ATP physiology. ATP molecule - what is it and what is its role in the body
Continuation. See No. 11, 12, 13, 14, 15, 16/2005
Biology lessons in science classes
Advanced Planning, Grade 10
Lesson 19
Equipment: tables on general biology, a diagram of the structure of the ATP molecule, a diagram of the relationship between plastic and energy exchanges.
I. Knowledge Test
Conducting a biological dictation "Organic compounds of living matter"
The teacher reads the theses under the numbers, the students write down in the notebook the numbers of those theses that are suitable in content to their version.
Option 1 - proteins.
Option 2 - carbohydrates.
Option 3 - lipids.
Option 4 - nucleic acids.
1. In its pure form, they consist only of C, H, O atoms.
2. In addition to C, H, O atoms, they contain N and usually S atoms.
3. In addition to the C, H, O atoms, they contain N and P atoms.
4. They have a relatively small molecular weight.
5. The molecular weight can be from thousands to several tens and hundreds of thousands of daltons.
6. The largest organic compounds with a molecular weight of up to several tens and hundreds of millions of daltons.
7. They have different molecular weights - from very small to very high, depending on whether the substance is a monomer or a polymer.
8. Consist of monosaccharides.
9. Consist of amino acids.
10. Consist of nucleotides.
11. They are esters of higher fatty acids.
12. Basic structural unit: "nitrogenous base - pentose - phosphoric acid residue".
13. Basic structural unit: "amino acids".
14. Basic structural unit: "monosaccharide".
15. Basic structural unit: "glycerol-fatty acid".
16. Polymer molecules are built from the same monomers.
17. Polymer molecules are built from similar, but not exactly identical, monomers.
18. Are not polymers.
19. They perform almost exclusively energy, construction and storage functions, in some cases - protective.
20. In addition to energy and construction, they perform catalytic, signal, transport, motor and protective functions;
21. They store and transfer the hereditary properties of the cell and the body.
Option 1 – 2; 5; 9; 13; 17; 20.
Option 2 – 1; 7; 8; 14; 16; 19.
Option 3 – 1; 4; 11; 15; 18; 19.
Option 4– 3; 6; 10; 12; 17; 21.
II. Learning new material
1. The structure of adenosine triphosphoric acid
In addition to proteins, nucleic acids, fats and carbohydrates, a large number of other organic compounds are synthesized in living matter. Among them, an important role in the bioenergetics of the cell is played by adenosine triphosphate (ATP). ATP is found in all plant and animal cells. In cells, adenosine triphosphoric acid is most often present in the form of salts called adenosine triphosphates. The amount of ATP fluctuates and averages 0.04% (on average there are about 1 billion ATP molecules in a cell). The largest amount of ATP is found in skeletal muscles (0.2–0.5%).
The ATP molecule consists of a nitrogenous base - adenine, pentose - ribose and three residues of phosphoric acid, i.e. ATP is a special adenyl nucleotide. Unlike other nucleotides, ATP contains not one, but three phosphoric acid residues. ATP refers to macroergic substances - substances containing a large amount of energy in their bonds.
Spatial model (A) and structural formula (B) of the ATP molecule
From the composition of ATP under the action of ATPase enzymes, a residue of phosphoric acid is cleaved off. ATP has a strong tendency to detach its terminal phosphate group:
ATP 4– + H 2 O ––> ADP 3– + 30.5 kJ + Fn,
because this leads to the disappearance of the energetically unfavorable electrostatic repulsion between neighboring negative charges. The resulting phosphate is stabilized by the formation of energetically favorable hydrogen bonds with water. The charge distribution in the ADP + Fn system becomes more stable than in ATP. As a result of this reaction, 30.5 kJ are released (when a conventional covalent bond is broken, 12 kJ is released).
In order to emphasize the high energy "cost" of the phosphorus-oxygen bond in ATP, it is customary to denote it with the sign ~ and call it a macroenergetic bond. When one molecule of phosphoric acid is cleaved off, ATP is converted to ADP (adenosine diphosphoric acid), and if two molecules of phosphoric acid are cleaved off, then ATP is converted to AMP (adenosine monophosphoric acid). The cleavage of the third phosphate is accompanied by the release of only 13.8 kJ, so that there are only two macroergic bonds in the ATP molecule.
