Macroergic communication and connections. What bonds are called macroergic? The role of the ATP molecule in energy metabolism. How many high-energy bonds does the ATP molecule contain?

The source of energy for the human body is the oxidation of chemical organic compounds to less energetically valuable end products. With the help of enzyme systems, energy is extracted from external substrates (nutrients) in reactions of their stepwise oxidation, leading to the release of energy in small portions. External energy sources must be transformed in the cell into a specific form convenient for meeting intracellular energy needs. This form is predominantly a molecule adenosine triphosphate (ATP) , representing a mononucleotide. ATP is a high-energy compound; it contains two energy-rich bonds (high-energy bonds): between the second and third phosphoric acid residues. Macroergic bonds are covalent bonds in chemical compounds of the cell that are hydrolyzed with the release of a significant amount of energy - 30 kJ/mol or more. During the hydrolysis of each of the high-energy bonds in the ATP molecule, about 32 kJ/mol is released. ATP hydrolysis is carried out by special enzymes called ATPases: There are other high-energy compounds in the cell. Most of them, like ATP, contain a high-energy phosphate bond. This group of compounds also includes other nucleoside triphosphates, acyl phosphates, phosphoenolpyruvate, creatine phosphate and other molecules. In addition, in living organisms there are molecules with high-energy thioether bonds, acylthioesters. However, the ATP molecule still plays the largest role in energy cellular processes. This molecule has a number of properties that allow it to occupy such a significant place in cellular metabolism. Firstly, the ATP molecule is thermodynamically unstable, as evidenced by the change in the free energy of ATP hydrolysis DG0 = –31.8 kJ/mol. Secondly, the ATP molecule is chemically highly stable. The rate of non-enzymatic hydrolysis of ATP under normal conditions is very low, which allows energy to be effectively stored, preventing its useless dissipation into heat. Thirdly, the ATP molecule is small, which allows it to enter various intracellular sites through diffusion. Finally, the hydrolysis energy of ATP is intermediate to that of other phosphorylated cellular molecules, allowing ATP to transfer energy from high- to low-energy compounds.

There are two mechanisms for ATP synthesis in the cell: substrate phosphorylation and membrane phosphorylation. Substrate phosphorylation– enzymatic transfer of a phosphate group to ADP molecules with the formation of ATP, which occurs in the cytoplasm. During substrate phosphorylation, as a result of certain redox reactions, energy-rich unstable molecules are formed, the phosphate group of which is transferred to ADP with the help of appropriate enzymes to form ATP. Substrate phosphorylation reactions occur in the cytoplasm and are catalyzed by soluble enzymes. Membrane phosphorylation– synthesis of the ATP molecule using the energy of the transmembrane gradient of hydrogen ions, occurring on the mitochondrial membrane. Membrane phosphorylation occurs on the mitochondrial membrane, in which a certain chain of hydrogen and electron transport molecules is localized. Hydrogen atoms and electrons are split off from oxidizing organic molecules and, with the help of special carriers, enter the electron transport chain (respiratory chain), localized on the inner membrane of mitochondria. This chain is a complex of membrane proteins arranged in a strictly defined manner. These proteins are enzymes that catalyze redox reactions. Moving from one respiratory chain carrier protein to another, the electron descends to an increasingly lower energy level. The transfer of electrons along the electron transport chain is associated with the release of protons from the cell into the external environment. As a result, the outer part of the cell membrane acquires a positive charge, and the inner part acquires a negative charge, and charge separation occurs. In addition, a gradient of hydrogen ions is formed on the membrane. Thus, the energy released during electron transfer is initially stored in the form electrochemical transmembrane gradient of hydrogen ions (DmH+) . That is, chemical and electromagnetic energy is converted into electrochemical energy, which can be further used by the cell for the synthesis of ATP. ATP synthesis reaction due to DmH + and is called membrane phosphorylation; membranes on which it is carried out - energy-converting or conjugating . The conversion of the energy released during electron transport into the energy of the phosphate bond of ATP explains chemoosmotic theory of energy coupling (Fig. 8), developed by the English biochemist P. Mitchell. The coupling membrane can be likened to a dam that restrains the pressure of water, just as the membrane restrains the gradient of hydrogen ions. If the dam is opened, the energy from the water can be used to do work or converted into another form of energy, such as electricity, as happens in hydroelectric power plants. Similarly, the cell has a mechanism that allows the energy of the transmembrane gradient of hydrogen ions to be converted into the energy of the chemical bond of ATP. Discharge of the transmembrane gradient of hydrogen ions occurs with the participation of hydrogen ions localized in the same membrane proton ATP synthase complex . The proton energy supplied through this enzymatic complex into the cell from the external environment is used to synthesize the ATP molecule from ADP and a phosphoric acid residue. The ongoing process can be expressed by the equation:

