General and specific metabolic pathways. Specific and general pathways of catabolism. Schizophrenia, catecholamines and internal antipsychotics

There are three stages in catabolism:

one). Polymers are converted into monomers (proteins into amino acids, carbohydrates into monosaccharides, lipids into glycerol and fatty acid). The chemical energy is dissipated in the form of heat.

2). The monomers are converted into common products, the vast majority into acetyl-CoA. Chemical energy is partially dissipated in the form of heat, partially accumulated in the form of reduced coenzyme forms (NADH, FADH 2), and partially stored in macroergic bonds of ATP (substrate phosphorylation).

1st and 2nd stages of catabolism refer to specific pathways that are unique to the metabolism of proteins, lipids, and carbohydrates.

3). The final stage of catabolism is reduced to the oxidation of acetyl-CoA to CO 2 and H 2 O in the reactions of the tricarboxylic acid cycle (Krebs cycle) - general path of catabolism. Oxidative reactions of the general path of catabolism are associated with a chain of tissue respiration. At the same time, energy (40-45%) is stored in the form of ATP (oxidative phosphorylation).

As a result of specific and general pathways of catabolism, biopolymers (proteins, carbohydrates, lipids) break down to CO 2 , H 2 O and NH 3 , which are the main end products of catabolism.

Metabolites in normal and pathological conditions

Hundreds of metabolites are formed every second in a living cell. However, their concentrations are maintained at a certain level, which is a specific biochemical constant or reference value. In diseases, there is a change in the concentration of metabolites, which is the basis of biochemical laboratory diagnostics. Normal metabolites include glucose, urea, cholesterol, total serum protein, and a number of others. The output of the concentration of these substances beyond the limits of physiological norms (increase or decrease) indicates a violation of their metabolism in the body. Moreover, a number of substances in the body of a healthy person are found only in certain biological fluids, which is due to the specifics of their metabolism. For example, serum proteins do not normally pass through the kidney filter and are therefore not found in the urine. But with inflammation of the kidneys (glomerulonephritis), proteins (primarily albumins) penetrate the glomerular capsule, appear in the urine - proteinuria and are interpreted as pathological components of urine.

Pathological metabolites are myeloma proteins (Bence-Jones proteins), paraproteins in Waldenström's macroglobulinemia, the accumulation of abnormal glycogen in glycogenosis, various fractions of complex lipids in sphingolipidoses, etc. They are found only in diseases and are not characteristic of a healthy body.

Levels of study of metabolism

Levels of study of metabolism:

Whole organism.

Isolated organs (perfused).

Sections of fabrics.

Cell cultures.

tissue homogenates.

Isolated cell organelles.

Molecular level (purified enzymes, receptors, etc.).

Quite often, radioactive isotopes (3 H, 32 P, 14 C, 35 S, 18 O) are used to study metabolism, which mark substances introduced into the body. You can then follow the cellular localization of these substances, determine the half-life and their metabolic pathways.

Rice. 8.1. Diagram of specific and general pathways of catabolism

In contrast to the diversity of the macrocosm (the world of large creatures visible to the naked eye), the microbial world is characterized by relative monotony. Currently over 3000 various kinds bacteria, but their appearance is divided into 3 main forms:

Spherical or elliptical (cocci) ranging in size from 1 to 2 microns (Fig. 1.3). Cocci are among the simplest form of bacteria; they can combine with each other, forming diplococci (two each), tetracocci (four each) and streptococci (chains); - rod-shaped or cylindrical in size from 1 to 5 micro (Fig. 1.4). They are also able to connect with each other in pairs and in a chain and give a wide variety of forms of bacteria (diplobacteria, diplobacilli, streptobacilli, streptobacteria); - Convoluted or spirillos ranging in size from 1 to 30 microns.

Microorganisms-destructors. The leading role in the transformation and mineralization of organic xenobiotics belongs to chemoorganotrophic (heterotrophic) microorganisms, especially bacteria synthesizing various enzyme systems.

Of the bacteria that break down organic xenobiotics, Pseudomonas occupy the first place in terms of frequency of occurrence, the number of species (about 30), and the spectrum of degradable compounds.

The biodegrading activity of a microbial community depends on its composition, growth rate, and exchange of nutrients and genetic material between species. Accumulated metabolites can be toxic to one component of the community and can be absorbed by other microorganisms, which together accelerates the decomposition process (detoxification phenomenon).

Taking into account the methods of obtaining biological objects - destructors of xenobiotics, there are two options for biopurification and bioremediation. The first option is for areas with old pollution, where wild, native microflora almost always lives, capable of transforming them. These contaminants can be removed in situ(in place) without the introduction of biological products. At the same time, biodegradation is limited by environmental factors and pollution properties, such as the oxygen content in the environment, the solubility of the pollutant, etc. The second option is to first obtain a biologically active strain, accumulate viable cells, which are introduced as a biological product into the contaminated environment. This option is advisable to use in the northern regions and when processing places with non-old pollution;

The ability of microorganisms to destroy a xenobiotic or other pollutant depends on the presence in cells of genes that determine the synthesis of enzymes involved in the degradation of the compound. The construction of recombinant xenobiotic destructor strains consists in combining several genes or their blocks responsible for the primary metabolism of compounds. The advantage of such a combination is that genetically modified microorganisms (GMMOs) can synthesize various enzyme systems, which makes it possible to effectively and quickly destroy a wide range of chemical contaminants.

Biological wastewater treatment. Schematic diagrams treatment facilities. Basic principles of operation, methods and facilities for aerobic and anaerobic biological wastewater treatment and industrial waste processing.

Classification of biological cleaning methods. Biological treatment methods are used to treat domestic and industrial wastewater (Fig. 2.1) from many dissolved organic and some inorganic substances (hydrogen sulfide, sulfides, ammonia, nitrates, etc.). The cleaning process is based on the ability of microorganisms to use these substances for nutrition. Contacting with organic substances, microorganisms partially destroy them, turning them into water, carbohydrate dioxide, nitrite, sulfation, etc. Organic substances are a source of carbon for microorganisms. The destruction of organic matter by microorganisms is called biochemical oxidation.

Anaerobic microbiological processes are carried out with the mineralization of both dissolved organic substances and the solid phase of wastewater. Anaerobic processes proceed at a slow pace, go without access to oxygen, and are used mainly for the fermentation of sediments. The aerobic cleaning method is based on the use of aerobic groups of microorganisms, the vital activity of which requires a constant supply of oxygen and a temperature of 20-40°C.

The availability of a substance for biological oxidation can be assessed by the value of a biochemical index, which is understood as the ratio of total BOD (BOD total) and COD. The biochemical indicator is a parameter necessary for the calculation and operation of industrial biological facilities for wastewater treatment. When the value of the biochemical index is equal to or more than 0.5, the substances are amenable to biochemical oxidation. The value of the biochemical index varies widely for different groups of wastewater. Industrial wastewater has a low rate (0.05 - 0.3), domestic wastewater - over 0.5.

Facilities for biological wastewater treatment. The main facilities for biochemical treatment are aerotanks and secondary settling tanks.

The aerotank is a device with constantly flowing waste water, in the entire thickness of which aerobic microorganisms develop, consuming the substrate, i.e. "contamination" of this waste water. Biological wastewater treatment in aerotanks occurs as a result of the vital activity of activated sludge microorganisms. Waste water is continuously mixed and aerated until it is saturated with oxygen in the air. Activated sludge is a suspension of microorganisms capable of flocculation.

There is also a classification of aerotanks according to the "load" on activated sludge: high-loaded (aerotanks for incomplete cleaning), ordinary and low-loaded (aerotanks with extended aeration). The aeration system is of great importance in the design of aeration tanks. Aeration systems are designed to supply and distribute oxygen or air in the aeration tank, as well as to maintain activated sludge in suspension.

Aerotanks-mixers(full mixing aerotanks, Fig. 2, handout) are characterized by a uniform supply of initial water and activated sludge along the length of the structure and a uniform removal of the sludge mixture. The complete mixing of wastewater with the sludge mixture in them ensures the alignment of sludge concentrations and the rates of the biochemical oxidation process, therefore aeration tanks-mixers are more suitable for the treatment of concentrated industrial wastewater (full BOD up to 1000 mg/l) with sharp fluctuations in their flow rate, composition and amount of pollution .

Aerotanks-displacers. Unlike aerotanks of other types (aerotanks-mixers and aerotanks of an intermediate type), aerotanks-displacers (Fig. 2. , handout) are structures in which the treated wastewater gradually moves from the inlet to the place of its release. In this case, there is practically no active mixing of the incoming wastewater with the previously received. The processes occurring in these structures are characterized by a variable reaction rate, since the concentration of organic pollutants decreases in the direction of water movement. Aerotanks-displacers are very sensitive to changes in the concentration of organic substances in the incoming water, especially to volleys of toxic substances with wastewater, therefore, such facilities are recommended for the treatment of urban and similar in composition to domestic industrial wastewater.

Aerotanks with dispersed inlet(Fig. 2, handout) waste water occupy an intermediate position between mixers and displacers; they are used to treat mixtures of industrial and municipal wastewater.

Aerotanks can be combined with separate secondary settling tanks or combined into a block with a rectangular shape of both structures in the plan. The most compact combined structures are aerotanks-settlers. Abroad, this type of structure, round in plan, with mechanical aerators, was called an aeroaccelerator. The combination of the aerotank with the sump makes it possible to increase the recirculation of the sludge mixture without the use of special pumping stations, improve the oxygen regime in the sump and increase the sludge dose to 3-5 g/l, thus increasing the oxidative power of the facility.