2. Formation of ATP in the cell
The supply of ATP in the cell is small. For example, in a muscle, ATP reserves are enough for 20–30 contractions. But a muscle can work for hours and produce thousands of contractions. Therefore, along with the breakdown of ATP to ADP, reverse synthesis must continuously occur in the cell. There are several pathways for the synthesis of ATP in cells. Let's get to know them.
1. anaerobic phosphorylation. Phosphorylation is the process of ATP synthesis from ADP and low molecular weight phosphate (Pn). In this case, we are talking about oxygen-free processes of oxidation of organic substances (for example, glycolysis is the process of oxygen-free oxidation of glucose to pyruvic acid). Approximately 40% of the energy released during these processes (about 200 kJ / mol of glucose) is spent on ATP synthesis, and the rest is dissipated in the form of heat:
C 6 H 12 O 6 + 2ADP + 2Fn -–> 2C 3 H 4 O 3 + 2ATP + 4H.
2. Oxidative phosphorylation- this is the process of ATP synthesis due to the energy of oxidation of organic substances with oxygen. This process was discovered in the early 1930s. 20th century V.A. Engelhardt. Oxygen processes of oxidation of organic substances proceed in mitochondria. Approximately 55% of the energy released in this case (about 2600 kJ / mol of glucose) is converted into the energy of chemical bonds of ATP, and 45% is dissipated in the form of heat.
Oxidative phosphorylation is much more efficient than anaerobic syntheses: if only 2 ATP molecules are synthesized during glycolysis during the breakdown of a glucose molecule, then 36 ATP molecules are formed during oxidative phosphorylation.
3. Photophosphorylation- the process of ATP synthesis due to the energy of sunlight. This pathway of ATP synthesis is characteristic only for cells capable of photosynthesis (green plants, cyanobacteria). The energy of sunlight quanta is used by photosynthetics in the light phase of photosynthesis for the synthesis of ATP.
3. Biological significance of ATP
ATP is at the center of metabolic processes in the cell, being the link between the reactions of biological synthesis and decay. The role of ATP in the cell can be compared with the role of a battery, since during the hydrolysis of ATP, the energy necessary for various life processes ("discharge") is released, and in the process of phosphorylation ("charging"), ATP again accumulates energy in itself.
Due to the energy released during ATP hydrolysis, almost all vital processes in the cell and body occur: transmission of nerve impulses, biosynthesis of substances, muscle contractions, transport of substances, etc.
III. Consolidation of knowledge
Solving biological problems
Task 1. When running fast, we often breathe, there is increased sweating. Explain these phenomena.
Task 2. Why do freezing people start stomping and jumping in the cold?
Task 3. In the well-known work by I. Ilf and E. Petrov "The Twelve Chairs" among many useful tips you can find the following: "Breathe deeply, you are excited." Try to justify this advice from the point of view of the energy processes occurring in the body.
IV. Homework
Start preparing for the test and test (dictate test questions - see lesson 21).
Lesson 20
Equipment: tables on general biology.
I. Generalization of the knowledge of the section
Work of students with questions (individually) with subsequent verification and discussion
1. Give examples of organic compounds that include carbon, sulfur, phosphorus, nitrogen, iron, manganese.
2. How can a living cell be distinguished from a dead one by ionic composition?
3. What substances are in the cell in an undissolved form? What organs and tissues do they include?
4. Give examples of macronutrients included in the active centers of enzymes.
5. What hormones contain trace elements?
6. What is the role of halogens in the human body?
7. How are proteins different from artificial polymers?
8. What is the difference between peptides and proteins?
9. What is the name of the protein that is part of hemoglobin? How many subunits does it consist of?
10. What is ribonuclease? How many amino acids are in it? When was it artificially synthesized?
11. Why is the rate of chemical reactions without enzymes low?
12. What substances are transported by proteins through the cell membrane?
13. How do antibodies differ from antigens? Do vaccines contain antibodies?
14. What substances break down proteins in the body? How much energy is released in this case? Where and how is ammonia neutralized?
15. Give an example of peptide hormones: how do they participate in the regulation of cellular metabolism?
16. What is the structure of sugar with which we drink tea? What other three synonyms for this substance do you know?
17. Why is fat in milk not collected on the surface, but is in suspension?
18. What is the mass of DNA in the nucleus of somatic and germ cells?
19. How much ATP is used by a person per day?
20. What proteins do people make clothes from?
Primary structure of pancreatic ribonuclease (124 amino acids)
II. Homework.
Continue preparation for the test and test in the section "Chemical organization of life."