ADP + Fn+ nH+ext à ATP + H2O + nH+ext.

1. What words are missing from the sentence and replaced with letters (a-d)?

“The ATP molecule consists of a nitrogenous base (a), a five-carbon monosaccharide (b) and (c) an acid residue (d).”

The following words are replaced by letters: a – adenine, b – ribose, c – three, d – phosphoric.

2. Compare the structure of ATP and the structure of a nucleotide. Identify similarities and differences.

In fact, ATP is a derivative of the adenyl nucleotide of RNA (adenosine monophosphate, or AMP). The molecules of both substances include the nitrogenous base adenine and the five-carbon sugar ribose. The differences are due to the fact that the adenyl nucleotide of RNA (as in any other nucleotide) contains only one phosphoric acid residue, and there are no high-energy (high-energy) bonds. The ATP molecule contains three phosphoric acid residues, between which there are two high-energy bonds, so ATP can act as a battery and energy carrier.

3. What is the process of ATP hydrolysis? ATP synthesis? What is the biological role of ATP?

During the process of hydrolysis, one phosphoric acid residue is removed from the ATP molecule (dephosphorylation). In this case, the high-energy bond is broken, 40 kJ/mol of energy is released and ATP is converted into ADP (adenosine diphosphoric acid):

ATP + H 2 O → ADP + H 3 PO 4 + 40 kJ

ADP can undergo further hydrolysis (which rarely occurs) with the elimination of another phosphate group and the release of a second “portion” of energy. In this case, ADP is converted into AMP (adenosine monophosphoric acid):

ADP + H 2 O → AMP + H 3 PO 4 + 40 kJ

ATP synthesis occurs as a result of the addition of a phosphoric acid residue to the ADP molecule (phosphorylation). This process occurs mainly in mitochondria and chloroplasts, partly in the hyaloplasm of cells. To form 1 mole of ATP from ADP, at least 40 kJ of energy must be expended:

ADP + H 3 PO 4 + 40 kJ → ATP + H 2 O

ATP is a universal storehouse (battery) and carrier of energy in the cells of living organisms. In almost all biochemical processes occurring in cells that require energy, ATP is used as an energy supplier. Thanks to the energy of ATP, new molecules of proteins, carbohydrates, lipids are synthesized, active transport of substances is carried out, the movement of flagella and cilia occurs, cell division occurs, muscles work, a constant body temperature is maintained in warm-blooded animals, etc.

4. What connections are called macroergic? What functions can substances containing high-energy bonds perform?

Macroergic bonds are those whose rupture releases a large amount of energy (for example, the rupture of each macroergic ATP bond is accompanied by the release of 40 kJ/mol of energy). Substances containing high-energy bonds can serve as batteries, carriers and suppliers of energy for various life processes.

5. The general formula of ATP is C 10 H 16 N 5 O 13 P 3. When 1 mole of ATP is hydrolyzed to ADP, 40 kJ of energy is released. How much energy will be released during the hydrolysis of 1 kg of ATP?

● Calculate the molar mass of ATP:

M (C 10 H 16 N 5 O 13 P 3) = 12 × 10 + 1 × 16 + 14 × 5 + 16 × 13 + 31 × 3 = 507 g/mol.

● When 507 g of ATP (1 mol) is hydrolyzed, 40 kJ of energy is released.