Variety aeration tank- the aero accelerator is a round structure in terms of plan. Clarified wastewater enters the lower part of the aeration zone, where air is supplied pneumatically or pneumomechanically, which ensures the process of biochemical oxidation, and also creates a circulating movement of the liquid in this zone and suction of the sludge mixture from the circulating zone of the sump. From the aeration zone, the sludge mixture enters the air separator through flooded adjustable overflow windows and then to the circulating zone of the settling tank. A significant part of the sludge mixture returns to the aeration zone through the slot, and the discharged treated wastewater enters the settling zone through a layer of suspended sediment.

Secondary clarifiers are an integral part of biological treatment facilities, are located in the technological scheme directly after biooxidizers and serve to separate activated sludge from biologically treated water leaving the aerotanks, or to retain the biological film coming with water from biofilters. The efficiency of the secondary settling tanks determines the final effect of water purification from suspended solids. For technological schemes of biological wastewater treatment in aerotanks, secondary settling tanks to some extent also determine the volume of aeration facilities, which depends on the concentration of return sludge and the degree of its recirculation, the ability of settling tanks to effectively separate highly concentrated sludge mixtures.

The sludge mixture coming from the aerotanks to the secondary settling tanks is a heterogeneous (multiphase) system in which biologically treated wastewater serves as a dispersion medium, and the main component of the dispersed phase is activated sludge pops formed in the form of a complex three-level cellular structure surrounded by an exocellular substance of a biopolymer composition.

Anaerobic treatment is used to remove contaminants from wastewater, as the first stage of wastewater treatment with a high concentration of organic pollutants (BOD n> 4-5 g/l), as well as for the treatment of activated sludge, other sludge and solid waste. Many solid wastes contain cellulose, which is more easily decomposed into biogas by anaerobic decomposition than by aerobic oxidation.

During methane generation (methanogenesis) - an anaerobic process with the formation of methane - organic pollution is converted into biogas, containing mainly CH 4 and CO 2. It can be used as fuel. The amount of biogas released is sufficient not only to compensate for the energy costs for anaerobic decomposition, but also for use by third-party consumers - in boiler houses or heaters for generating steam and hot water, in stationary gas generators for generating electricity with heat recovery, in technological processes of thermal drying and burning of sludge and others

Biocenoses and biochemical processes during anaerobic treatment. Formation of cenoses. Anaerobic biocenoses in wastewater treatment can be represented by floccules, biofilms and silt granules. They develop in ecosystems with dominance of anoxygenic and anaerobic conditions, in which the processes of fermentation, anoxygenic oxidation (anaerobic respiration), and methane formation take place.

Anoxygenic oxidation of organic substrates includes the processes of denitrification and sulfate reduction occurring in the presence of NO 3 , - N0 2 - , S0 4 2- ions and, as a rule, in the absence of oxygen. These processes are used to remove nitrogen and sulfur compounds from wastewater.

The main process that occurs under anaerobic conditions and is used to decompose and remove organic contaminants and waste is methanogenesis. In the process of methane generation (often referred to as "methane fermentation"), organic substrates and contaminants are decomposed, wastewater is disinfected and detoxified. In nature, this process takes place in various environments with anaerobic conditions, in the rumen of ruminants, in termite mounds.

Methane generation is a complex, multi-stage process in which the initial organic substances are successively converted into simpler ones with the transition of a significant part of carbon into methane and carbon dioxide and into the silt liquid. Methane decomposition includes three stages of anaerobic fermentation (Fig. 5.1): hydrolysis, acidic (acidogenic), acetogenic and the fourth, methanogenic stage (gas formation stage).

Hydrolytic microorganisms with cellulolytic, proteolytic, amylolytic, lipolytic, and ammonifying activities take part in the first stage of fermentation. The nitrates and sulfates contained in the medium are reduced by denitrifying bacteria and sulfate reducers. As a result of enzymatic hydrolysis, cellulose and hemicelluloses, proteins, fats and other components are hydrolyzed with the formation of fatty acids, glycerol, peptides, amino acids, mono- and disaccharides and, in a small amount, acetic acid, methanol, ammonia, hydrogen. Bacteria pp. participate in hydrolysis. Clostridium, Bacillus, as well as Bacteroides, Butyrivibrio, Cellobacterium, Eubacterium, Bifidobacterium, Lactobacillus, Selenomonas. At the acidogenic stage, various fermentation saws occur: alcohol, butyric, acetone-butyl, propionic and others, during which acidogen bacteria ferment the resulting hydrolysis products, such as glucose, to organic acids:

By consuming mono- and oligosaccharides, amino acids and other intermediate hydrolysis products, these bacteria thereby prevent the hydrolysis products from inhibiting the hydrolytic enzymes involved in the first phase of fermentation.

As a result of splitting in the first two stages, 70-80% of the resulting organic products are higher fatty acids, up to 20% - acetate and 3-5% - hydrogen. Other products include isobutyric, phenylacetic, benzoic, indolylbenzoic acids, NH 4 + , H, S, butanol, propanol, CO 2, etc.

At the acetogenic stage of fermentation, heteroacetogenic bacteria (acetogens) pp. Clostridium, Syntrophus and others convert organic acids, such as propionic and butyric, other products of acidogenesis into acetic acid:

The main role in methane decomposition is played by the final stage, performed by strict anaerobes - methane-forming bacteria. They are more sensitive to environmental conditions. The generation time of methanogen cells is several days. Their activity is maximum at medium pH from 6.8 to 7.5. At lower and higher pH values, the development of methanogens slows down or stops altogether.

The reaction product of the methanogenic stage is CH 4 . Its formation is possible in two ways. Methanogenic lithotrophic bacteria (pp. Methanococcus, Methanobacterium, Methanospirillum, Methanomicrobium, Methanogenium, Methanothermus, Methanobrevibacter) consume H 2 and CO 2 as a substrate, as well as CO and formate:

C0 2 + 4H 2 → CH 4 + 2H 2 0

4НСООН → CH 4 + ЗС0 2 + 2Н,0

4CO + 2H 2 0 → CH 4 + ZC0 2

Acetotrophic microorganisms (pp. Methanosarcina, Melhanosaeta, Methanoplanus) use acetate, methanol, methylamine:

CH 3 COOH → CH 4 + CO 2

4CH 3 OH → ZSN 4 + CO 2 + 2H 2 0

4CH 3 NH 2 + 2H 2 0 → CH 4 + 4NH 3 + CO

Due to the destruction of organic acids, the pH of the medium rises, the reaction of the medium becomes alkaline, therefore the methanogenic stage is sometimes called "alkaline fermentation".

During the decomposition of acetic acid, 70-75% of methane is formed, and the remaining 25-30% - as a result of synthesis from carbon dioxide and hydrogen and other reactions. The ratio of end products in the process of methane fermentation depends on the composition of the medium, the fermentation conditions and the microflora present.

A great stimulus to the development of many of modern methods anaerobic purification served as a discovery in the mid-1970s. the ability of microorganisms that are part of the methanogenic community to form aggregates - granules (pellets) during growth in an anaerobic reactor under conditions of an upward flow (Fig. 5.2 handout).

Methanogenic bacteria Methanosaeta concilii (Methanothrix soehngenii) and Methanosarcina spp. play a special role in the formation and functioning of granules. bacteria p. Methanosaeta form brush-like and tangle-like structures (Fig. 5.3), within which microcolonies of Methanosarcina bacteria are grouped (Fig. 5.4). Due to this, aggregates are formed in the form of dense, easily settling granules 1–5 mm in size.

Traditional structures include septic tanks, clarifiers-decomposers, contact reactors, anaerobic lagoons, digesters, anaerobic biofilters with an upward flow of liquid (see handout, Fig. 3.5).

A septic tank (septic tank) is a device consisting of two parts: a settling and a septic tank (Fig. 6.1). In the first part, water clarification occurs due to its movement at a low speed, and in the second part, located under the first, the sediment rots when stored for 6-12 months. The settling and septic parts of the septic tank are not separated from each other. The duration of water in the septic tank is 3-4 days. Septic tanks are used if the amount of wastewater does not exceed 25 m 3 / day.

Septic tanks are often used for digestion of activated sludge from secondary clarifiers, sediments from primary clarifiers and foam in order to accumulate sediment, reduce its volume, bad smell and the amount of pathogenic microflora. Septic tanks are the most common treatment facilities for individual households, since they can work autonomously and do not need electricity.

Clarifiers-decomposers, which can be considered as a type of septic tank, are used at wastewater treatment plants with a throughput of up to 30,000 m 5 /day. On fig. .2 shows the design of the clarifier - decomposer, made in the form of a combined structure, consisting of a clarifier located concentrically inside the decomposer.

The method of anaerobic treatment in a contact reactor was one of the first to be widely used in industry since the early 1930s, in particular, for the treatment of wastewater from sugar, alcohol and yeast industries. Compared to a septic tank, a contact reactor is much more productive, since it provides for mixing the medium with anaerobic sludge and maintains a higher concentration of sludge by returning part of it from the secondary settling tank (see handout for lecture 3, Fig. 3.5), i.e. similarly how it is implemented in the aerotank with a secondary clarifier. To increase the separation efficiency, the sludge liquid before the secondary settling tank can be additionally subjected to degassing (in a separate container) or cooling. During degassing, the gas is removed mechanically (hydraulicly) or by vacuum. Cooling slows down the processes of methane formation and, as a result, the formation of new bubbles, which improves the sedimentation properties of anaerobic sludge.

