relationship between them.

An important question is how provides energy for the processes occurring in the nucleus of the cell. Apparently, ATP partially enters the nucleus from the cytoplasm. The nucleus also has its own respiratory enzymes. Thus, the enzymes of glycolysis were found in the nucleoplasm. There is evidence that enzymes of the respiratory chain, similar to mitochondrial ones, function in the nucleus. Finally, respiratory enzymes have also been found in chloroplasts.

plant respiration substrates

In the works of I.P. Borodin (1876) showed that the intensity of the respiration process is directly proportional to the content of carbohydrates in plant tissues. This gave grounds to assume that carbohydrates are the main substance consumed during respiration (substrate). In finding out this issue the determination of the respiratory coefficient is of great importance. Respiratory quotient (RC)- this is the volume or molar ratio of CO2 released during respiration to CO2 absorbed over the same period of time. With normal access to oxygen, the DC value depends on the substrate of respiration. If carbohydrates are used in the process of respiration, then the process proceeds according to the equation

С6Н1206 +602 -> 6С02 + 6Н20.

In this case DC equal to one: 6С02/602 = 1.

However, if more oxidized compounds, such as organic acids, are decomposed during respiration, oxygen uptake decreases, and DC becomes greater than unity. So, if malic acid is used as a breathing substrate, then DC = 1.33.

The determination of the respiratory coefficients of different plant tissues shows that under normal conditions it is close to unity. This gives reason to believe that the plant primarily uses carbohydrates as a respiratory material. With a lack of carbohydrates, other substrates can be used. This is especially evident in seedlings that develop from seeds, which contain fats or proteins as a reserve nutrient. In this case, the respiratory coefficient becomes less than one. When used as a respiratory material, fats are broken down into glycerol and fatty acids. Fatty acids can be converted to carbohydrates through the glyoxylate cycle. The use of proteins as a substrate for respiration is preceded by their breakdown into amino acids.

2. From the scientists proposed below, the position (theory) about genetic

3. The most traditional substrates for respiration in plants are ...

8. In the process of breaking down one molecule of glucose to carbon dioxide

9. Oxygen splitting compared to anoxic in terms of energy ...

10. When carbohydrates are broken down, the greatest amount of ATP is synthesized ...

11. When one glucose molecule is broken down to pyruvic acid, it is additionally formed in the cell ...

12. Phosphorylation is the process of electron transfer along the respiratory chain, which goes with the formation ...

13. The largest number Energy is released when oxidized...

2) microorganisms that decompose 4) plants that prefer the pyroorganic substances of the soil with the absorption of ammonium nitrogen. release of ammonia;

4. The conditional boundary between macroelements and microelements is determined

5. The reduction of nitrites to ammonium in the cell is carried out by the enzyme ...

10. In symbiotic nitrogen fixation, the source of energy for the breakdown of nitrogen molecules is ...

11. The reduction of nitrates to ammonium in plants is carried out ...

15. A sign of potassium deficiency is ...

17. The composition of the catalytic centers of many redox enzymes (cytochromes, catalase, peroxidase) includes ...

18. The composition of the catalytic centers of polyphenol oxidase and ascorbate

19. Cobalt is part of vitamin B12, which is necessary for the process of molecular nitrogen fixation. The most sensitive to the lack of cobalt is ...

Growth and development

8. What is the name of the irreversible growth movements of plants caused by a unilaterally acting factor?

9. What event in the growth zone of a root or stem, according to the Kholodny-Vent theory, is primary?

10. What are the names of plant rhythms with a period of about a day, which are endogenous in nature?

11. What are the reasons for the sharp decrease in growth rates in plants with a lack of water?

12. Which of the following signs are characteristic of etiolated

13. What type of tropisms does the movement of a wheat straw rising after lodging refer to?

14. What environmental factors are the main ones during the transition

2. What is the reason for the death of heat-loving plants at low positive temperatures?

3. What are the causes of plant death at low negative temperatures?

9. Why the use of fertilizers contributes to a more successful transition

10. What are the characteristics of plants grown from seeds treated for an hour with a 3% sodium chloride solution?

9. BRIEF INFORMATION ON THE FORMATION OF PLANT PHYSIOLOGY AND ON SCIENTIFIC PHYSIOLOGISTS

Plant physiology originally developed as component botany. The beginning of experimental plant physiology was laid by the experiments of the Dutch naturalist Jan Van Helmont. In 1629 he conducted the first physiological experiment, studying the nutrition of plants. He placed soil weighing 91 kg in an earthen vessel and planted a willow branch in it, the weight of which was 2.25 kg, and regularly watered it with rainwater. After 5 years, I separately weighed the soil and the branch. It turned out that the willow weighed 77 kg, and the weight of the soil decreased by only 56.6 g. Based on this experience, Helmont concluded that the mass of the plant consists of water. This is how water theory nutrition.