This means that upon hydrolysis of 1000 g of ATP, the following will be released: 1000 g × 40 kJ: 507 g ≈ 78.9 kJ.

Answer: When 1 kg of ATP is hydrolyzed to ADP, about 78.9 kJ of energy will be released.

6. ATP molecules labeled with radioactive phosphorus 32 R at the last (third) phosphoric acid residue were introduced into one cell, and ATP molecules labeled with 32 R at the first (closest to ribose) residue were introduced into the other cell. After 5 minutes, the content of inorganic phosphate ion labeled with 32 R was measured in both cells. Where was it higher and why?

The last (third) phosphoric acid residue is easily cleaved off during the hydrolysis of ATP, and the first (closest to ribose) is not cleaved off even during the two-step hydrolysis of ATP to AMP. Therefore, the content of radioactive inorganic phosphate will be higher in the cell into which ATP, labeled at the last (third) phosphoric acid residue, was introduced.

The source of energy for the human body is the oxidation of chemical organic compounds to less energetically valuable end products. With the help of enzyme systems, energy is extracted from external substrates (nutrients) in reactions of their stepwise oxidation, leading to the release of energy in small portions. External energy sources must be transformed in the cell into a specific form convenient for meeting intracellular energy needs. This form is predominantly a molecule adenosine triphosphate (ATP) , representing a mononucleotide (Fig. 6).

Rice. 6. Structural formula of the adenosine triphosphoric acid (ATP) molecule

ATP is high-energy compound , it contains two bonds rich in energy ( macroergic connections) : between the second and third phosphoric acid residues. Macroergic connections – covalent bonds in chemical compounds of the cell, which are hydrolyzed with the release of a significant amount of energy - 30 kJ/mol or more. During the hydrolysis of each of the high-energy bonds in the ATP molecule, about 32 kJ/mol is released. ATP hydrolysis is carried out by special enzymes called ATPases:

ATP ® ADP + H3PO4; ADP ® AMP + H3PO4

There are others in the cell macroergic connections. Most of them, like ATP, contain a high-energy phosphate bond. This group of compounds also includes other nucleoside triphosphates, acyl phosphates, phosphoenolpyruvate, creatine phosphate and other molecules. In addition, living organisms contain molecules with high-energy thioether bonds, acylthioesters (Fig. 7).

However, the ATP molecule still plays the greatest role in energy cellular processes. This molecule has a number of properties that allow it to occupy such a significant place in cellular metabolism. Firstly, the ATP molecule is thermodynamically unstable, as evidenced by the change in the free energy of ATP hydrolysis DG0 = –31.8 kJ/mol. Secondly, the ATP molecule is chemically highly stable. The rate of non-enzymatic hydrolysis of ATP under normal conditions is very low, which allows energy to be effectively stored, preventing its useless dissipation into heat. Thirdly, the ATP molecule is small, which allows it to enter various intracellular sites by diffusion. Finally, the hydrolysis energy of ATP is intermediate to that of other phosphorylated cellular molecules, allowing ATP to transfer energy from high- to low-energy compounds.

Rice. 7. Types of compounds characterized by high hydrolysis energy

There are two mechanisms for ATP synthesis in the cell: substrate phosphorylation and membrane phosphorylation. Substrate phosphorylation– enzymatic transfer of a phosphate group to ADP molecules with the formation of ATP, which occurs in the cytoplasm. During substrate phosphorylation, as a result of certain redox reactions, energy-rich unstable molecules are formed, the phosphate group of which is transferred to ADP with the help of appropriate enzymes to form ATP. Substrate phosphorylation reactions occur in the cytoplasm and are catalyzed by soluble enzymes.