The traditional and most common apparatus for anaerobic digestion are digesters. They are used for the digestion of wastewater with a high concentration of pollution and the decomposition of organic waste, in particular, activated sludge from sewage treatment plants.

Methane tanks operate with heating, usually in a batch loading mode of waste or wastewater, with a constant selection of biogas and unloading of solid sludge as the process is completed. They are made of steel, concrete, plastics, bricks; they differ in the shape of the tank, the number of digestion chambers, the method of loading and unloading the substrate, the methods of heating and mixing.

Large volume digesters are made in the form of vertical cylindrical or ellipsoidal tanks with forced mixing of the fermented mass; they are designed for excess gas pressure up to 5 kPa. Small biogas plants can be cylindrical horizontal or vertical bioreactors with mechanical agitation, partially or completely buried in the ground to reduce heat loss. The design of bioreactors must ensure the possibility of complete emptying of the tank, so the bottom is often made beveled, hemispherical or cone-shaped.

Methane tanks with a fixed non-flooded ceiling have a disadvantage inherent in structures with rigid ceilings - the variability of pressure inside the reactor. When the sludge is discharged, a vacuum may form inside the digester, and pressure may increase during loading. This leads to the destruction of structures, the formation of cracks.

Advantages of a digester with a floating ceiling: 1) explosion safety, since, regardless of the filling of the digester, a positive gas pressure is maintained in it, which excludes the possible ingress of air into the structure; 2) according to the position of the floating floor, it is possible to carry out the dosage of loading and unloading; 3) the fight against the formation of a crust is facilitated.

The role of mixing and temperature control in metatanks. All types of metatanks can operate in mesophilic (20-45 °С, usually 30-35 °С) and thermophilic (50-60 °С) temperature regimes. The mode of fermentation is chosen taking into account the methods of subsequent processing and disposal of sediments, as well as sanitary requirements. The mesophilic mode is used more often because it is less energy-intensive and more economical, allows the existence of a larger number of microbial species and is therefore more stable, less sensitive to changes in environmental conditions; Precipitates in this mode after processing are dehydrated better than in the thermophilic process. However, under the thermophilic regime, the rate of decomposition of organic compounds is higher (about 2 times) and the degree of their decomposition is higher, almost complete dehelminthization of precipitation is achieved, which is important if precipitation is used as a reclamator or fertilizer for the soil. The duration of fermentation in the mesophilic mode is 20-30 days, in the thermophilic mode - about 10 days. The calorific value of gas in thermophilic fermentation is 5% lower than in mesophilic.

For a more complete methane generation process, thorough mixing of the contents of the digester is necessary to ensure uniform distribution of the contents of the reactor, the necessary conditions mass and heat transfer, minimize sticking, formation of foam and crust, formation of bottom sediment, remove gases. For mixing in the digester, mechanical agitators, circulation pumps, hydraulic elevators, or a combination of these systems are used.

Optimum concentration of suspended solids in the digester, at which a high intensity of methane formation is observed, is in the range of 2-10%. At a concentration of solid particles above 10-12%, the mixing of the medium is difficult, and this leads to a decrease in gas evolution. In such cases, special designs of bioreactors are used to provide the required level of mixing.

Methane formation proceeds at a maximum rate at pH from 6 to 8. When the pH drops below 5.5 (in the case of "souring" of the digester), the activity of methanogenic bacteria ceases. As a rule, the pH is not adjusted due to the high buffering capacity of the medium. But when the environment is acidified, the best neutralizing agent is a NaHC0 3 solution.

The process of methanogenesis slows down in the presence of various detergents (at their concentration of about 15 mg/l), antibiotics and other substances. Of the anionic surfactants, alkyl sulfates, chlorine sulfanol are relatively completely decomposed and weakly inhibit the fermentation process; are difficult to decompose and strongly inhibit the fermentation of sulfanols.

Anaerobic reactors are resistant to long interruptions in the supply of waste water, changes in the chemical composition of incoming effluents, which makes it possible to effectively use them to treat seasonal production effluents, as well as in low load modes. In the case of a decrease in methanogenic activity, to restore it, it is possible to reduce the feed rate of the substrate, alkalinize the medium with chemicals, dilute the effluent with water, and remove toxic compounds by pre-treatment of the effluent.

Bacterial leaching chemical elements from ores, concentrates and rocks, enrichment of ores, biosorption of metals from solutions. Removal of sulfur from oil and coal. Enhanced oil recovery. Removal of methane from coal seams. Suppression of biocorrosion of oil products.

Studies on the bacterial oxidation of iron and leaching of metals began after the isolation in the 1950s from acidic drainage waters of a coal mine of microorganisms capable of taking part in the oxidation of ferrous iron to ferric iron - bacteria Acidithiobaccilus ferrooxidans (formerly called Thiobaccilus ferrooxidans). Bacteria involved in metal leaching are chemoautotrophic by type of nutrition, catalyzing chemical redox reactions to obtain energy and assimilating carbon dioxide for constructive cell metabolism, i.e. feeding autonomously, without the use of organic matter.

Heap bioleaching of sulfide ores.

In recent years, tank bacterial leaching of concentrates or ores has begun to be used to prepare refractory raw materials for cyanidation. There are already more than a dozen industrial enterprises operating in the world that practice this technology, but the capital costs for this technology are very high, so it is not justified for small and medium-sized deposits.

The use of strictly acidophilic bacteria suggests that the pH value of the pulp or solution is 2 or lower. If A. ferrooxidans bacteria are used for leaching, then the process of biological oxidation of minerals can go in two ways: these bacteria not only oxidize sulfur compounds, but are also capable of oxidizing ferrous forms of iron to oxide forms to obtain energy. The processing time depends on the composition of the sulfide ore, the shape and distribution of the metal in the ore, and the amount of sulfur available to microorganisms. There are also a number of more specific problems, such as the toxicity of high concentrations of mined heavy valuable metals to certain species or strains of leaching microorganisms.

Thus, one of the approaches to improving and developing the technology and methods of bioleaching is the selection of bacteria and archaea that are resistant to metal toxicity. Other criteria for selecting crops are: ease of working with them under industrial conditions, activity in the oxidation of mineral compounds, relation to pH, temperature, aeration regime, and the ability to stimulate their activity by introducing additional substances.

Currently, a number of genera (groups subdivided by properties and systematic position) of bacteria and archaea (two superkingdoms of microorganisms) are known, the representatives of which are capable of leaching metals by oxidizing sulfides: Acidothiobacillus, Halothiobacillus, Thiobacillus, Leptospirillum, Acidiphilium, Sulfobacillus, Ferroplasma, Sulfolobus , Metallosphaera and Acidianus. Thus, the development of bioleaching technologies can be based both on making changes to the organization of the process (optimization of aeration, temperature conditions, pretreatment of mineral raw materials, etc.), and on the selection of new microbial cultures - with higher activity or easier biomass growth, or with wider range of pH, temperature, etc. Traditional leaching with acidic solutions has led to the fact that the search for new cultures of microorganisms is focused specifically on acidophilic and superacidophilic organisms.

Introduction to Metabolism (Biochemistry)

Metabolism or metabolism is a set of chemical reactions in the body that provide it with the substances and energy necessary for life. The process of metabolism, accompanied by the formation of simpler compounds from complex ones, is referred to as catabolism. The process that goes in the opposite direction and ultimately leads to the formation of a complex product from relatively simpler ones is anabolism. Anabolic processes are accompanied by energy consumption, catabolic - release.

Anabolism and catabolism are not simple reaction reversals. Anabolic pathways must be different from the catabolism pathways of at least one of the enzymatic reactions in order to be regulated independently, and by controlling the activity of these enzymes, the overall rate of decay and synthesis of substances is regulated. Enzymes that determine the speed of the entire process as a whole are called key.

Moreover, the path along which the catabolism of a particular molecule proceeds may be unsuitable for its synthesis for energy reasons. For example, the breakdown of glucose to pyruvate in the liver is a process consisting of 11 successive stages catalyzed by specific enzymes. It would seem that the synthesis of glucose from pyruvate should be a simple reversal of all these enzymatic steps of its breakdown. At first glance, this way seems both the most natural and the most economical. However, in reality, the biosynthesis of glucose (gluconeogenesis) in the liver proceeds differently. It includes only 8 out of 11 enzymatic steps involved in its breakdown, and the 3 missing steps are replaced in it by a completely different set of enzymatic reactions, characteristic only of this biosynthetic pathway. In addition, the reactions of catabolism and anabolism are often separated by membranes and occur in different cell compartments.

Table 8.1. Compartmentalization of some metabolic pathways in the hepatocyte

Compartment	metabolic pathways
Cytosol	Glycolysis, many reactions of gluconeogenesis, amino acid activation, fatty acid synthesis
plasma membrane	Energy dependent transport systems
	DNA replication, synthesis of various types of RNA
Ribosomes	protein synthesis
Lysosomes	Isolation of hydrolytic enzymes
Golgi complex	Formation of the plasma membrane and secretory vesicles
Microsomes	Localization of catalase and amino acid oxidases
Endoplasmic reticulum	Lipid synthesis
Mitochondria	Tricarboxylic acid cycle, tissue respiration chain, fatty acid oxidation, oxidative phosphorylation

Metabolism performs 4 functions:

1. supplying the body with chemical energy obtained from the breakdown of energy-rich food substances;

2. the transformation of nutrients into building blocks that are used in the cell for the biosynthesis of macromolecules;

3. assembly of macromolecular (biopolymers) and supramolecular structures of a living organism, plastic and energy maintenance of its structure;

4. synthesis and destruction of those biomolecules that are necessary for the performance of specific functions of the cell and organism.