The stages of further development of plant physiology were associated with the discovery of photosynthesis. In 1771, Joseph Priestley discovered that mint plants placed in a vessel corrected the air in it, spoiled by the burning of a candle.

The Swiss botanist Jean Senebier in 1800 published the treatise "Physiology of Plants", in which he first defined the subject and tasks of plant physiology as an independent science and gave the name to this science.

Also, the main stages in the development of plant physiology are associated with the study of growth movements - tropisms (C. Darwin), the development of the theory of mineral nutrition (Yu. Liebig, J. B. Bussengo).

IN late XIX - early XX centuries. intensive study of the mechanisms of plant respiration began (V.I. Palladin, A.N. Bakh).

The founders of Russian plant physiology are Andrey Sergeevich Famintsyn and Kliment Arkadyevich Timiryazev. Research by A.S. Famintsyn are devoted to the metabolism and energy of plants. He is the author of the first domestic textbook on plant physiology (1887). The main studies of K.A. Timiryazev on plant physiology are devoted to the process of photosynthesis.

IN In 1934, the Institute of Plant Physiology was established in the system of the USSR Academy of Sciences, which in 1936 was named after K.A. Timiryazev. This institution played an important role in the development of Russian plant physiology. The names of such famous scientists as Anatoly Alexandrovich Nichiporovich are associated with him - the main works on the physiology of photosynthesis, the theory of photosynthetic productivity of plants

And its application in agriculture; Mikhail Khristoforovich Chailakhyan - the author of the hormonal theory of plant development (1937); Raisa

The substrate from a mixture of peat chips and bedding peat is well supplied with air. No matter how wet the substrate is, the roots of the plants still receive enough oxygen for respiration. In addition, peat is difficult to decompose. Even with strong moisture and high temperatures, it is unlikely to rot.[ ...]

Respiration is the most perfect form of the oxidative process and the most effective way receiving energy. The main advantage of respiration is that the energy of the oxidized substance - the substrate on which the microorganism grows - is used most fully. Therefore, in the process of respiration, much less substrate is processed to obtain a certain amount of energy than, for example, during fermentation.[ ...]

Respiration is understood as a process associated with the breakdown of carbohydrates, as a result of which energy is released, which provides metabolism and transport in the plant. Since the kinetics of metabolism and transport has already been described, it is possible to calculate the costs of the substrate for respiration from the known balance ratios. Note that in describing respiration, two stages of chemical energy conversion are combined: the stage of substrate oxidation, during which macroergic bonds of ATP are formed, and the stage of using ATP energy. In addition, the balance equation of respiration takes into account the cost of carbohydrates to provide energy for the process of biosynthesis and transport of organic and inorganic substances. In the process of respiration, carbon dioxide is released, which is partially used in photosynthesis. Its dynamics is described on the basis of balance ratios.[ ...]

The difference in respiration between the two groups of fetuses, according to Helme et al., is probably only relative (see section 1.3.4). Both groups share the same enzymes and respiratory substrates. The reason for the differentiation of the process of respiration lies, apparently, both in unequal cytological changes and in insufficient activity of enzymes of certain reactions.[ ...]

Thus, during respiration, oxygen is the final acceptor of hydrogen. In anaerobes, either organic substrates (fermentation) or inorganic substances, such as nitrates or sulfates ("anaerobic respiration"). It can be seen from the diagram that the most simple and primitive transport of electrons is carried out in most anaerobes due to the lack of enzymes in the electron transport chain capable of transferring electrons along the chain up to molecular oxygen.[ ...]

Throughout the summer, the substrate is kept so moist that a few drops of liquid can always be squeezed out of a handful of it without much effort. High humidity will already make it difficult for the roots to breathe, so after each heavy rain, you need to lower the edge of the film for a while and let the excess water drain.[ ...]

An increase in the rate of respiration in the leaves of several varieties of pepper (Capsicum sp.) infected with a strong strain of the engraving virus can be detected at the time of the onset of visible symptoms, and the high rate of respiration is maintained in the future. The situation is different with the root respiration of diseased plants. The virus did not affect the rate of respiration in those varieties in which it did not cause wilting symptoms. At the same time, during the inoculation of Tabasco pepper, which reacts to infection with the wilt virus, a decrease in the intensity of root respiration occurred 12-24 hours after the root permeability increased (see p. 255). It has been suggested that the decrease in respiration in this case is due to the leakage of substrates and enzyme activators.[ ...]

So, the simplest process of aerobic respiration is presented in the following form. Molecular oxygen consumed during respiration is mainly used to bind hydrogen formed during the oxidation of the substrate. Hydrogen from the substrate is transferred to oxygen through a series of intermediate reactions that occur sequentially with the participation of enzymes and carriers. A certain idea of ​​the nature of the breathing process is given by the so-called respiratory coefficient. This is understood as the ratio of the volume of released carbon dioxide to the volume of oxygen absorbed during respiration (С02:02).[ ...]