Membrane phosphorylation– synthesis of the ATP molecule using the energy of the transmembrane gradient of hydrogen ions, occurring on the mitochondrial membrane. Membrane phosphorylation occurs on the mitochondrial membrane, in which a certain chain of hydrogen and electron transport molecules is localized. Hydrogen atoms and electrons are split off from oxidizing organic molecules and, with the help of special carriers, enter the electron transport chain (respiratory chain), localized on the inner membrane of mitochondria. This chain is a complex of membrane proteins arranged in a strictly defined manner. These proteins are enzymes that catalyze redox reactions. Moving from one respiratory chain carrier protein to another, the electron descends to an increasingly lower energy level. The transfer of electrons along the electron transport chain is associated with the release of protons from the cell into the external environment. As a result, the outer part of the cell membrane acquires a positive charge, and the inner part acquires a negative charge, and charge separation occurs. In addition, a gradient of hydrogen ions is formed on the membrane. Thus, the energy released during electron transfer is initially stored in the form electrochemical transmembrane gradient of hydrogen ions ( D mH+) . That is, chemical and electromagnetic energy is converted into electrochemical energy, which can be further used by the cell for the synthesis of ATP. ATP synthesis reaction due to DmH + and is called membrane phosphorylation; membranes on which it is carried out - energy-converting or conjugating . The conversion of the energy released during electron transport into the energy of the phosphate bond of ATP explains chemoosmotic theory of energy coupling (Fig. 8), developed by the English biochemist P. Mitchell. The coupling membrane can be likened to a dam that restrains the pressure of water, just as the membrane restrains the gradient of hydrogen ions. If the dam is opened, the energy from the water can be used to do work or converted into another form of energy, such as electricity, as happens in hydroelectric power plants. Similarly, the cell has a mechanism that allows the energy of the transmembrane gradient of hydrogen ions to be converted into the energy of the chemical bond of ATP. Discharge of the transmembrane gradient of hydrogen ions occurs with the participation of hydrogen ions localized in the same membrane proton ATP synthase complex . The proton energy supplied through this enzymatic complex into the cell from the external environment is used to synthesize the ATP molecule from ADP and a phosphoric acid residue. The ongoing process can be expressed by the equation:

ADP + Fn+ nH+ext à ATP + H2O + nH+ext.

The ATP synthase enzymatic complex serves as a mechanism that ensures the interconversion of two forms of cellular energy: DmH + « ATP.

Rice. 8. Scheme of operation of the electron transport chain and ATP synthase complex AN 2 and IN– electron donor and acceptor, respectively; 1 , 2 , 3 – components of the electron transport chain

The starting carrier of the mitochondrial respiratory chain is NAD(P)H dehydrogenase, which is of flavin nature. This enzyme accepts protons and electrons from primary dehydrogenase, an enzyme that removes hydrogen atoms directly from the substrate. From NAD(P)H dehydrogenase, electrons are transferred to a quinone carrier, ubiquinone (coenzyme Q), and then to cytochromes (Fig. 9). There are 5 different cytochromes in mitochondria (b, c, c1, a, a3). Cytochromes are hemoproteins, their non-protein part is heme and contains a metal cation. Cytochromes are colored red-brown. Cytochromes of classes b and c contain an iron cation, and cytochromes of class a contain a copper cation.

Rice. 9. Respiratory electron transport chain of mitochondria

The final cytochrome (a+a3) transfers electrons to oxygen, i.e. is a cytochrome oxidase. 4 electrons are transferred to oxygen and water is formed. During the synthesis of an ATP molecule, at least two protons pass through the ATP synthase complex. The number of ATP molecules synthesized depends on the number of chain sections in which protons are released into the external environment. In the mitochondrion there are 3 sections of the oxidative chain where protons are excreted and Dmn+ is generated: at the beginning of the chain at NAD(P)H dehydogenase, at ubiquinone and at cytochrome oxidase (Fig. 9). In mitochondria, during the oxidation of one NAD(P)H molecule, two electrons are transferred along the chain, and 6H+ is released into the external environment and, accordingly, three ATP molecules are synthesized.

Practical lesson No. 15.

Assignment for lesson No. 15.

Topic: ENERGY EXCHANGE.

Relevance of the topic.