A metabolic pathway is a sequence of chemical transformations of a particular substance in the body. The intermediate products formed during the transformation process are called metabolites, and the last compound of the metabolic pathway is the final product. An example of a metabolic pathway is glycolysis, the synthesis of cholesterol.

A metabolic cycle is such a metabolic pathway, one of the end products of which is identical to one of the compounds involved in this process. The most important metabolic cycles in the human body are the tricarboxylic acid cycle (Krebs cycle) and the ornithine urea cycle.

Almost all metabolic reactions are ultimately interconnected, since the product of one enzymatic reaction serves as a substrate for another, which in this process plays the role of the next step. Thus, metabolism can be represented as an extremely complex network of enzymatic reactions. If the flow of nutrients in any one part of this network is reduced or disrupted, then changes in another part of the network can occur in response in order for this first change to be somehow balanced or compensated. Moreover, both catabolic and anabolic reactions are adjusted in such a way that they proceed in the most economical way, that is, with the least expenditure of energy and substances. For example, the oxidation of nutrients in the cell occurs at a rate just sufficient to satisfy its energy needs at the moment.

Specific and general pathways of catabolism

There are three stages in catabolism:

1. Polymers are converted into monomers (proteins into amino acids, carbohydrates into monosaccharides, lipids into glycerol and fatty acids). The chemical energy is dissipated in the form of heat.

2. Monomers are converted into common products, the vast majority into acetyl-CoA. Chemical energy is partly dissipated in the form of heat, partly accumulated in the form of reduced coenzyme forms (NADH, FADH2), partly stored in macroergic bonds of ATP (substrate phosphorylation).

The 1st and 2nd stages of catabolism refer to specific pathways that are unique to the metabolism of proteins, lipids and carbohydrates.

3. The final stage of catabolism is reduced to the oxidation of acetyl-CoA to CO 2 and H 2 O in the reactions of the tricarboxylic acid cycle (Krebs cycle) - the general path of catabolism. Oxidative reactions of the general path of catabolism are associated with a chain of tissue respiration. At the same time, energy (40–45%) is stored in the form of ATP (oxidative phosphorylation).

As a result of specific and general pathways of catabolism, biopolymers (proteins, carbohydrates, lipids) break down to CO 2 , H 2 O and NH 3 , which are the main end products of catabolism.

Metabolites in normal and pathological conditions

Levels of study of metabolism

Levels of study of metabolism:

1. The whole organism.

2. Isolated organs (perfused).

3. Sections of tissues.

4. Cell cultures.

5. Tissue homogenates.

6. Isolated cell organelles.

7. Molecular level (purified enzymes, receptors, etc.).

Rice. 8.1. Diagram of specific and general pathways of catabolism

Chapter 9

A cell is a biological system based on membrane structures that separate the cell from the external environment, form its compartments (compartments), as well as ensure the intake and removal of metabolites, the perception and transmission of signals, and are the structural organizers of metabolic pathways.

The coordinated functioning of membrane systems - receptors, enzymes, transport mechanisms helps maintain cell homeostasis and at the same time quickly respond to changes in the external environment.

Membranes are non-covalent supramolecular structures. The proteins and lipids in them are held together by a variety of non-covalent interactions (cooperative in nature).

The main functions of membranes include:

1. separation of the cell from the environment and the formation of intracellular compartments (compartments);

2. control and regulation of the transport of a huge variety of substances through membranes (selective permeability);

3. participation in providing intercellular interactions;

4. perception and signal transmission inside the cell (reception);

5. localization of enzymes;

6. energy-transforming function.

The membranes are asymmetric in structural and functional respects (carbohydrates are always localized on the outside and they are not on the inside of the membrane). These are dynamic structures: the proteins and lipids that make up them can move in the plane of the membrane (lateral diffusion). However, there is also a transition of proteins and lipids from one side of the membrane to the other (transverse diffusion, flip-flop), which occurs extremely slowly. The mobility and fluidity of membranes depend on its composition: the ratio of saturated and unsaturated fatty acids, as well as cholesterol. The lower the membrane fluidity, the higher the saturation of fatty acids in phospholipids and the higher the cholesterol content. In addition, membranes are characterized by self-assembly.

General properties cell membranes:

1. easily permeable to water and neutral lipophilic compounds;

2. less permeable to polar substances (sugars, amides);

3. poorly permeable to small ions (Na + , Cl - etc.);

4. characterized by high electrical resistance;

5. asymmetry;

6. can spontaneously restore integrity;

7. liquidity.

Chemical composition of membranes.

The membranes are composed of lipid and protein molecules, the relative amount of which varies widely in different membranes. Carbohydrates are contained in the form of glycoproteins, glycolipids and make up 0.5% -10% of the membrane substances. According to the fluid mosaic model of the membrane structure (Senger and Nicholson, 1972), the basis of the membrane is a lipid bilayer, in the formation of which phospholipids and glycolipids participate. The lipid bilayer is formed by two rows of lipids, the hydrophobic radicals of which are hidden inside, and the hydrophilic groups are turned outward and are in contact with the aqueous medium. Protein molecules are, as it were, dissolved in the lipid bilayer and relatively freely "float in the lipid sea in the form of icebergs on which glycocalyx trees grow."

membrane lipids.

Membrane lipids are amphiphilic molecules, i.e. the molecule contains both hydrophilic groups (polar heads) and aliphatic radicals (hydrophobic tails), which spontaneously form a bilayer in which the lipid tails face each other. The thickness of one lipid layer is 2.5 nm, of which 1 nm falls on the head and 1.5 nm on the tail. There are three main types of lipids in membranes: phospholipids, glycolipids, and cholesterol. The mean cholesterol/phospholipid molar ratio is 0.3–0.4, but in the plasma membrane this ratio is much higher (0.8–0.9). The presence of cholesterol in membranes reduces the mobility of fatty acids, reduces the lateral diffusion of lipids and proteins.

Phospholipids can be divided into glycerophospholipids and sphingophospholipids. The most common membrane glycerophospholipids are phosphatidylcholines and phosphatidylethanolamines. Each glycerophospholipid, such as phosphatidylcholine, is represented by several dozen phosphatidylcholines that differ from each other in the structure of fatty acid residues.

Glycerophospholipids account for 2–8% of all membrane phospholipids. The most common are phosphatidylinositols.

Specific phospholipids of the inner mitochondrial membrane, cardiolipins (diphosphatide glycerols), built on the basis of glycerol and two phosphatidic acid residues, account for about 22% of all mitochondrial membrane phospholipids.

The myelin sheath of nerve cells contains significant amounts of sphingomyelins.

Membrane glycolipids are represented by cerebrosides and gangliosides, in which the hydrophobic part is represented by ceramide. The hydrophilic group - a carbohydrate residue - is attached by a glycosidic bond to the hydroxyl group of the first carbon atom of ceramide. In significant quantities, glycolipids are found in the membranes of brain cells, epithelium and erythrocytes. Gangliosides of erythrocytes of different individuals differ in the structure of oligosaccharide chains and exhibit antigenic properties.

Cholesterol is present in all membranes of animal cells. Its molecule consists of a rigid hydrophobic core and a flexible hydrocarbon chain, the only hydroxyl group is the polar head.

Functions of membrane lipids.

Phospho- and glycolipids of membranes, in addition to participating in the formation of the lipid bilayer, perform a number of other functions. Membrane lipids form an environment for the functioning of membrane proteins, which adopt a native conformation in it.

Some membrane lipids are precursors of second messengers in the transmission of hormonal signals. So phosphatidylinositol diphosphate under the action of phospholipase C is hydrolyzed to diacylglycerol and inositol triphosphate, which are second messengers of hormones.

A number of lipids are involved in the fixation of anchored proteins. An example of an anchored protein is acetylcholinesterase, which is fixed on the postsynaptic membrane to phosphatitylinositol.

Membrane proteins.

Membrane proteins are responsible for the functional activity of membranes and account for 30 to 70% of them. Membrane proteins differ in their position in the membrane. They can penetrate deeply into the lipid bilayer or even penetrate it - integral proteins, attach to the membrane in various ways - surface proteins, or covalently contact with it - anchored proteins. Surface proteins are almost always glycosylated. Oligosaccharide residues protect the protein from proteolysis and are involved in ligand recognition and adhesion.

Proteins localized in the membrane perform structural and specific functions:

1. transport;

2. enzymatic;

3. receptor;

4. antigenic.

Mechanisms of membrane transport of substances

There are several ways of transporting substances through the membrane:

1. Simple diffusion- this is the transfer of small neutral molecules along the concentration gradient without the expenditure of energy and carriers. The easiest way to pass by simple diffusion through the lipid membrane is small non-polar molecules, such as O 2, steroids, thyroid hormones. Small polar uncharged molecules - CO 2 , NH 3 , H 2 O, ethanol and urea - also diffuse at a sufficient rate. Diffusion of glycerol is much slower, and glucose is practically unable to pass through the membrane on its own. For all charged molecules, regardless of size, the lipid membrane is impermeable.