Lesson 21
I. Conducting an oral test on questions
1. Elementary composition of the cell.
2. Characteristics of organogenic elements.
3. The structure of the water molecule. The hydrogen bond and its significance in the "chemistry" of life.
4. Properties and biological functions of water.
5. Hydrophilic and hydrophobic substances.
6. Cations and their biological significance.
7. Anions and their biological significance.
8. Polymers. biological polymers. Differences between periodic and non-periodic polymers.
9. Properties of lipids, their biological functions.
10. Groups of carbohydrates distinguished by structural features.
11. Biological functions of carbohydrates.
12. Elementary composition of proteins. Amino acids. The formation of peptides.
13. Primary, secondary, tertiary and quaternary structures of proteins.
14. Biological function of proteins.
15. Differences between enzymes and non-biological catalysts.
16. The structure of enzymes. Coenzymes.
17. The mechanism of action of enzymes.
18. Nucleic acids. Nucleotides and their structure. The formation of polynucleotides.
19. Rules of E.Chargaff. The principle of complementarity.
20. Formation of a double-stranded DNA molecule and its spiralization.
21. Classes of cellular RNA and their functions.
22. Differences between DNA and RNA.
23. DNA replication. Transcription.
24. Structure and biological role of ATP.
25. The formation of ATP in the cell.
II. Homework
Continue preparation for the test in the section "Chemical organization of life."
Lesson 22
I. Conducting a written test
Option 1
1. There are three types of amino acids - A, B, C. How many variants of polypeptide chains consisting of five amino acids can be built. Specify these options. Will these polypeptides have the same properties? Why?
2. All living things mainly consist of carbon compounds, and silicon, the analogue of carbon, the content of which in the earth's crust is 300 times more than carbon, is found only in very few organisms. Explain this fact in terms of the structure and properties of the atoms of these elements.
3. ATP molecules labeled with radioactive 32P at the last, third residue of phosphoric acid were introduced into one cell, and ATP molecules labeled with 32P at the first residue closest to ribose were introduced into another cell. After 5 minutes, the content of inorganic phosphate ion labeled with 32P was measured in both cells. Where will it be significantly higher?
4. Studies have shown that 34% of the total number of nucleotides of this mRNA is guanine, 18% is uracil, 28% is cytosine, and 20% is adenine. Determine the percentage composition of the nitrogenous bases of double-stranded DNA, of which the specified mRNA is a mold.
Option 2
1. Fats constitute the "first reserve" in energy metabolism and are used when the reserve of carbohydrates is exhausted. However, in skeletal muscles, in the presence of glucose and fatty acids, the latter are used to a greater extent. Proteins as a source of energy are always used only as a last resort, when the body is starving. Explain these facts.
2. Ions of heavy metals (mercury, lead, etc.) and arsenic are easily bound by sulfide groups of proteins. Knowing the properties of the sulfides of these metals, explain what happens to the protein when combined with these metals. Why are heavy metals poisonous to the body?
3. In the oxidation reaction of substance A into substance B, 60 kJ of energy is released. How many ATP molecules can be maximally synthesized in this reaction? How will the rest of the energy be used?
4. Studies have shown that 27% of the total number of nucleotides of this mRNA is guanine, 15% is uracil, 18% is cytosine, and 40% is adenine. Determine the percentage composition of the nitrogenous bases of double-stranded DNA, of which the specified mRNA is a mold.
To be continued
19. Functions of cell mitochondria. ATP and its role in the cell.
The main source of energy for the cell are nutrients: carbohydrates, fats and proteins, which are oxidized with the help of oxygen. Almost all carbohydrates, before reaching the cells of the body, are converted into glucose due to the work of the gastrointestinal tract and liver. Along with carbohydrates, proteins are also broken down - to amino acids and lipids - to fatty acids. In the cell, nutrients are oxidized under the influence of oxygen and with the participation of enzymes that control the reactions of energy release and its utilization. Almost all oxidative reactions occur in the mitochondria, and the released energy is stored in the form of a macroergic compound - ATP. In the future, it is ATP, and not nutrients, that is used to provide energy for intracellular metabolic processes.
The ATP molecule contains: (1) the nitrogenous base adenine; (2) pentose carbohydrate ribose, (3) three phosphoric acid residues. The last two phosphates are connected to each other and to the rest of the molecule by macroergic phosphate bonds, indicated by the symbol ~ in the ATP formula. Subject to the physical and chemical conditions characteristic of the body, the energy of each such bond is 12,000 calories per 1 mol of ATP, which is many times higher than the energy of an ordinary chemical bond, which is why phosphate bonds are called macroergic. Moreover, these bonds are easily destroyed, providing intracellular processes with energy as soon as the need arises.