Biological oxidation is a set of enzymatic processes occurring in each cell, as a result of which molecules of carbohydrates, fats and amino acids are ultimately broken down into carbon dioxide and water, and the released energy is stored by the cell in the form of adenosine triphosphoric acid (ATP) and then used in the life of the body ( biosynthesis of molecules, cell division process, muscle contraction, active transport, heat production, etc.). The doctor should be aware of the existence of hypoenergetic states, in which ATP synthesis is reduced. In this case, all vital processes that occur using energy stored in the form of macroergic bonds of ATP suffer. The most common cause of hypoenergetic conditions is tissue hypoxia, associated with a decrease in oxygen concentration in the air, disruption of the cardiovascular and respiratory systems, and anemia of various origins. In addition, hypoenergetic states can be caused by hypovitaminosis associated with a violation of the structural and functional state of enzyme systems involved in the process of biological oxidation, as well as starvation, which leads to the absence of substrates for tissue respiration. In addition, in the process of biological oxidation, reactive oxygen species are formed, which trigger the processes peroxidation lipids of biological membranes. It is necessary to know the body's defense mechanisms against these forms (enzymes, drugs that have a membrane-stabilizing effect - antioxidants).

Educational and educational goals:

The general goal of the lesson: to instill knowledge about the course of biological oxidation, which results in the formation of up to 70-8% of energy in the form of ATP, as well as the formation of reactive oxygen species and their damaging effects on the body.

Private goals: to be able to determine peroxidase in horseradish and potatoes; muscle succinate dehydrogenase activity.

1. Incoming knowledge control:

1.1. Tests.

1.2. Oral survey.

2. Main questions of the topic:

2.1. The concept of metabolism. Anabolic and catabolic processes and their relationship.

2.2. Macroergic compounds. ATP is a universal battery and source of energy in the body. ATP-ADP cycle. Energy charge of the cell.

2.3. Metabolic stages. Biological oxidation (tissue respiration). Features of biological oxidation.

2.4. Primary acceptors of hydrogen protons and electrons.

2.5. Organization of the respiratory chain. Carriers in the respiratory chain (CRE).

2.6. Oxidative phosphorylation of ADP. The mechanism of coupling of oxidation and phosphorylation. Oxidative phosphorylation ratio (P/O).

2.7. Respiratory control. Separation of respiration (oxidation) and phosphorylation (free oxidation).

2.8. Formation of toxic forms of oxygen in CPE and neutralization of hydrogen peroxide by the enzyme peroxidase.

Laboratory and practical work.

3.1. Method for determining peroxidase in horseradish.

3.2. Method for determining peroxidase in potatoes.

3.3. Determination of muscle succinate dehydrogenase activity and competitive inhibition of its activity.

Output control.

4.1. Tests.

4.2. Situational tasks.

5. Literature:

5.1. Lecture materials.

5.2. Nikolaev A.Ya. Biological chemistry.-M.: Higher School, 1989., pp. 199-212, 223-228.

5.3. Berezov T.T., Korovkin B.F. Biological chemistry. - M.: Medicine, 1990.P.224-225.

5.4. Kushmanova O.D., Ivchenko G.M. Guide to practical classes in biochemistry. - M.: Medicine, 1983, work. 38.

2. Main questions of the topic.

2.1. The concept of metabolism. Anabolic and catabolic processes and their relationship.

Living organisms are in constant and inextricable connection with the environment.

This connection is carried out in the process of metabolism.

Metabolism (metabolism) – the totality of all reactions in the body.

Intermediate metabolism (intracellular metabolism) - includes 2 types of reactions: catabolism and anabolism.

Catabolism– the process of breaking down organic substances into final products (CO 2 , H 2 O and urea). This process includes metabolites formed both during digestion and during the breakdown of the structural and functional components of cells.

The processes of catabolism in the cells of the body are accompanied by the consumption of oxygen, which is necessary for oxidation reactions. As a result of catabolic reactions, energy is released (exergonic reactions), which is necessary for the body to function.

Anabolism- synthesis of complex substances from simple ones. Anabolic processes use energy released during catabolism (endergonic reactions).

Sources of energy for the body are proteins, fats and carbohydrates. The energy contained in the chemical bonds of these compounds was transformed from solar energy during the process of photosynthesis.

Macroergic compounds. ATP is a universal battery and source of energy in the body. ATP-ADP cycle. Energy charge of the cell.