2. Facilitated diffusion- transfer of a substance along a concentration gradient without energy expenditure, but with a carrier. characteristic of water-soluble substances. Facilitated diffusion differs from simple diffusion by a higher transfer rate and the ability to saturate. There are two types of facilitated diffusion:

Transport through special channels formed in transmembrane proteins (for example, cation-selective channels);

With the help of translocase proteins that interact with a specific ligand, they ensure its diffusion along a concentration gradient (ping-pong) (transfer of glucose into erythrocytes using the GLUT-1 carrier protein).

Kinetically, the transfer of substances by facilitated diffusion resembles an enzymatic reaction. For translocases, there is a saturating concentration of the ligand, at which all the binding sites of the protein with the ligand are occupied, and the proteins work at maximum speed. Therefore, the rate of transport of substances by facilitated diffusion depends not only on the concentration gradient of the transported substance, but also on the number of carrier backs in the membrane.

Simple and facilitated diffusion refers to passive transport, as it occurs without energy consumption.

3. Active transport- transport of a substance against a concentration gradient (uncharged particles) or an electrochemical gradient (for charged particles), requiring energy, most often ATP. There are two types of it: primary active transport uses the energy of ATP or redox potential and is carried out with the help of transport ATPases. The most common in the plasma membrane of human cells are Na +, K + - ATP-ase, Ca 2+ -ATP-ase, H + -ATP-ase.

In secondary active transport, an ion gradient is used, created on the membrane due to the operation of the primary active transport system (glucose absorption by intestinal cells and reabsorption of glucose and amino acids from primary urine by kidney cells, carried out when Na + ions move along the concentration gradient).

Transfer of macromolecules across the membrane. Transport proteins transport small, polar molecules across the cell membrane, but they cannot transport macromolecules such as proteins, nucleic acids, polysaccharides, or individual particles.

The mechanisms by which cells can take up such substances or remove them from the cell are different from the mechanisms by which ions and polar compounds are transported.

1. Endocytosis. This is the transfer of a substance from the environment into the cell along with part of the plasma membrane. By endocytosis (phagocytosis), cells can engulf large particles such as viruses, bacteria, or cell fragments. The absorption of liquid and substances dissolved in it with the help of small bubbles is called pinocytosis.

2. Exocytosis. Macromolecules, such as plasma proteins, peptide hormones, digestive enzymes, are synthesized in cells and then secreted into the extracellular space or blood. But the membrane is not permeable to such macromolecules or complexes; their secretion occurs by exocytosis. The body has both regulated and unregulated pathways of exocytosis. Unregulated secretion is characterized by continuous synthesis of secreted proteins. An example is the synthesis and secretion of collagen by fibroblasts to form the extracellular matrix.

Regulated secretion is characterized by the storage of molecules prepared for export in transport vesicles. With the help of regulated secretion, the release of digestive enzymes, as well as the secretion of hormones and neurotransmitters.

Chapter 10 biological oxidation

From the point of view of thermodynamics, living organisms are open systems. An exchange of energy is possible between the system and the environment, which occurs in accordance with the laws of thermodynamics. Each organic compound that enters the body has a certain amount of energy (E). Some of this energy can be used to do useful work. Such energy is called free energy (G). The direction of a chemical reaction is determined by the DG value. If this value is negative, then the reaction proceeds spontaneously. Such reactions are called exergonic. If DG is positive, then the reaction will proceed only when free energy comes from outside - these are endergonic reactions. In biological systems, thermodynamically unfavorable endergonic reactions can proceed only at the expense of the energy of exergonic reactions. Such reactions are called energetically coupled.

The most important function of many biological membranes is the transformation of one form of energy into another. Membranes with such functions are called energy-converting. Any membrane that performs an energy function is capable of converting the chemical energy of oxidized substrates or ATP into electrical energy, namely, into a transmembrane electric potential difference (DY) or into the energy of a difference in concentrations of substances contained in solutions separated by a membrane, and vice versa. Among the energy-converting membranes having highest value, we can name the inner membrane of mitochondria, the outer cytoplasmic membrane, the membranes of lysosomes and the Golgi complex, the sarcoplasmic reticulum. The outer membrane of the mitochondria and the nuclear membrane cannot convert one form of energy into another.

Energy conversion in a living cell is described by the following general scheme:

Energy resources → ΔμI → work

where ΔμI is the transmembrane difference of the electrochemical potentials of the ion I. Consequently, the processes of energy utilization and performance of work due to it are coupled through the formation and use of ΔμI. Therefore, this ion can be called a conjugating ion. The main conjugating ion in the eukaryotic cell is H + , and accordingly ΔμH + is the main convertible form of energy storage. The second most important conjugating ion is Na + (ΔμNa +). While Ca 2+ , K + and Cl - are not used to do any work.

Biological oxidation is the process of dehydrogenation of a substrate with the help of intermediate hydrogen carriers and its final acceptor. If oxygen acts as the final acceptor, the process is called aerobic oxidation or tissue respiration, if the final acceptor is not oxygen - anaerobic oxidation. Anaerobic oxidation is of limited importance in the human body. The main function of biological oxidation is to provide the cell with energy in an accessible form.

Tissue respiration is the process of hydrogen oxidation with oxygen to water by the enzymes of the tissue respiration chain. It proceeds according to the following scheme:

A substance is oxidized if it donates electrons or simultaneously electrons and protons (hydrogen atoms), or attaches oxygen. The ability of a molecule to donate electrons to another molecule is determined by the redox potential (redox potential). Any compound can only donate electrons to a substance with a higher redox potential. An oxidizing agent and a reducing agent always form a conjugated pair.

There are 2 types of oxidizable substrates:

1. Pyridine-dependent - alcohol or aldehyde - isocitrate, α-ketoglutarate, pyruvate, malate, glutamate, β-hydroxyacyl-CoA, β-hydroxybutyrate - NAD-dependent dehydrogenases participate in their dehydrogenation.

2. flavin-dependent - are derivatives of hydrocarbons - succinate, acyl-CoA, glycerol-3-phosphate, choline - when dehydrogenated, they transfer hydrogen to FAD-dependent dehydrogenases.

The tissue respiration chain is a sequence of carriers of hydrogen protons (H+) and electrons from an oxidized substrate to oxygen localized on the inner membrane of mitochondria.

Rice. 10.1. Scheme of the CTD

CTD components:

1. NAD-dependent dehydrogenases dehydrate pyridine-dependent substrates and accept 2ē and one H + .

2. FAD (FMN) - dependent dehydrogenases accept 2 hydrogen atoms (2H + and 2ē). FMN-dependent dehydrogenase only dehydrates NADH, while FAD dehydrogenases oxidize flavin-dependent substrates.

3. Fat-soluble carrier ubiquinone (coenzyme Q, CoQ) - freely moves along the mitochondrial membrane and accepts two hydrogen atoms and turns into CoQH 2 (reduced form - ubiquinol).

4. Cytochrome system - transfers only electrons. Cytochromes are iron-containing proteins whose prosthetic group resembles heme in structure. In contrast to heme, the iron atom in cytochrome can reversibly change from two to the trivalent state (Fe 3+ + ē → Fe 2+). This ensures the participation of cytochrome in electron transport. Cytochromes act in ascending order of their redox potential and are located in the respiratory chain as follows: b-c 1 -c-a-a 3. The last two work in association as one enzyme, cytochrome oxidase aa 3 . Cytochrome oxidase consists of 6 subunits (2 - cytochrome a and 4 - cytochrome a 3). In cytochrome a 3, in addition to iron, there are copper atoms and it transfers electrons directly to oxygen. In this case, the oxygen atom becomes negatively charged and acquires the ability to interact with protons to form metabolic water.

Iron-sulfur proteins (FeS) contain non-heme iron and are involved in redox processes proceeding by a one-electron mechanism and are associated with flavoproteins and cytochrome b.

Structural organization of the tissue respiration chain

The components of the respiratory chain in the inner membrane of micochondria form complexes:

1. Complex I (NADH-CoQH 2 -reductase) - accepts electrons from mitochondrial NADH and transports them to CoQ. Protons are transported into the intermembrane space. FMN and iron-sulfur proteins are intermediate acceptors and carriers of protons and electrons. Complex I separates the flow of electrons and protons.

2. Complex II - succinate - KoQ - reductase - includes FAD-dependent dehydrogenases and iron-sulfur proteins. It transports electrons and protons from flavin-dependent substrates to ubiquinone, with the formation of an intermediate FADH 2 .

Ubiquinone easily moves across the membrane and transfers electrons to complex III.

3. Complex III - CoQH 2 - cytochrome c - reductase - contains cytochromes b and c 1, as well as iron-sulfur proteins. The functioning of CoQ with complex III leads to separation of the flow of protons and electrons: protons from the matrix are pumped into the intermembrane space of mitochondria, and electrons are transported further along the CTD.

4. Complex IV - cytochrome a - cytochrome oxidase - contains cytochrome oxidase and transports electrons to oxygen from the intermediate carrier of cytochrome c, which is a mobile component of the chain.

There are 2 types of CTD:

1. Complete chain - pyridine-dependent substrates enter it and betray hydrogen atoms to NAD-dependent dehydrogenases

2. Incomplete (shortened or reduced) CTD in which hydrogen atoms are transferred from FAD-dependent substrates, bypassing the first complex.