When energy is released, ATP donates a phosphate group and turns into adenosine diphosphate. The released energy is used for almost all cellular processes, for example, in biosynthesis reactions and during muscle contraction.
Replenishment of ATP reserves occurs by recombining ADP with the rest of phosphoric acid due to the energy of nutrients. This process is repeated over and over again. ATP is constantly consumed and accumulated, which is why it is called the energy currency of the cell. The turnover time of ATP is only a few minutes.
The role of mitochondria in the chemical reactions of ATP formation. When glucose enters the cell, under the action of cytoplasmic enzymes it turns into pyruvic acid (this process is called glycolysis). The energy released in this process is used to convert a small amount of ADP to ATP, less than 5% of the total energy reserves.
ATP synthesis is 95% carried out in mitochondria. Pyruvic acid, fatty acids and amino acids, formed respectively from carbohydrates, fats and proteins, are eventually converted in the mitochondrial matrix into a compound called acetyl-CoA. This compound, in turn, enters into a series of enzymatic reactions, collectively known as the tricarboxylic acid cycle or the Krebs cycle, to give up its energy. In the tricarboxylic acid cycle, acetyl-CoA is broken down into hydrogen atoms and carbon dioxide molecules. Carbon dioxide is removed from the mitochondria, then from the cell by diffusion and excreted from the body through the lungs.
Hydrogen atoms are chemically very active and therefore immediately react with oxygen diffusing into the mitochondria. The large amount of energy released in this reaction is used to convert many ADP molecules into ATP. These reactions are quite complex and require the participation of a huge number of enzymes that make up the mitochondrial cristae. At the initial stage, an electron is split off from the hydrogen atom, and the atom turns into a hydrogen ion. The process ends with the addition of hydrogen ions to oxygen. As a result of this reaction, water and a large amount of energy are formed that are necessary for the operation of ATP synthetase, a large globular protein that acts as tubercles on the surface of mitochondrial cristae. Under the action of this enzyme, which uses the energy of hydrogen ions, ADP is converted into ATP. New ATP molecules are sent from the mitochondria to all parts of the cell, including the nucleus, where the energy of this compound is used to provide a variety of functions. This process of ATP synthesis is generally called the chemiosmotic mechanism of ATP formation.
Energy of muscle activity
As already mentioned, both phases of muscle activity - contraction and relaxation - proceed with the mandatory use of energy that is released during ATP hydrolysis.
However, the reserves of ATP in muscle cells are insignificant (at rest, the concentration of ATP in muscles is about 5 mmol / l), and they are sufficient for muscle work for 1-2 s. Therefore, to ensure longer muscle activity in the muscles, replenishment of ATP reserves must occur. The formation of ATP in muscle cells directly during physical work is called ATP resynthesis and comes with energy consumption.
Thus, during the functioning of muscles, two processes simultaneously occur in them: ATP hydrolysis, which provides the necessary energy for contraction and relaxation, and ATP resynthesis, which replenishes the loss of this substance. If only the chemical energy of ATP is used to ensure muscle contraction and relaxation, then the chemical energy of a wide variety of compounds is suitable for ATP resynthesis: carbohydrates, fats, amino acids, and creatine phosphate.
The structure and biological role of ATP
Adenosine triphosphate (ATP) is a nucleotide. The ATP (adenosine triphosphoric acid) molecule consists of the nitrogenous base of adenine, the five-carbon sugar of ribose, and three phosphoric acid residues interconnected by a macroergic bond. During its hydrolysis, a large amount of energy is released. ATP is the main macroerg of the cell, an energy accumulator in the form of the energy of high-energy chemical bonds.
Under physiological conditions, that is, under the conditions that exist in a living cell, the splitting of a mole of ATP (506 g) is accompanied by the release of 12 kcal, or 50 kJ of energy.
Ways of ATP formation
Aerobic oxidation (tissue respiration)
Synonyms: oxidative phosphorylation, respiratory phosphorylation, aerobic phosphorylation.
This pathway takes place in the mitochondria.
The tricarboxylic acid cycle was first discovered by the English biochemist G. Krebs (Fig. 4).