ATP– is a high-energy compound containing high-energy bonds; hydrolysis of the terminal phosphate bond releases about 20 kJ/mol of energy.

High-energy compounds include GTP, CTP, UTP, creatine phosphate, carbamoyl phosphate, etc. They are used in the body for the synthesis of ATP. For example, GTP + ADP à GDP + ATP

This process is called substrate phosphorylation– exorgonic reactions. In turn, all these high-energy compounds are formed by using the free energy of the terminal phosphate group of ATP. Finally, ATP energy is used to perform various types of work in the body:

Mechanical (muscle contraction);

Electrical (conducting nerve impulses);

Chemical (synthesis of substances);

Osmotic (active transport of substances across the membrane) – endergonic reactions.

Thus, ATP is the main, directly used energy donor in the body. ATP occupies a central position between endergonic and exergonic reactions.

The human body produces an amount of ATP equal to body weight, and every 24 hours all this energy is destroyed. 1 molecule of ATP “lives” in a cell for about a minute.

The use of ATP as an energy source is possible only under the condition of continuous synthesis of ATP from ADP due to the energy of oxidation of organic compounds. The ATP-ADP cycle is the primary mechanism for energy exchange in biological systems, and ATP is the universal “energy currency.”

Each cell has an electrical charge equal to

[ATP] + ½[ADP]

[ATP] + [ADP] + [AMP]

If the cell charge is 0.8-0.9, then the entire adenyl fund in the cell is presented in the form of ATP (the cell is saturated with energy and the process of ATP synthesis does not occur).

As energy is used, ATP is converted into ADP, the cell charge becomes equal to 0, and ATP synthesis automatically begins.

I Macroergic compounds (Greek: makros big + ergon work, action; synonym: high-energy compounds, high-energy compounds)

a group of natural substances whose molecules contain energy-rich, or high-energy, bonds; present in all living cells and are involved in the accumulation and transformation of energy. Breaking of high-energy bonds in M.s. molecules. accompanied by the release of energy used for the biosynthesis and transport of substances, muscle contraction, digestion and other vital processes of the body.

All known M.s. contain phosphoryl (-PO 3 H 2) or acyl

groups and can be described by the formula X-Y, where X is a nitrogen, oxygen, sulfur or carbon atom, and Y is a phosphorus or carbon atom. Reactivity M.s. is associated with an increased affinity for the electron of the Y atom, which determines the high free energy of hydrolysis M.s., amounting to 6-14 kcal/mol.

An important group of compounds, which includes M.s., are adenosine phosphoric, or adenylic, acids - nucleosides containing adenine, ribose and phosphoric acid residues (see. rice .).

The most significant of them is adenosine triphosphate (adenosine triphosphate, ATP).

ATP is an adenosine phosphoric acid containing 3 phosphoric acid residues (or phosphate residues), serves as a universal carrier and the main accumulator of chemical energy in living cells, a coenzyme of many enzymes (see Coenzymes) . ATP is not the only biologically active compound containing pyrophosphate bonds. Some phosphorylated compounds do not differ from ATP in the amount of energy contained in such bonds. However, diphosphates of such compounds cannot replace adenosine diphosphoric acid in those processes that lead to the synthesis of ATP, and their triphosphates cannot replace ATP in subsequent energy metabolism processes in which ATP is used as a donor of energy necessary for biosynthetic reactions. It is possible that such a high degree of specificity reflects not so much the uniqueness of ATP, but rather the unique features of biochemical processes adapted exclusively to ATP.

In some biosynthetic reactions, the direct source of energy is not ATP, but some other triphosphonucleotides. However, they cannot be considered a primary source of energy, since they themselves are formed as a result of the transfer of a phosphate or pyrophosphate group from ATP. This is also true for another type of substance adapted for storing energy - creatine phosphate (see Creatinine) . Two pyrophosphate bonds in the ATP molecule are macroergic: between α- and β- and between β- and γ-phosphate residues. Hydrolysis of the terminal pyrophosphate bond releases 8,4 kcal/mol(at pH 7.0, temperature 37°, excess Mg 2+ ions and ATP concentration equal to 1 M). All processes in the body that are accompanied by the accumulation of energy ultimately lead to the formation of ATP, which acts as a link between processes involving energy consumption and processes accompanied by the release and accumulation of energy.