Oxidative phosphorylation of ATP

Oxidative phosphorylation is the process of ATP formation, coupled with the transport of electrons along the tissue respiration chain from the oxidized substrate to oxygen. Electrons always tend to move from electronegative to electropositive systems, so their transport through the CTD is accompanied by a decrease in free energy. In the respiratory chain, at each stage, the decrease in free energy occurs in steps. In this case, three sections can be distinguished in which the electron transfer is accompanied by a relatively large decrease in the free energy. These steps are able to provide energy for the synthesis of ATP, since the amount of free energy released is approximately equal to the energy required for the synthesis of ATP from ADP and phosphate.

To explain the mechanisms of conjugation of respiration and phosphorylation, a number of hypotheses have been put forward.

Mechanochemical or conformational (Green-Boyer).

During the transfer of protons and electrons, the conformation of enzyme proteins changes. They go into a new, energy-rich conformational state, and then, when they return to their original conformation, give energy for the synthesis of ATP.

Hypothesis of chemical conjugation (Lipman).

"Coupling" substances are involved in the conjugation of respiration and phosphorylation. They accept protons and electrons and interact with H 3 RO 4 . At the moment of donation of protons and electrons, the bond with phosphate becomes macroergic and the phosphate group is transferred to ADP with the formation of ATP by substrate phosphorylation. The hypothesis is logical, but "coupling" substances have not yet been isolated.

Chemiosmotic hypothesis by Peter Mitchell (1961)

The main postulates of this theory:

1. the inner membrane of mitochondria is impermeable to H + and OH − ions;

2. due to the energy of electron transport through complexes I, III and IV of the respiratory chain, protons are pumped out of the matrix;

3. the electrochemical potential arising on the membrane is an intermediate form of energy storage;

4. The return of protons to the mitochondrial matrix through the proton channel of ATP synthase is the energy supplier for ATP synthesis according to the scheme

ADP + H 3 RO 4 → ATP + H 2 O

Evidence for the chemioosmotic theory:

1. there is an H + gradient on the inner membrane and it can be measured;

2. the creation of an H + gradient in mitochondria is accompanied by ATP synthesis;

3. ionophores (uncouplers) that destroy the proton gradient and inhibit the synthesis of ATP;

4. inhibitors that block the transport of protons through the proton channels of ATP synthase inhibit the synthesis of ATP.

The structure of ATP synthase

ATP synthase is an integral protein of the inner membrane of mitochondria. It is located in close proximity to the respiratory chain and is referred to as complex V. ATP synthase consists of 2 subunits, referred to as F 0 and F 1 . The hydrophobic F0 complex is immersed in the inner mitochondrial membrane and consists of several protomers that form a channel through which protons are transferred to the matrix. The F 1 subunit protrudes into the mitochondrial matrix and consists of 9 protomers. Moreover, three of them bind the F 0 and F 1 subunits, forming a kind of leg and are sensitive to oligomycin.

The essence of the chemioosmotic theory: due to the energy of electron transfer along the CTD, protons move through the inner mitochondrial membrane into the intermembrane space, where an electrochemical potential (ΔμH +) is created, which leads to a conformational rearrangement of the active center of ATP synthase, as a result of which the reverse transport of protons becomes possible through the proton channels of ATP synthase. When the protons return back, the electrochemical potential is transformed into the energy of the macroergic bond of ATP. The resulting ATP, with the help of the translocase carrier protein, moves to the cytosol of the cell, and in return ADP and Fn enter the matrix.

The phosphorylation coefficient (P/O) is the number of inorganic phosphate atoms included in ATP molecules, calculated per one atom of absorbed oxygen used.

Phosphorylation sites are sites in the respiratory chain where the energy of electron transport is used to generate a proton gradient, and then stored in the form of ATP during phosphorylation:

1. 1 point - between pyridine-dependent and flavin-dependent dehydrogenases; 2 point - between cytochromes b and c 1; 3 point - between cytochromes a and a 3.

2. Consequently, during the oxidation of NAD-dependent substrates, the P/O coefficient is 3, since electrons from NADH are transported with the participation of all CTD complexes. Oxidation of FAD-dependent substrates bypasses complex I of the respiratory chain and P/O is 2.

Energy metabolism disorders

All living cells constantly need ATP for various activities. Violation of any stage of metabolism, leading to the cessation of ATP synthesis, is fatal to the cell. Tissues with high energy requirements (CNS, myocardium, kidneys, skeletal muscles and liver) are the most vulnerable. Conditions in which ATP synthesis is reduced are combined by the term "hypoenergetic". The causes of these conditions can be divided into two groups:

Alimentary - starvation and hypovitaminosis B2 and PP - there is a violation of the supply of oxidizable substrates in the CTD or the synthesis of coenzymes.

Hypoxic - occur when there is a violation of the delivery or utilization of oxygen in the cell.

CTD regulation.

It is carried out with the help of respiratory control.

Respiratory control is the regulation of the rate of electron transfer along the respiratory chain by the ratio of ATP/ADP. The lower this ratio, the more intense respiration and the more actively ATP is synthesized. If ATP is not used, and its concentration in the cell increases, then the flow of electrons to oxygen stops. Accumulation of ADP increases substrate oxidation and oxygen uptake. The mechanism of respiratory control is characterized by high precision and is important, since as a result of its action, the rate of ATP synthesis corresponds to the energy needs of the cell. There are no reserves of ATP in the cell. The relative concentrations of ATP/ADP in tissues vary within narrow limits, while the energy consumption of a cell can vary by dozens of times.

American biochemist D. Chance proposed to consider 5 states of mitochondria, in which the rate of their respiration is limited by certain factors:

1. Lack of SH 2 and ADP - the rate of respiration is very low.

2. Lack of SH 2 in the presence of ADP - the speed is limited.

3. There is SH 2 and ADP - respiration is very active (it is limited only by the speed of transport of ions through the membrane).

4. Lack of ADP in the presence of SH 2 - breathing is inhibited (state of respiratory control).

5. Lack of oxygen, in the presence of SH 2 and ADP - a state of anaerobiosis.

Mitochondria in a resting cell are in state 4, in which the rate of respiration is determined by the amount of ADP. During intensive work, they can be in state 3 (the possibilities of the respiratory chain are exhausted) or 5 (lack of oxygen) - hypoxia.

CTD inhibitors are drugs that block the transfer of electrons through the CTD. These include: barbiturates (amytal), which block the transport of electrons through complex I of the respiratory chain, the antibiotic antimycin blocks the oxidation of cytochrome b; carbon monoxide and cyanides inhibit cytochrome oxidase and block the transport of electrons to oxygen.

Inhibitors of oxidative phosphorylation (oligomycin) are substances that block the transport of H + through the proton channel of ATP synthase.

Uncouplers of oxidative phosphorylation (ionophores) are substances that suppress oxidative phosphorylation without affecting the process of electron transfer through CTD. The mechanism of action of uncouplers is that they are fat-soluble (lipophilic) substances and have the ability to bind protons and transfer them through the inner mitochondrial membrane to the matrix, bypassing the proton channel of ATP synthase. The energy released in this process is dissipated in the form of heat.

Artificial uncouplers - dinitrophenol, vitamin K derivatives (dicumarol), some antibiotics (valinomycin).

Natural uncouplers - products of lipid peroxidation, long chain fatty acids, large doses of iodine-containing hormones thyroid gland, thermogenin proteins.

The thermoregulatory function of tissue respiration is based on the uncoupling of respiration and phosphorylation. Mitochondria of brown adipose tissue produce more heat, since the protein thermogenin present in them uncouples oxidation and phosphorylation. It is essential in maintaining the body temperature of newborns.

Biochemical ways of adaptation of animals and humans to geochemical environmental conditions is not a question of individual isolated organisms, but of the adaptability of individuals within a population as part of it. Not only the population, but also the individual must be considered as physiological and genetic units of the evolutionary process, occupying different levels in the structure of the biosphere. The study of the intrapopulation variability of organisms reveals the role of the population in the evolution of individual individuals and, in turn, individual individuals in the evolution of the population as a whole.

The significance of the natural geochemical environment for the development of organisms and the evolution of life is determined by the use by organisms of many chemical elements in the processes of metabolism and biologically active compounds that include these elements. Therefore, the heterogeneity of the geochemical environment is one of the important reasons for the variability of metabolism and the synthesis of biologically active compounds in organisms.

Modern biogeochemistry, geochemistry, and soil science have clearly proven the geochemical heterogeneity of the biosphere, the significant chemical variability of the living environment under the conditions of the lithosphere, hydrosphere, and troposphere. Organisms are intimately connected to the geochemical environment. They absorb from this environment all the available chemical elements that form soluble compounds, or actively convert insoluble compounds into available ones.

A very important property of the biosphere is the unity of the geochemical environment and life, which has developed during the evolution of the biosphere and is expressed by the constant dependence of life on the geochemical conditions of the environment and climate (water regime, temperature, insolation, convection). The degree of accumulation of chemical elements by organisms is determined not only by the geochemistry of the environment and the biological nature of organisms, but also by biogeochemical food chains, consisting of a system of interdependent links through which organisms and the environment are connected (soil-forming rocks, soils, waters, air, microorganisms, plants, animals, etc.). Human).