The first reaction is catalyzed by the enzyme citrate synthase, in which the acetyl group of acetyl-CoA condenses with oxaloacetate to form citric acid. Apparently, in this reaction, citryl-CoA bound to the enzyme is formed as an intermediate. Then the latter is spontaneously and irreversibly hydrolyzed to form citrate and HS-CoA.
As a result of the second reaction, the resulting citric acid undergoes dehydration with the formation of cis-aconitic acid, which, by attaching a water molecule, passes into isocitric acid (isocitrate). These reversible reactions of hydration-dehydration are catalyzed by the enzyme aconitate hydratase (aconitase). As a result, there is a mutual displacement of H and OH in the citrate molecule.
Rice. 4. Tricarboxylic acid cycle (Krebs cycle)
The third reaction seems to limit the rate of the Krebs cycle. Isocitric acid is dehydrogenated in the presence of NAD-dependent isocitrate dehydrogenase. During the isocitrate dehydrogenase reaction, isocitric acid is simultaneously decarboxylated. NAD-dependent isocitrate dehydrogenase is an allosteric enzyme that requires ADP as a specific activator. In addition, the enzyme needs or ions to manifest its activity.
During the fourth reaction, α-ketoglutaric acid is oxidatively decarboxylated to form the high-energy compound succinyl-CoA. The mechanism of this reaction is similar to the reaction of oxidative decarboxylation of pyruvate to acetyl-CoA; The α-ketoglutarate dehydrogenase complex resembles the pyruvate dehydrogenase complex in its structure. Both in one and in the other case, 5 coenzymes take part in the reaction: TPP, lipoic acid amide, HS-CoA, FAD and NAD +.
The fifth reaction is catalyzed by the enzyme succinyl-CoA synthetase. During this reaction, succinyl-CoA, with the participation of GTP and inorganic phosphate, is converted into succinic acid (succinate). At the same time, the formation of a high-energy phosphate bond of GTP occurs due to the high-energy thioether bond of succinyl-CoA.
As a result of the sixth reaction, succinate is dehydrogenated to fumaric acid. The oxidation of succinate is catalyzed by succinate dehydrogenase,
in the molecule of which the coenzyme FAD is firmly (covalently) bound to the protein. In turn, succinate dehydrogenase is tightly bound to the inner mitochondrial membrane.
The seventh reaction is carried out under the influence of the enzyme fumarate hydratase (fumarase). The resulting fumaric acid is hydrated, the reaction product is malic acid (malate).
Finally, during the eighth reaction of the tricarboxylic acid cycle, L-malate is oxidized to oxaloacetate under the influence of mitochondrial NAD-dependent malate dehydrogenase.
During one turn of the cycle, during the oxidation of one molecule of acetyl-CoA in the Krebs cycle and the system of oxidative phosphorylation, 12 ATP molecules can be formed.
Anaerobic oxidation
Synonyms: substrate phosphorylation, anaerobic ATP synthesis. Goes in the cytoplasm, the split off hydrogen is attached to some other substance. Depending on the substrate, two pathways of anaerobic ATP resynthesis are distinguished: creatine phosphate (creatine kinase, alactate) and glycolytic (glycolysis, lactate). In the first case, the substrate is creatine phosphate, in the second - glucose.
These paths proceed without the participation of oxygen.
Judging by the above, a huge amount of ATP is required. In skeletal muscles, during their transition from a state of rest to contractile activity - 20 times (or even several hundred times) the rate of ATP splitting sharply increases simultaneously.
However, ATP stores in muscles are relatively insignificant (about 0.75% of its mass) and they can only last for 2-3 seconds of intense work.
Fig.15. Adenosine triphosphate (ATP, ATP). Molar mass 507.18g/mol
This is because ATP is a large, heavy molecule ( fig.15). ATP is a nucleotide formed by the nitrogenous base adenine, the five-carbon sugar ribose, and three phosphoric acid residues. Phosphate groups in the ATP molecule are interconnected by high-energy (macroergic) bonds. It has been calculated that if the body contained amount of ATP sufficient for use in within one day, then the weight of a person, even leading a sedentary lifestyle, would be on 75% more.
To sustain a sustained contraction, ATP molecules must be formed during metabolism at the same rate as they are broken down during contraction. Therefore, ATP is one of the most frequently updated substances, so in humans, the lifespan of one ATP molecule is less than 1 minute. During the day, one ATP molecule goes through an average of 2000-3000 resynthesis cycles (the human body synthesizes about 40 kg of ATP per day, but contains about 250 g at any given moment), that is, there is practically no ATP reserve in the body, and for normal life it is necessary to constantly synthesize new ATP molecules.