Tetrazolium salts have also been used as a substrate for determining dehydrogenase activity in tumor cells (Kraus, 1957), for determining the number of viable BCG bacteria in a vaccine (Eidus e. a., 1958), for vital staining of bacteria (Eidus e. a., 1959 ), to detect heat-resistant microbes in milk (Leali, 1958), when recognizing yeast cells with normal respiratory system and with impaired respiration (Ogur, 1957), etc. With the help of a diagnostic medium containing tetrazolium salts, it is possible to differentiate bacteria of the Pseudomonas group (Selenka, 1958) and phytopathogenic bacteria (Lovrekovich, Klement, 1960).[ ...]

VI Palladin was the first to consider respiration as a series of enzymatic reactions. Oi attached the main importance in the oxidation process to the process of removing hydrogen from the substrate.[ ...]

Carbohydrates are the end product of photosynthesis and a substrate for plant respiration and growth. Known information about the protective role of sugars in the adaptation of plants to adverse environmental conditions (Kolupaev, Trunova, 1992). The aim of our research was to study the content of carbohydrates in barley plants (Hordeum distichum L., Novichok village) depending on the level of mineral nutrition and temperature. In the experiments, we used 3-4-week-old plants grown in a climatic chamber on an aquatic culture at two temperature regimes (day/night) - low (13/8°C) and optimal (22/18°C). Mineral elements were introduced into the medium daily in exponentially increasing amounts to ensure a constant low - 0.05 and high - 0.22 g/g-day growth rate (Ingestad and Lund, 1986).[ ...]

It has now been shown that both the hydrogen of the substrate and the oxygen of the air are activated during respiration.[ ...]

Vonros on the substances used in the process of respiration has long occupied physiologists. Even in the works of I. II. Borodin, it was shown that the intensity of the respiration process is directly proportional to the content of carbohydrates in plant tissues. This gave reason to assume that carbohydrates are the main substance consumed during respiration. In clarifying this issue, the determination of the respiratory coefficient is of great importance. If carbohydrates are used in the breathing process, then the process proceeds according to the equation CeH 120b + 6O2 \u003d 6CO2 + 6H2O, in this case the respiratory coefficient is equal to unity - p \u003d 1. However, if more oxidized compounds, such as organic acids, undergo decomposition during breathing, oxygen uptake decreases, the respiratory coefficient becomes greater than one. When more reduced compounds, such as fats or proteins, are oxidized during respiration, more oxygen is required and the respiratory coefficient becomes less than one.[ ...]

The question of the influence of light on the intensity of respiration has been studied by many physiologists. The solution to this problem is complicated by methodological difficulties. In the light, it is difficult to separate the process of photosynthesis from the process of respiration. It is difficult to distinguish between direct and indirect effects of light. So, photosynthesis takes place in the light, the content of carbohydrates increases - this affects the process of respiration. Nevertheless, the use of the method of labeled atoms made it possible, although not polyostyo, to delimit the process of photosynthesis from respiration. At present, it is believed that the influence of light on the process of respiration is diverse. Under the influence of light, especially short-wavelength blue-violet rays, the intensity of normal dark breathing increases. Activation of respiration by light is well shown in chlorophyll-free plants. It is possible that Svot activates oxidase enzymes. Light can have an indirect effect on the respiration of green plants due to the fact that the process of photosynthesis takes place. In turn, the influence of photosynthesis on respiration can be different and even opposite. So, on the one hand, in the process of photosynthesis, the main substrates of respiration, carbohydrates, are formed. Together with t[ ...]

Scheme 1 (Table 36) shows the transport of electrons during respiration and various types of anaerobic energy production. Hydrogen and electrons are cleaved from substrates by pyridine nucleotide enzymes (PN). The flow of electrons is directed from a system with a lower (more negative potential) to a system with a higher (more positive) potential, from - 0.8 - 0.4 V (substrate potential) to +0.8 V (oxygen potential). [ ...]

The method for assessing the kinetics of consumption of an additional substrate by a microbial population to calculate heterotrophic activity initially does not take into account the possible loss of labeled carbon due to the formation of carbon dioxide during periods of incubation. It has been found that, depending on the type of substrate, 8-60% of the introduced labeled carbon can be lost during respiration during even a 3-hour incubation period.[ ...]

The mechanism of removal from solution and subsequent dissimilation of the substrate is very complex and multi-stage nature of interrelated and sequential biochemical reactions determined by the type of nutrition and respiration of bacteria.[ ...]

Injury to the organs and tissues of the plant increases the intensity of respiration. Perhaps this is due to the destruction of cells, which increases the contact of respiratory substrates and enzymes. Partial injury can cause cells to enter the meristematic growth phase. The intensity of respiration of dividing cells is always higher compared to those that have completed growth.[ ...]