To elucidate the complex ways of adaptation of organisms to the geochemical environment, it is necessary to determine the general laws governing the action of various concentrations of chemical elements on the organism. It has been established that both with a deficiency and an excess of cobalt, copper, zinc in the diet, the weight gain of animals decreases. The synthesis of many biologically active compounds in the body also depends on the content of certain trace elements in the diet or geochemical environment. The accumulation of vitamin B 12 in the liver of animals (sheep, cattle, rabbits, and others) is significantly reduced with a decrease in the amount of cobalt in the medium or diet and its slightly high content. Lack of iodine or its excess leads to a compensatory increase in the size of the thyroid gland and inhibition of the synthesis of iodine-containing compounds in it: iodotyrosines, iodothyronines, thyroxine and their derivatives. Molybdenum and copper are important regulators of purine metabolism. With a relative deficiency or excess of molybdenum in humans and animals, the synthesis is inhibited or the activity of the enzyme xanthine oxidase containing molybdenum, which converts some purine bases into uric acid, is inhibited, and in animals with a low, as well as with an increased amount of copper, the synthesis of urate oxidase, which oxidizes uric acid into allantoin, decreases. . Many such examples could be cited. In all cases, the same regularity is observed: a lack or excess in the environment or diet of certain chemical elements inhibits certain biochemical processes in the body. Consequently, the level of synthesis of enzymes and other biologically active compounds in the body, which ensures the normal course of life processes, is observed only at certain concentrations and ratios of microelements in the environment and body (figure). Regulatory systems of the body (deposit, excretory, barrier, synthesis of biologically active compounds, and others) cannot function normally when the concentration of trace elements is above or below these limits.

In such cases, dysfunction or disruption occurs, dysfunctions, developmental and metabolic anomalies occur, which “can lead to the appearance of endemic diseases in humans and animals.

We consider individual reactions to a lack or excess of trace elements as part of the whole. To understand these phenomena, it is necessary to find out the main points of application of chemical elements to biochemical processes and to establish a chain of processes involving the whole organism in reactions to a deficiency or excess of certain elements, i.e., to explain the significance of a part in the reaction of the whole. For example, the main role of cobalt in the body is in the microbial synthesis in the digestive tract of vitamin B 12 containing cobalt.

With a lack of cobalt, the synthesis of vitamin B 1 2 and its absorption through the intestinal mucosa can be significantly weakened. The weakening of the process of absorption of vitamin B 12 is due to a decrease in the secretion of gastric juice and a lack of mucoprotein, which gives a compound with vitamin B 12, for which the intestinal mucosa is permeable. There is still no clarity on the significance of the formation of its connection with zinc for the absorption of vitamin B 12. Due to the lack of vitamin B 12 in the body, its deposition by the liver and other organs decreases. This is especially pronounced in ruminants (sheep, cattle), in which cobalt deficiency causes disease with endemic hypo- and avitaminosis B 12 , but it is quite clearly manifested in other groups (rabbits, pigs). With a lack of vitamin B 12 in the body, pernicious anemia develops. In addition, the synthesis of the isomerase coenzyme, which acts on methylmalonic acid, is inhibited, and the methylation of thymine and methionine is disturbed. Violation of such important processes in the body leads to the inclusion in the pathological process of more and more new links of metabolism. Cobalt deficiency causes a weakening of the synthesis of proteins, nucleic acids (for example, thymonucleic acid), a decrease in the activity of many enzymes (for example, arginase), including nucleic metabolism enzymes (DNAases), a decrease in basal metabolism, and weight loss in animals. The importance of cobalt in metabolic processes has not yet been sufficiently studied. But there is no doubt that cobalt deficiency can lead to profound changes in the whole organism.

At low concentrations of copper in environment and diet in animals, characteristic changes in metabolism are observed, caused by a decrease in the activity of oxidative enzymes containing copper or iron. This is especially clearly manifested in the biogeochemical provinces of endemic ataxia, in which a lack of copper is combined with an excess of molybdenum and sulfates. With a lack of copper, inhibition of cytochrome oxidase in rats is more pronounced in the liver, in pigs and chickens - in the heart, in sheep - in the brain, and inhibited succinate dehydrogenases in sheep - in the white matter of the brain and spinal cord; inhibition of the activity of NAD-cytochrome-c-reductase was found in the mitochondria of the liver of rats, sulfide oxidase - in the liver of sheep, DOPA-oxidase - in the liver and gray matter of the brain and spinal cord of sheep, monoamine oxidase in pigs and sheep - in the blood serum, in chickens - in aorta; the activity of isocitrate dehydrogenase of rat liver mitochondria increases with copper deficiency, since, apparently, copper easily inhibits this enzyme; with a lack of copper and an increased content of molybdenum, the activity of purine metabolism enzymes - xanthine oxidase and urate oxidase - in various types of mammals increases.

The data presented on the effect of copper deficiency on the activity of many enzymes of various organs and tissues show the importance of comparative physiological studies.

A change in the activity of the enzymes of an animal organism with a lack of copper entails a violation of many biochemical processes and physiological states. It is very likely that sulfides formed in the liver during the breakdown of pyreine and in the rumen of ruminants as a result of microbiological reduction of sulfates are important toxic agents in the body with a lack of copper. With an excess of sulfates in the diet, sulfides are formed, while food copper turns into sulfur, which is not absorbed by the body, which increases copper deficiency. Neutralization of a large part of sulfides occurs in the liver by their oxidation to thiosulfate and sulfate. The oxidation of sulfides to thiosulfate is carried out by liver sulfide oxidase, the activity of which is inhibited by a low content of copper in the diet and an excess of molybdenum. Obviously, with copper deficiency, the formation of sulfides in the tissues increases, and an excess of sulfides further enhances it. Experiments with radioactive copper suggest that in biogeochemical provinces, with a lack of copper and an excess of molybdenum and sulfates, the loss of copper by tissues increases, which also increases the deficiency of this microelement.

Copper deficiency, by changing the activity of many enzymes, causes significant metabolic disorders, for example, lipid metabolism (decrease in the level of sphingomyelin and acetalphosphatides in the white matter of the brain and spinal cord, impaired myelination of the central nervous system), chromoproteins (a drop in hemoglobin concentration, partly due to with a delay in the maturation of erythrocytes and a decrease in their life expectancy), the synthesis of elastin and collagen (damage to the connective tissue, rupture of the aorta and heart vessels), purine metabolism (an increase in the activity of xanthine oxidase, the formation of uric acid, an increase in the activity of urate oxidase), inhibition of the oxidation of most substrates of the tricarboxylic cycle acids (citrate, malate, a-ketoglutarate, pyruvate and others).

The study of the main role of metals in the metabolism of an animal organism is an important way of studying the influence of the geochemical environment on an animal organism. In biogeochemical provinces with an excess of molybdenum, the action of this metal is associated with an increase in the synthesis of xanthine oxidase and an increase in its activity; in provinces enriched with boron, proteinases and amylases of the digestive tract are partially inhibited; lack of iodine limits the synthesis of thyroid hormones; lack or excess of cobalt, as well as manganese, delay the use of iodine in the synthesis of triiodothyronines and thyroxine. These primary effects of metals on metabolic processes cause secondary dysfunctions of many biochemical and physiological processes.

An assessment of the possibility of metabolic disorders or, in general, the appearance of biological effects under the influence of geochemical environmental factors should be based on quantitative parameters. Therefore, an important task of geochemical ecology is to determine the boundaries of the concentration of chemical elements in soils, fodder plants, food rations, within which the normal development and life of animal organisms is ensured, as well as to determine the threshold concentrations at which the course of life processes is disturbed.

Knowledge of soil and food threshold concentrations of chemical elements makes it possible to represent the geographical variability of metabolism in an animal organism depending on the conditions of the geochemical environment and can be the basis for biogeochemical zoning.

We divided the biosphere corresponding to the territory of the USSR into regions called biogeochemical zones. They are determined by the unity of soil-forming processes, climatic factors, biogenic migration of chemical elements, and the nature of biological reactions of organisms to geochemical and physical environmental factors.

Zonal regions of the biosphere are divided into subregions - zonal biogeochemical provinces, in which the signs of zones are combined in terms of concentration and ratio of chemical elements, and azonal, the signs of which do not correspond to the characteristics of the zones. We have compiled a schematic map of the biogeochemical zones and provinces of the USSR, which shows areas of characteristic changes in metabolism and the spread of a number of endemic diseases in humans and animals, as well as areas of exacerbation of natural selection under the influence of a lack or excess of microelements. The synthesis of oxidative enzymes in animal organisms under the conditions of the chernozem zone is more pronounced than in the non-chernozem zone; in the provinces of endemic ataxia in Dagestan, Uzbekistan and in the Aktobe region, the most pronounced inhibition of the synthesis of oxidative enzymes is observed; vitamin Bi 2 is deposited in the animal body more strongly in the chernozem zone compared to the non-chernozem zone (especially the deposition of vitamin B, 2 in the liver and muscles is reduced in areas of sandy soils); the synthesis of iodine compounds of the thyroid gland is weakened in the non-chernozem zone and mountain zones, as well as in the floodplain of rivers in other zones; the synthesis of xanthine oxidase is enhanced under the conditions of the molybdenum provinces of Armenia; urate oxidase is more active in animals in provinces with high copper content; In some cases, proteinases and amylases are inhibited to varying degrees in the boron provinces of the dry steppe, semidesert, and desert biogeochemical zones.

To analyze the variability of animal metabolism, it is necessary to take into account not only the variability of individual individuals, but the population as a whole, consisting of individuals of the same species, it is necessary to determine the structure of the population using the physiological, biogeochemical and morphological characteristics of individuals. In this case, individual variability should be considered as a component of population variability. This will allow us to distinguish groups of organisms with different sensitivity to extreme geochemical factors within the population. This creates the opportunity to observe patterns of variability in populations of one species under different conditions of the geochemical environment - with a lack, excess or normal content of chemical elements in soils, waters, plants, feed, food rations.