Thus, to maintain the activity of muscle tissue at a certain level, rapid resynthesis of ATP is required at the same rate as it is consumed. This occurs in the process of rephosphorylation, when ADP and phosphates are combined
ATP synthesis - ADP phosphorylation
In the body, ATP is formed from ADP and inorganic phosphate due to the energy released during the oxidation of organic substances and in the process of photosynthesis. This process is called phosphorylation. In this case, at least 40 kJ / mol of energy must be expended, which is accumulated in macroergic bonds:
ADP + H 3 PO 4 + energy→ ATP + H 2 O
Phosphorylation of ADP
Substrate phosphorylation of ATP Oxidative phosphorylation of ATP
Phosphorylation of ADP is possible in two ways: substrate phosphorylation and oxidative phosphorylation (using the energy of oxidizing substances). The bulk of ATP is formed on mitochondrial membranes during oxidative phosphorylation by H-dependent ATP synthase.
The reactions of ADP phosphorylation and the subsequent use of ATP as an energy source form a cyclic process that is the essence of energy metabolism.
There are three ways in which ATP is generated during muscle fiber contraction.
Three main pathways for ATP resynthesis:
1 - creatine phosphate (CP) system
2 - glycolysis
3 - oxidative phosphorylation
Creatine phosphate (CP) system -
Phosphorylation of ADP by transfer of a phosphate group from creatine phosphate
Anaerobic creatine phosphate resynthesis of ATP.
Fig.16. Creatine Phosphate ( CF) ATP resynthesis system in the body
To maintain the activity of muscle tissue at a certain level rapid resynthesis of ATP is required. This occurs in the process of rephosphorylation, when ADP and phosphates are combined. The most available substance that is used for ATP resynthesis is primarily creatine phosphate ( fig.16), easily transferring its phosphate group to ADP:
CrF + ADP → Creatine + ATP
CRF is a compound of the nitrogen-containing substance creatinine with phosphoric acid. Its concentration in muscles is approximately 2–3%, i.e., 3–4 times higher than that of ATP. A moderate (by 20–40%) decrease in the ATP content immediately leads to the use of CRF. However, at maximum work, creatine phosphate reserves are also quickly depleted. Through ADP phosphorylation creatine phosphate very rapid formation of ATP at the very beginning of the contraction is ensured.
During the rest period, the concentration of creatine phosphate in the muscle fiber rises to a level approximately five times higher than the content of ATP. At the beginning of the contraction, when the ATP concentration begins to decrease and the ADP concentration begins to increase due to the splitting of ATP by the action of myosin ATPase, the reaction shifts towards the formation of ATP due to creatine phosphate. In this case, the energy transition occurs at such a high rate that at the beginning of the contraction, the ATP concentration in the muscle fiber changes little, while the concentration of creatine phosphate falls rapidly.
Although ATP is formed from creatine phosphate very quickly, through a single enzymatic reaction (Fig. 16), the amount of ATP is limited by the initial concentration of creatine phosphate in the cell. In order for a muscle contraction to last longer than a few seconds, the other two sources of ATP formation mentioned above must be involved. After the start of the contraction provided by the use of creatine phosphate, the slower, multi-enzymatic pathways of oxidative phosphorylation and glycolysis are activated, due to which the rate of ATP formation increases to a level corresponding to the rate of ATP splitting.
What is the fastest ATP synthesis system?
The CP (creatine phosphate) system is the fastest ATP resynthesis system in the body, as it involves only one enzymatic reaction. It carries out the transfer of high-energy phosphate directly from CP to ADP with the formation of ATP. However, the ability of this system to resynthesize ATP is limited, since the CP reserves in the cell are small. Since this system does not use oxygen to synthesize ATP, it is considered an anaerobic source of ATP.
How much CF is stored in the body?
The total reserves of CF and ATP in the body would be enough for less than 6 seconds of intense physical activity.
What is the advantage of anaerobic ATP production using CF?
The CF/ATP system is used during short-term intense exercise. It is located on the heads of myosin molecules, that is, directly at the place of energy consumption. The CF/ATF system is used when a person makes rapid movements, such as quickly climbing a mountain, performing high jumps, running a hundred meters, quickly getting out of bed, running away from a bee, or jumping away from a truck while crossing the street.
glycolysis
Phosphorylation of ADP in the cytoplasm
The breakdown of glycogen and glucose under anaerobic conditions to form lactic acid and ATP.