Many simple phenols affect the energetics of the system and the oxidation of substrates during cellular respiration.[ ...]

The relative role of these respiratory pathways may vary depending on the type of plant, age, developmental phase, and also depending on the environmental conditions. The process of respiration of plants is carried out in all your conditions in which life is possible. The plant organism does not have adaptations for temperature regulation, therefore the respiration process is carried out at a temperature of -50 to +50 °C. Plants have no adaptations to maintain an even distribution of oxygen throughout all tissues. It was the need to carry out the process of respiration under various conditions that led to the development in the process of evolution of various pathways of respiratory exchange and to an even greater variety of enzyme systems that carry out individual stages of respiration. It is important to note the interconnection of all metabolic processes in the plant organism. The change in the way of respiratory exchange leads to profound changes in the entire metabolism of plant organisms.[ ...]

Water content. A slight water deficit of growing tissues increases the intensity of respiration. This is due to the fact that water deficiency and even wilting of leaves enhances the breakdown of complex carbohydrates (starch) into simpler ones (sugar). An increase in the sugar content of this main substrate of respiration enhances the process itself. At the same time, with water deficiency, the conjugation of oxidation and phosphorus formation is disrupted. Breathing under these conditions is basically a waste of dry matter. With prolonged wilting, the plant consumes sugar and the intensity of respiration drops. A different pattern is characteristic of organs that are at rest. Increasing the water content in seeds from 12 to 18% already increases the respiration intensity by 4 times. A further increase in the water content to 33% leads to an increase in the intensity of respiration by about 100 times. When a plant or tissue is moved from water to a salt solution, respiration is stimulated - this is the so-called salt respiration.[ ...]

Lack of water also changes such basic physiological processes like photosynthesis and respiration. First of all, during dehydration, the stomata close, which sharply reduces the supply of carbon dioxide to the leaf, and as a result, the intensity of photosynthesis decreases. However, a decrease in water content reduces the intensity of photosynthesis in plants that do not have stomata (MHP, lichen). Apparently, dehydration, by changing the conformation of the enzymes involved in the process of photosynthesis, reduces their activity. This is due to the fact that as a result of the decrease in the process of starch breakdown, the amount of sugars, this main substrate of respiration, increases. At the same time, with a lack of water in the cells, the energy released during respiration does not accumulate in ATP, but is mainly released in the form of heat. Because of this, increased respiration, accompanied by the breakdown of organic substances, can harm the plant organism.[ ...]

Most often molding is caused by fungi from the genera Mi-cor, Aspergillus, Dematium, living on different substrates and very common in nature. The most severely affected by mold are seeds that contain a large amount of water, are damaged, and also stored in conditions of high humidity. The harm from mold lies in the fact that fungi envelop seeds with mycelium, disrupt respiration and other physiological processes that occur in seeds during storage, and often cause their death. Sometimes moldy seeds sprout, but they develop slowly and, as a rule, are strongly affected by various pathogens.[ ...]

Denitrification, being a microbiological process, is only a special form of respiration in the absence of oxygen. A lot of bacteria in a biological treatment plant Wastewater, mainly proteolytic bacteria, can provide a reduction in nitrogen and nitrate in the absence of free oxygen and in the presence of a suitable substrate that serves as a source of hydrogen. Thus, chemically bound oxygen can be used for the metabolic processes of these bacteria. The ability to denitrify is acquired by bacteria in the process of adaptation. The hydrocarbon source must be dosed in the minimum proportion corresponding to the content of nitrates.[ ...]

Since oxidation is part of any aerobic process, this means that the organic substrate can never be converted 100% into biomass organic matter. Of course, if the formation of carbon dioxide is taken into account, there will be no loss of carbon. In the processes of accumulation of reserve substances, the increase can reach 0.95 g COD/g COD(B). Another limiting situation - the entire substrate is spent on maintaining the vital activity of cells (endogenous respiration), resulting in an increase in biomass zero or even negative. For a given amount of substrate, the increase in biomass depends on the duration of the process.[ ...]

The incorporation of (Eyu into extracted mitochondria) leads to a significant increase in the signal induced by the substrate (by 80% on average) and restores its dependence on Fn, but not on ADP. , apparently, with a violation of membrane structures during the extraction of ubiquinone.[ ...]

Dissimilation of carbohydrates can occur in two ways. In pome fruits, sugar is mainly consumed for respiration along the EMP path (Embden - Meyerhof - Parnassus). At the same time, in connection with the processes of phosphorylation, glucose is broken down to pyruvic acid (glycolysis). In addition, there is the possibility of splitting carbohydrates along the pentose cycle. To what extent this cycle is involved in the transformation of respiratory substrates cannot yet be said. At present, it is assumed that at certain stages of the development of an apple or other fruits, one or another path predominates. The EMF pathway, predominant in pome fruits, ends with pyruvic acid, which plays a crucial role in respiration. From this moment on, further transformations of pyruvic acid depend on the environment: in aerobic - with the consumption of oxygen, in anaerobic - when oxygen is not required.[ ...]