The variability of the threshold sensitivity of animals to the geochemical environment (copper, molybdenum, boron, strontium, uranium, and others) we have extensively studied. Intrapopulation physiological and biochemical variability of organisms determines the degree of exacerbation of natural selection and the degree of adaptation of the organism to extreme conditions. It can be assumed that significant reserves of potential latent variability accumulate in animal populations, apparently due to small mutations of genes and their recombinations. We found such reserves of variability in soil microorganisms living in conditions of high concentrations of certain chemical elements (molybdenum, vanadium, boron, selenium, cobalt). Intrapopulation variability of microorganisms was determined in our laboratory on a physiological basis - the adaptability of organisms of individual strains isolated from one colony to various possible natural concentrations of chemical elements (from minimum to maximum). For example, strains of Bacillus megaterium from soils rich in uranium grow well at high concentrations of this element and develop poorly at low concentrations. On the contrary, bacteria of the same species, isolated from soils poor in uranium, cannot develop at high concentrations. This is a general rule for various types of microorganisms and chemical elements. The same patterns of growth of bacteria and a number of actinomycetes under the conditions of boron provinces when compared with the same species taken from soils poor in boron. Among the studied strains, mutants were found that do not obey the general rules - isolated from soils rich in boron, but growing well at any concentration. By introducing DNA from mutant forms and forms adapted to high concentrations of boron into cultures of microorganisms isolated from soils poor in boron, it is possible to obtain a genetic transformation of their adaptability to boron - forms that grow well at high concentrations of boron. Genetic transformation was also carried out in Bacillus megaterium living at low selenium concentrations using DNA isolated from forms of the selenium province. From those unadapted to selenium, forms were obtained that developed well at high concentrations of selenium. At the same time, it is necessary to point out that a protective enzyme, selenium reductase, was found in these bacteria from the selenium provinces, which reduces selenites to elemental indigestible selenium. In forms of the same species isolated from soils poor in selenium, this enzyme was not found. Genetic transformation leads to the appearance of the enzyme in forms that have not synthesized it before.

With the help of genetic transformation, the hereditary nature of the adaptability of microorganisms to extreme conditions of the chemical environment is shown. It can be assumed that in biogeochemical provinces rich or poor in certain chemical elements, mutations induced by extreme factors occur. There is an enrichment of the gene pool of the population, which creates conditions for the aggravation of natural selection and speciation, the transformation of the genetic and ecological structures of the population under extreme changes in the conditions of the geochemical environment.

The variability of microbial populations and their genetic nature can be studied (with a successful choice of natural objects) using conventional microbiological methods (experimental geochemical ecology of microorganisms), while such studies on plant and animal organisms require the conditions of phyto- and zootrons, where it is possible to regulate chemical and physical environmental factors. The geochemical ecology of organisms should not only observe natural phenomena - the influence of the environment and communities on organisms, but should develop as an experimental science (experimental geochemical ecology).

We have considered some issues of geochemical ecology at the level of individuals and populations. The geochemical environment acts on organisms at all levels of the biosphere structure, at the level of regions of the biosphere (biogeochemical zones) and subregions (biogeochemical provinces) of biogeocenoses, populations, and individuals.

Research in the field of geochemical ecology, the establishment of causal relationships is impossible without the study of organs and tissues (the concentration of chemical elements and the effect of the degree of their accumulation on the intermediate metabolism, activity and synthesis of biologically active compounds, especially enzymes). Such studies, as well as those conducted at the cellular, subcellular and molecular levels, are the basis for understanding the relationship of organisms with the geochemical environment and the adaptation of organisms to geochemical environmental factors. An example of the study of issues of geochemical ecology at molecular level can serve as an analysis of the effect on the body of various concentrations and ratios of copper and molybdenum. At high concentration in diet animals of molybdenum and low copper is induced by molybdenum the synthesis of xanthine oxidase, its activity increases and the formation of uric acid increases. With an increase in the content of uric acid in the body, it induces the synthesis of urate oxidase, an enzyme that causes the degradation of uric acid. The relationships between the substances involved in the considered forms of purine metabolism are very complex. With an increase in the amount of copper in the diet and a gradual decrease in the level of molybdenum, interesting adaptive changes in xanthine oxidase occur. With a deficiency of molybdenum and an increased content of copper, its activity is still preserved. Our studies have shown that milk xanthine oxidase under these conditions can be enriched with copper by 3.5-5.5 times, losing molybdenum. The synthesis of urate oxidase in these cases is induced not only by uric acid, but also by copper, the content of which is increased.

In these experiments, when the body is exposed to various ratios of copper and molybdenum, a high optimum of xanthine oxidase activity can be achieved, which does not correspond to the physiological optimum observed with a ratio of copper and molybdenum in the diet of 1:4.

This previously unknown form of molecular adaptation of processes in the rat organism is obviously a phenotypic manifestation of the gene function of the enzyme.

In ecological studies, therefore, it is possible to approach the analysis of the process of evolution of organisms - variability, adaptability, the formation of new taxonomic units, natural selection and their genetic foundations. For such a study of questions of evolution, the geochemical ecology of organisms and their populations under extreme environmental conditions, with an excess or insufficient content of microelements in the biosphere, opens the way.

IONIC AND GAS METABOLOM OF LIQUID MEDIA OF THE ORGANISM

The human body, on average, consists of 60% of body weight water. Water fills all the components of cells and extracellular space and is the medium in which biochemical reactions, the transfer of substances and chemical energy take place. Biochemical reactions take place in the aquatic environment of the body at a constant temperature.

Water is a medium in which various substances that make up the body are dissolved, or dispersed. Water contains the main macrocomponents of the body - proteins, carbohydrates, lipids, as well as microelements, nucleic acids and other microcomponents.

Water is the basis of fluids circulating in the body, it also takes part in metabolic processes.

Obviously, knowledge of the properties of solutions is necessary for understanding biochemical transformations in the human body.

Solutions are of great importance both in everyday life and in medicine. According to modern concepts, life arose in the ocean, which was an aqueous solution of inorganic and organic substances. In the course of evolution, living organisms developed and changed. Many of them left the ocean and moved to land. However, animals and plants, having left the sea cradle, retained in their bodies aqueous solutions containing various inorganic ions and organic substances. The solutions are blood plasma, cerebrospinal fluid and lymph. Medicinal substances are effective only in a dissolved state or must go into a dissolved state in the body.

METABOLISM AND METABOLIC PATHWAYS

Metabolism(from Greek. metabole- "movement, change, transformation") - a set of biochemical transformations of substances entering the body, and the interconversion of substances that make up the body.

Transformations (metabolism) of substances in metabolic processes are carried out through chains of successive reactions. These chains of successive reactions are called metabolic pathways(MP).

The nature of metabolism in tissues is largely determined by nutrition.

In humans and other mammals, products that are absorbed after the digestion of proteins, fats and carbohydrates contained in food undergo metabolic transformations.

In ruminants (and to a lesser extent in other herbivores), cellulose is digested by symbiotic microorganisms with the formation of lower homologues of organic acids (acetic, propionic, butyric); tissue metabolism in these animals is adapted to the utilization of lower fatty acids as the main substrate.

In an experimental study of the metabolic pathway, first, the reacting components are identified, the stoichiometry and the mechanism for each of the successive stages of the process are clarified. The final stage of such a study is the reproduction of enzymatic reactions in vitro. Secondly, genetic, allosteric and hormonal mechanisms are identified that regulate the rate of this metabolic process.

Metabolic pathways in the whole organism are studied either by the method of determining the substances introduced into the body and excreted from it (in normal conditions, as well as under conditions of stress and pathology), or by the method of perfusion (washing) of individual organs, or by the method of surviving tissue sections. The method based on the study of the resulting mutant organisms with genetic defects, as well as the method of labeled atoms, is considered very promising.

Table 2.1. The relationship of general catabolism (splitting) and anabolism (synthesis)

Metabolism includes catabolism and anabolism.

Catabolism- phase of decay, enzymatic splitting of complex molecules into simpler ones, metabolic path from complex to simple.

Anabolism- synthesis of complex molecules from small ones, metabolic pathway from simple to complex.

In turn, each of these processes (catabolism and anabolism) consists of two simultaneously occurring interconnected processes:

Intermediate metabolism - a sequence of enzymatic reactions of decomposition or synthesis, the intermediate products of which are called "metabolites";

Energy conjugation - energy transformations in metabolic reactions, as a result of which energy is either stored in high-energy compounds (ATP, NADPH), or consumed during the breakdown of these compounds (Table 2.1).

The processes of general catabolism can be divided into three main stages (Fig. 2.1).

Rice. 2.1. Three main stages of catabolism

The first two stages of catabolism are the breakdown of proteins, polysaccharides and lipids to pyruvate and acetyl-coenzyme-A (acetyl-CoA). The third stage is the citric acid cycle, the main process that provides the body with energy and various metabolites.

The processes of anabolism also include three stages. The starting materials, or building blocks, are compounds supplied by catabolic processes for anabolism.

Catabolic and anabolic pathways are not the same.

Metabolism of nutrients. The food entering the body, largely consisting of proteins, carbohydrates and fats, must be destructured to such components as amino acids, hexoses, fatty acids, which are directly involved in metabolic processes. The transformation of the starting substances into resorbable substrates occurs in stages as a result of catabolism processes that take place with the participation of various enzymes.