To restore ATP in order to continue intense muscle activity the process includes the following source of energy production - the enzymatic breakdown of carbohydrates in oxygen-free (anaerobic) conditions.
Fig.17. General scheme of glycolysis
The process of glycolysis is schematically represented as follows (p is.17).
The appearance of free phosphate groups during glycolysis makes possible the re-synthesis of ATP from ADP. However, in addition to ATP, two molecules of lactic acid are formed.
Process glycolysis is slower compared to creatine phosphate ATP resynthesis. The duration of muscle work in anaerobic (oxygen-free) conditions is limited due to the depletion of glycogen or glucose reserves and due to the accumulation of lactic acid.
Anaerobic energy production by glycolysis is produced uneconomical with high consumption of glycogen, since only part of the energy contained in it is used (lactic acid is not used during glycolysis, although contains a significant amount of energy).
Of course, already at this stage, part of the lactic acid is oxidized by some amount of oxygen to carbon dioxide and water:
С3Н6О3 + 3О2 = 3СО2 + 3Н2О 41
The resulting energy goes to the resynthesis of carbohydrate from other parts of lactic acid. However, the limited amount of oxygen during very intense physical activity is insufficient to support the reactions aimed at the conversion of lactic acid and the resynthesis of carbohydrates.
Where does ATP come from for physical activity lasting more than 6 seconds?
At glycolysis ATP is formed without the use of oxygen (anaerobically). Glycolysis occurs in the cytoplasm of the muscle cell. In the process of glycolysis, carbohydrates are oxidized to pyruvate or lactate and 2 ATP molecules are released (3 molecules if you start the calculation with glycogen). During glycolysis, ATP is synthesized quickly, but more slowly than in the CF system.
What is the end product of glycolysis - pyruvate or lactate?
When glycolysis proceeds slowly and mitochondria adequately accept reduced NADH, the end product of glycolysis is pyruvate. Pyruvate is converted to acetyl-CoA (a reaction requiring NAD) and undergoes complete oxidation in the Krebs and CPE cycle. When the mitochondria cannot provide adequate pyruvate oxidation or regeneration of electron acceptors (NAD or FADH), pyruvate is converted to lactate. The conversion of pyruvate to lactate reduces the concentration of pyruvate, which prevents the end products from inhibiting the reaction, and glycolysis continues.
When is lactate the main end product of glycolysis?
Lactate is formed when mitochondria cannot adequately oxidize pyruvate or regenerate enough electron acceptors. This occurs at low enzymatic activity of mitochondria, with insufficient oxygen supply, at a high rate of glycolysis. In general, lactate formation is increased during hypoxia, ischemia, bleeding, after carbohydrate intake, high muscle glycogen concentrations, and exercise-induced hyperthermia.
What other ways can pyruvate be metabolized?
Pyruvate is converted to the non-essential amino acid alanine during exercise or dietary deficiencies. Synthesized in skeletal muscles, alanine enters the liver with blood flow, where it turns into pyruvate. Pyruvate is then converted to glucose, which enters the bloodstream. This process is similar to the Cori cycle and is called the alanine cycle.
In the cells of all organisms there are molecules of ATP - adenosine triphosphoric acid. ATP is a universal cell substance, the molecule of which has energy-rich bonds. The ATP molecule is one kind of nucleotide, which, like other nucleotides, consists of three components: a nitrogenous base - adenine, a carbohydrate - ribose, but instead of one it contains three residues of phosphoric acid molecules (Fig. 12). The bonds indicated in the figure by the icon are rich in energy and are called macroergic. Each ATP molecule contains two macroergic bonds.
When a high-energy bond is broken and one molecule of phosphoric acid is cleaved off with the help of enzymes, 40 kJ / mol of energy is released, and ATP is converted into ADP - adenosine diphosphoric acid. With the elimination of one more phosphoric acid molecule, another 40 kJ / mol is released; AMP is formed - adenosine monophosphoric acid. These reactions are reversible, that is, AMP can be converted to ADP, ADP to ATP.
ATP molecules are not only broken down, but also synthesized, so their content in the cell is relatively constant. The importance of ATP in the life of the cell is enormous. These molecules play a leading role in the energy metabolism necessary to ensure the vital activity of the cell and the organism as a whole.