The cleavage of phosphate residues from ATP molecules occurs with the participation of adenosine triphosphatases (ATPases) - enzymes of the class of hydrolases, widespread in the cells of all organisms and ensuring the use of ATP energy for various vital processes. A group of transport ATPases actively transports ions, amino acids, nucleotides, sugars and other substances through biological membranes, creating and maintaining ion concentration gradients (ion gradients) on both sides of biological membranes. Active transport of ions, provided by the energy of ATP hydrolysis, underlies the bioenergetics (Bioenergetics) of the cell, the processes of cellular excitation, entry into the cell and removal of substances from the cell and the body. The most important transport ATPases that ensure the transfer of ions during ATP hydrolysis include H + - ATPase of membranes of mitochondria, chloroplasts and bacterial cells, Ca 2+ - ATPase of intracellular membranes of muscle cells and erythrocytes, as well as Na +, K + ATPase contained in almost all plasma membranes. As a result of the transport of ions carried out by these enzymes against their concentration gradient on the membrane, an electrical potential difference is generated. Impaired functioning of transport ATPases (for example, switching off ATPases under hypoxic conditions in the absence of ATP) leads to the development of many pathological conditions. There are known drugs (for example, cardiac glycosides) that regulate the activity of these enzymes.

The cleavage of ATP can be accompanied not only by the transfer of a phosphoryl group to an acceptor molecule, as occurs in reactions catalyzed by kinases (Kinases) , but also by the transfer of a pyrophosphate group (for example, during the synthesis of purines), an adenylic acid residue (when activating amino acids during protein synthesis) or adenosine (biosynthesis of S-adenosylmethionine).

ATP is formed from adenosine diphosphoric acid (ADP) as a result of oxidative phosphorylation during electron transfer in the mitochondrial electron transport chain (see Tissue respiration , Metabolism and energy) or as a result of phosphorylation at the substrate level (see Glycolysis) . The ATP content in the cell is directly related to the content of other adenosine phosphoric acids - ADP and adenylic acid (AMP), which form the cell's adenyl nucleotide system. The total concentration of adenyl nucleotides in the cell is 2-15 mm, which is approximately 87% of the total fund of free nucleotides. A significant role in maintaining the balance between adenosine phosphoric acids is played by a reversible and practically equilibrium reaction catalyzed by the enzyme adenylate kinase (muscle tissue adenylate kinase is called myokinase): ATP + AMP = 2 ADP.

An important high-energy compound involved in the resynthesis of ATP in muscle tissue is creatine phosphate, a phosphorylated derivative of creatine, or β-methylguanidinacetic acid, contained in the skeletal muscles of all vertebrates (see Creatinine) . The reversible enzymatic interaction of creatine with ATP: creatine + ATP = creatine phosphate + ADP, catalyzed by creatine kinase (creatine phosphokinase), plays a significant role in the accumulation of energy necessary for muscle contraction.

Along with ATP, high-energy compounds also include other nucleoside triphosphoric acids: guanosine triphosphate (GTP), uridine triphosphate (UTP), inosine triphosphate (ITP) and thymidine triphosphate (TTP), which play the role of energy suppliers in various biosynthetic processes and interconversions of carbohydrates, lipids, as well as the corresponding nucleoside diphosphorus acids, pyrophosphoric and polyphosphoric acids (see Phosphorus) , phosphoenolpyruvic and 1,3-diphosphoglyceric acids, acetyl and succinyl coenzyme A, aminoacyl derivatives of adenylic and ribonucleic acids, etc.

Bibliography: Broda E. Evolution of bioenergetic processes, trans. from English, M., 1978: Pevzner L. Fundamentals of bioenergy, trans. from English, M., 1977; Racker E. Bioenergetic mechanisms, trans. from English, M., 1979; Skulachev V.P. Transformation of energy in biomembranes, M., 1972.