According to the nature of dissimilation, aerobic and anaerobic organisms are distinguished. Aerobic (from Greek aer - air) organisms use free oxygen for respiration (oxidation). Aerobes are the majority of living organisms. On the contrary, anaerobes oxidize substrates, for example, sugars in the absence of oxygen, therefore, for them, respiration is fermentation. Anaerobes are many microorganisms, helminths. For example, dinitrifying anaerobic bacteria oxidize organic compounds using nitrite, which is an inorganic oxidizing agent.[ ...]

As already mentioned, many groups of bacteria (for example, facultative anaerobes) are capable of both aerobic and anaerobic respiration, but the end products of these two reactions are different and the amount of energy released during anaerobic respiration is much less. On fig. Figure 2.7 shows the results of an interesting study in which the same bacterial species, Arobacler, was grown under both anaerobic and aerobic conditions using glucose as a carbon source. In the presence of oxygen, almost all glucose was converted into bacterial biomass and CO2; in the absence of oxygen, the decomposition was incomplete, a much smaller part of glucose was converted into carbon-containing substances of the cells, and a series of organic compounds. To oxidize them would require other specialized types bacteria. When the rate of entry of organic detritus into the soil and bottom sediments is high, bacteria, fungi, protozoa, and other organisms create anaerobic conditions by using oxygen faster than it diffuses into the substrate. At the same time, the decomposition organic matter does not stop - it continues, although often at a slower pace, if the environment contains microorganisms with a fairly wide range of anaerobic metabolic types.[ ...]

The DC value also depends on other factors. In some tissues, due to the difficult access of oxygen, along with aerobic respiration, anaerobic respiration occurs, which is not accompanied by oxygen uptake, which leads to an increase in the DC value. The value of the coefficient is also determined by the completeness of the oxidation of the respiratory substrate. If, in addition to end products, less oxidized compounds (organic acids) accumulate in the tissues, then DC[ ...]

Dynamics of carbon dioxide release (С?СО2), oxygen uptake ([ ...]

As soon as water begins to enter the seeds, first of all, respiration increases sharply in them and at the same time various enzymes that were formed during the ripening period are activated. Under their influence, reserve nutrients are hydrolyzed, turning into a mobile, easily digestible form. Fats and starch are converted into organic acids, and sugars, proteins into amino acids. Moving into the embryo from the storage organs, nutrients become a substrate for the synthesis processes that begin in it, primarily new nucleic acids and enzymatic proteins necessary for the start of growth.[ ...]

The metabolic nature of the second stage of consumption is also confirmed by the absence, after the first stage of absorption of the substance, of further accumulation of C14 by the culture when the respiration of bacteria is inhibited by introducing potassium cyanide into the substrate.[ ...]

Excessively developed vegetation impedes the proper operation of ponds, contributes to the deterioration of the hydrochemical and gas regimes, especially at night, when oxygen is consumed by all aquatic organisms for breathing and its deficiency is created. During the decomposition of dying vegetation, toxic decay products (ammonia, hydrogen sulfide, etc.) are released, and its remains are a substrate for the preservation and reproduction of saprophytic and pathogenic fungi, bacteria.[ ...]

For the normal course of protein synthesis in the plant organism of puyashi, the following conditions are: 1) availability of nitrogen; 2) provision with carbohydrates (carbohydrates are necessary both as a material for building the carbon skeleton of amino acids and as a substrate for respiration); 3) high intensity and conjugation of the process of respiration and phosphorylation. At all stages of the transformation of nitrogenous substances (reduction of nitrates, formation of amides, activation of amino acids during protein synthesis, etc.), energy is needed, contained in macroergic phosphorus bonds (ATP); 4) the presence of nucleic acids: DNA is necessary as a substance in which information about the sequence of amino acids in the synthesized protein molecule is encrypted; i-RNA - as an agent that ensures the transfer of information from DNA to ribosomes; t-RNA - cap providing the transfer of amino acids to ribosomes; 5) ribosomes, structural units where protein synthesis occurs; 6) enzyme proteins, protein synthesis catalysts (aminoacyl-t-RNA spptetases); 7) a number of mineral elements (ions Mg2+, Ca2+).[ ...]

In the Volga delta, KV Gorbunov (1955) identified 4 periods in the development of fouling: embryonic, rapid growth, moderate activity, and biomass reduction. The number of species and the biomass of fouling reached a maximum on the 10th day. By this time, the intensity of photosynthesis and respiration decreased, more than half of the biomass of fouling was accounted for by protozoa, rotifers, and bacteria. According to other authors (Cattaneo, 1975), it took about 4 weeks to stabilize the fouling and achieve their similarity with communities on natural substrates.[ ...]

All physiological processes in a plant proceed normally only when it is optimally supplied with water. Water is not only a solvent, but also an active structural component cells. It participates in biological transformations, for example, facilitates the interaction between molecules, serves as a substrate for photosynthesis, participates in respiration and numerous hydrolytic and synthetic processes.[ ...]

Among other classes of vertebrates, fish, especially freshwater, perhaps more often than others, are faced with an unfavorable oxygen regime, in particular with its seasonal and daily fluctuations in water bodies, with an acute shortage in winter. Therefore, according to the nature of energy metabolism, according to the ratio of the specific gravity of glycolysis and respiration, fish occupy, as it were, an intermediate position between facultative anaerobes (invertebrates) and typical aerobes (higher vertebrates). Special studies have shown that fish are characterized by a reduced level of oxidative processes and a reduced activity of the cytochrome system in comparison with warm-blooded animals. According to these authors, the oxidative systems of fish are "more primitive" than those of higher vertebrates. For example, the activity of cytochrome oxidase in certain species of bony fish is high, while the content of cytochrome b is low. In addition, not only cytochrome b serves as a substrate for fish cytochrome oxidase. Consequently, the most important respiratory enzyme, which completes the stages of respiration, is devoid of strict specificity. The system of oxidative phosphorylation in fish functions less efficiently than in other groups of vertebrates.[ ...]

When analyzing the relationship between size and metabolism in plants, it is often difficult to decide what, in fact, is considered an "individual". So, a large tree can be considered as one individual, but when studying the relationship of size with surface area, leaves can be considered “functional individuals” (recall the concept of “leaf area index”). studying different types large marine multicellular algae, we find that species with thin, or narrow, "branches" (i.e., with a high surface area / volume ratio) are characterized by more high level food production per 1 g of biomass, more intense respiration and absorption of radioactive phosphorus from water than species with thick "branches" (E. Odum, Kuentzler, Blunt, 1958). In this case, "functional individuals" are "branches" or even individual cells, and not the whole plant, which can be formed by many "branches" attached to the substrate by a single rhizoid.

The question of the substances used in the process of respiration has long occupied physiologists. Even in the works of I.P. Borodin (1876) showed that the intensity of the respiration process is directly proportional to the content of carbohydrates in plant tissues. This gave reason to assume that it is carbohydrates that are the main substance consumed during respiration (substrate).

In clarifying this issue, the determination of the respiratory coefficient is of great importance. The respiratory coefficient (RC) is the volume or molar ratio of CO2 released during respiration to the CO2 absorbed over the same period of time. With normal oxygen access, the DC value depends on the substrate of respiration. If carbohydrates are used in the breathing process, then the process proceeds according to the equation С6Н1206 + 602 -> 6С02 + 6Н20. In this case, DC is equal to one: 6CO2/602 = 1. However, if more oxidized compounds, such as organic acids, undergo decomposition during respiration, oxygen uptake decreases, DC becomes greater than one. So, if malic acid is used as a breathing substrate, then DC = 1.33. When more reduced compounds, such as fats or proteins, are oxidized during respiration, more oxygen is required and DC becomes less than unity. So, when using fats DC = 0.7. The determination of the respiratory coefficients of different plant tissues shows that under normal conditions it is close to unity. This gives reason to believe that the plant primarily uses carbohydrates as a respiratory material. With a lack of carbohydrates, other substrates can be used. This is especially evident in seedlings that develop from seeds, which contain fats or proteins as a reserve nutrient. In this case, the respiratory coefficient becomes less than one. When used as a respiratory material, fats are broken down into glycerol and fatty acids. Fatty acids can be converted to carbohydrates through the glyoxylate cycle. The use of proteins as a substrate for respiration is preceded by their breakdown into amino acids.

32. Anaerobic respiration plants(glycolysis)

First stage anaerobic decomposition of carbohydrates is the formation of a number of phosphate esters of sugars (hexoses). Glycolysis occurs in the cytoplasm.

Glycolysis is carried out in all living cells of organisms. In the process of glycolysis, a hexose molecule is converted to two molecules of pyruvic acid.

At the first stage, the glucose molecule, under the action of the hexokinase enzyme, takes the phosphoric acid residue from ATP, which is converted into ADP, and as a result, glucopyranose-6-phosphate is formed. The latter, under the action of the enzyme phosphohexoisomerase (oxoisomerase), is converted into fructofuranose-6-phosphate. At a further stage of glycolysis of fructofuranose-6-phosphate, another phosphoric acid residue is attached to it. The source of energy for the formation of this ether is also the ATP molecule. This reaction is catalyzed by phosphohexokinase activated by magnesium ions. As a result, fructofuranose-1,6-diphosphate and a new adenosine diphosphate molecule are formed.

The next step in glycolysis is the oxidation of 3-phosphoglyceraldehyde by specific dehydrogenase and the phosphorylation of glyceric acid using the mineral phosphoric acid. The 1,3-diphosphoglyceric acid formed as a result of this reaction, with the participation of the phosphoferase enzyme, transfers one phosphoric acid residue to the ADP molecule, which is converted into ATP, and 3-phosphoglyceric acid is formed. The latter, under the action of the enzyme phosphoglyceromutase, is converted into 2-phosphoglyceric acid, which, under the influence of the enzyme enolase, is converted into phosphoenolpyruvic acid and finally into pyruvic acid.

The formation of pyruvic acid from phosphoenolpyruvate ends the glycolytic cleavage of hexose by the type of alcoholic fermentation.

Krebs cycle

Second phase of breathing aerobic- localized in mitochondria and requires the presence of oxygen. Pyruvic acid enters the aerobic phase of respiration.

The process can be divided into three main stages:

1) oxidative decarboxylation of pyruvic acid;

2) tricarboxylic acid cycle (Krebs cycle);

3) the final stage of oxidation - the electron transport chain (ETC) requires the obligatory presence of 0 2 .

The first two stages occur in the mitochondrial matrix; the electron transport chain is localized on the inner mitochondrial membrane.

First stage- oxidative decarboxylation of pyruvic acid. This process consists of a series of reactions and is catalyzed by a complex multienzymatic system, pyruvate decarboxylase. Pyruvate decarboxylase includes three enzymes and five coenzymes (thiamine pyrophosphate, lipoic acid, coenzyme A - KoA-SH, FAD and NAD). As a result of this process, an active acetate is formed - acetyl coenzyme A (acetyl-CoA), reduced by NAD (NADH + H +), and carbon dioxide is released (the first molecule). Reduced NAD enters the electron transport chain, and acetyl-CoA enters the tricarboxylic acid cycle.

Second stage- tricarboxylic acid cycle (Krebs cycle). In 1935, the Hungarian scientist A. Szent-Gyorgyi found that the addition of small amounts of organic acids (fumaric, malic or succinic) enhances the absorption of oxygen by crushed tissues. Continuing these studies, G. Krebs came to the conclusion that the main way of carbohydrate oxidation is cyclic reactions, in which a number of organic acids are gradually converted. These transformations were called the tricarboxylic acid cycle or the Krebs cycle. The researcher himself was awarded the Nobel Prize in 1953 for these works.

The essence of the cycle is the decarboxylation of pyruvic acid.

Active acetate, or acetyl-CoA, enters the cycle. The essence of the reactions included in the cycle is that acetyl-CoA is condensed with oxaloacetic acid (OAA). Further, the transformation goes through a series of di- and tricarboxylic organic acids. As a result, the PIEC regenerates in its original form. During the cycle, three H 2 0 molecules are added, two CO 2 molecules and four hydrogen pairs are released, which restore the corresponding coenzymes (FAD and NAD).

Acetyl-CoA, condensing with PHA, gives citric acid, while CoA is released in its original form. This process is catalyzed by the enzyme citrate synthase. Citric acid is converted to isocitric acid. The next step is the oxidation of isocitric acid, the reaction is catalyzed by the enzyme isocitrate dehydrogenase. In this case, protons and electrons are transferred to NAD (NADH + H+ is formed). This reaction requires magnesium or manganese ions. At the same time, the process of decarboxylation takes place. Due to one of the carbon atoms that entered the Krebs cycle, the first CO 2 molecule is released. The resulting a-ketoglutaric acid undergoes oxidative decarboxylation. This process is also catalyzed by the multienzyme complex ketoglutarate dehydrogenase. As a result, the second CO 2 molecule is released due to the second carbon atom entering the cycle. At the same time, another NAD molecule is reduced to NADH and succinyl-CoA is formed.

In the next step, succinyl-CoA is cleaved into succinic acid (succinate) and HS-CoA. The energy released in this case is stored in the macroergic phosphate bond of ATP. The resulting succinic acid is oxidized to fumaric acid. The reaction is catalyzed by the enzyme succinate dehydrogenase. At the same time, a third pair of hydrogens is released, forming FAD-H 2 .

At the next stage, fumaric acid, by attaching a water molecule, is converted into malic acid using the enzyme fumarate dehydrogenase. At the last stage of the cycle, malic acid is oxidized to PAA.

With each stage of the cycle, one molecule of pyruvic acid disappears, and 3 molecules of CO 2 and 5 pairs of hydrogen atoms of electrons are split off from different components of the cycle.

A variation of the Krebs cycle is the glyoxylate cycle. Two-carbon compounds, such as acetate, act as a source of carbohydrates, and glyoxylic acid is involved. R-tions of the glyoxylate cycle underlie the conversion of stored fat into carbohydrates. The enzymes of this cycle are located in the cell bodies - glyoxisomes.

In the glyoxylate cycle, in contrast to the Krebs cycle, isocitric acid decomposes into succinic and glyoxylic acids. . Glyoxylate, with the participation of malate synthase, interacts with the second molecule of acetyl-Co A, as a result of which malic acid is synthesized, which is oxidized to AAA.

In contrast to the Krebs cycle, in the glyoxylate cycle, not one, but two molecules of acetyl-CoA are involved in each turn, and this activated acetyl is used not for oxidation, but for the synthesis of succinic acid. Succinic acid leaves glyoxisomes, turns into PAA and participates in gluconeogenesis (reversed glycolysis) and other biosynthesis processes. The glyoxylate cycle allows the utilization of reserve fats, during the breakdown of which molecules of acetyl-CoA are formed. In addition, for every two molecules of acetyl-CoA in the glyoxylate cycle.

The physiological meaning of the glyoxylate cycle consists in an additional pathway for the decomposition of fats and the formation of a number of various intermediate compounds that play an important role in biochemical reactions.

Energetics of the Krebs cycle

Krebs cycle. plays an extremely important role in the metabolism of the plant organism. It serves as the final stage in the oxidation of not only carbohydrates, but also proteins, fats and other compounds. During the reactions of the cycle, the main amount of energy contained in the oxidized substrate is released, and most of this energy is not lost to the body, but is utilized during the formation of high-energy final phosphate bonds of ATP.

In the aerobic phase of respiration, during the oxidation of pyruvic acid, 4 molecules of NADH + H + are formed. Their oxidation in the respiratory chain leads to the formation of 12 ATP. In addition, one molecule of flavin dehydrogenase (FADH2) is reduced in the Krebs cycle. Oxidation of this R compound in the respiratory chain results in the formation of 2 ATP, since phosphorylation alone does not occur. When a molecule of a-ketoglutaric acid is oxidized to succinic acid, energy is directly accumulated in one ATP molecule (substrate phosphorylation). Thus, the oxidation of one molecule of pyruvic acid is accompanied by the formation of 3CO2 and 15 ATP molecules. However, when a glucose molecule breaks down, two molecules of pyruvic acid are obtained.

The question of the substances used in the process of respiration has long occupied physiologists. Even in the works of I.P. Borodin (1876) showed that the intensity of the respiration process is directly proportional to the content of carbohydrates in plant tissues. This gave reason to assume that it is carbohydrates that are the main substance consumed during respiration (substrate). In clarifying this issue, the determination of the respiratory coefficient is of great importance. Respiratory coefficient(DC) is the volume or molar ratio of CO 2 released during respiration to that absorbed over the same period of time About 2 . With normal access to oxygen, the DC value depends on the substrate of respiration. If carbohydrates are used in the breathing process, then the process proceeds according to the equation C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O. In this case, DC is equal to one: 6CO 2 / 6O 2 \u003d 1. However, if decomposition during breathing more oxidized compounds, such as organic acids, are exposed, oxygen uptake decreases, DC becomes greater than one. So, if malic acid is used as a breathing substrate, then DC = 1.33. When more reduced compounds, such as fats or proteins, are oxidized during respiration, more oxygen is required and DC becomes less than unity. So, when using fats DC = 0.7. The determination of the respiratory coefficients of different plant tissues shows that under normal conditions it is close to unity. This gives reason to believe that the plant primarily uses carbohydrates as a respiratory material. With a lack of carbohydrates, other substrates can be used. This is especially evident in seedlings that develop from seeds, which contain fats or proteins as a reserve nutrient. In this case, the respiratory coefficient becomes less than one. When used as a respiratory material, fats are broken down into glycerol and fatty acids. Fatty acids can be converted to carbohydrates through the glyoxylate cycle. The use of proteins as a substrate for respiration is preceded by their breakdown into amino acids.

Exist two main systems and two main ways transformation of the respiratory substrate, or oxidation of carbohydrates: 1) glycolysis + Krebs cycle (glycolytic); 2) pentose phosphate (Apotomtesque). The relative role of these respiratory pathways may vary depending on the type of plants, age, developmental phase, and also depending on environmental factors. The process of respiration of plants is carried out in all external conditions under which life is possible. The plant organism does not have adaptations for temperature regulation, therefore

The breathing process is carried out at a temperature of -50 to +50°C. Plants have no adaptations to maintain an even distribution of oxygen throughout all tissues. It was the need to carry out the process of respiration under various conditions that led to the development in the process of evolution of various pathways of respiratory exchange and to an even greater variety of enzyme systems that carry out individual stages of respiration. It is important to note the relationship of all metabolic processes in the body. Changing the way of respiratory exchange leads to profound changes in the entire metabolism of plants.