An RNA molecule, as a rule, is a single chain consisting of four types of nucleotides - A, U, G, C. Three main types of RNA are known: mRNA, rRNA, tRNA. The content of RNA molecules in the cell is not constant, they are involved in protein biosynthesis. ATP is the universal energy substance of the cell, in which there are energy-rich bonds. ATP plays a central role in the exchange of energy in the cell. RNA and ATP are found both in the nucleus and in the cytoplasm of the cell.
Any cell, like any living system, has the ability to maintain its composition and all its properties at a relatively constant level. For example, the content of ATP in cells is about 0.04%, and this value is steadfastly maintained, despite the fact that ATP is constantly consumed in the cell during life. Another example: the reaction of the cellular contents is weakly alkaline, and this reaction is stably maintained, despite the fact that acids and bases are constantly formed in the process of metabolism. Not only the chemical composition of the cell, but also its other properties are firmly maintained at a certain level. The high stability of living systems cannot be explained by the properties of the materials from which they are built, since proteins, fats and carbohydrates have little stability. The stability of living systems is active, it is due to complex processes of coordination and regulation.
Consider, for example, how the constancy of the ATP content in the cell is maintained. As we know, ATP is consumed by the cell when it performs any activity. The synthesis of ATP occurs as a result of processes without oxygen and oxygen breakdown of glucose. Obviously, the constancy of the ATP content is achieved due to the exact balancing of both processes - the consumption of ATP and its synthesis: as soon as the ATP content in the cell decreases, the processes without oxygen and oxygen breakdown of glucose immediately turn on, during which ATP is synthesized and the ATP content in the cell increases. When the level of ATP reaches the norm, ATP synthesis slows down.
Turning on and off the processes that ensure the maintenance of the normal composition of the cell occurs automatically in it. Such regulation is called self-regulation or auto-regulation.
The basis for the regulation of cell activity is information processes, i.e., processes in which communication between the individual links of the system is carried out using signals. The signal is a change that occurs in some part of the system. In response to the signal, a process is started, as a result of which the change that has occurred is eliminated. When the normal state of the system is restored - this serves as a new signal to shut down the process.
How does the cell signaling system work, how does it provide autoregulation processes in it?
The reception of signals inside the cell is carried out by its enzymes. Enzymes, like most proteins, have an unstable structure. Under the influence of a number of factors, including many chemical agents, the structure of the enzyme is disturbed and its catalytic activity is lost. This change, as a rule, is reversible, i.e., after the elimination of the active factor, the structure of the enzyme returns to normal and its catalytic function is restored.
The mechanism of cell autoregulation is based on the fact that the substance, the content of which is regulated, is capable of specific interaction with the enzyme that generates it. As a result of this interaction, the structure of the enzyme is deformed and its catalytic activity is lost.
The cell autoregulation mechanism works as follows. We already know that the chemicals produced in a cell usually result from several successive enzymatic reactions. Remember the oxygen-free and oxygen-free processes of glucose breakdown. Each of these processes is a long series - at least a dozen consecutive reactions. It is quite obvious that for the regulation of such multinomial processes, it is sufficient to turn off any one link. It is enough to turn off at least one reaction - and the whole line will stop. It is in this way that the regulation of the ATP content in the cell is carried out. While the cell is at rest, the ATP content in it is about 0.04%. At such a high concentration of ATP, it reacts with one of the enzymes without the oxygen breakdown of glucose. As a result of this reaction, all molecules of this enzyme are deprived of activity and conveyor lines without oxygen and oxygen processes are inactive. If, due to any activity of the cell, the concentration of ATP in it decreases, then the structure and function of the enzyme are restored and without oxygen and oxygen processes are launched. As a result, ATP is produced, its concentration increases. When it reaches the norm (0.04%), the conveyor without oxygen and oxygen processes automatically turns off.
2241-2250
2241. Geographical isolation leads to speciation, since in the populations of the original species
A) divergence
B) convergence
B) aromorphosis
D) degeneration
2242. Non-renewable natural resources of the biosphere include
A) lime deposits
B) tropical forests
B) sand and clay
D) coal
2243. What is the probability of manifestation of a recessive trait in the phenotype in the offspring of the first generation, if both parents have the Aa genotype?
A) 0%
B) 25%
C) 50%
D) 75%
Abstract
2244. Energy-rich bonds between phosphoric acid residues are present in the molecule
A) squirrel
B) ATP
B) mRNA
D) DNA
2245. On what grounds is the animal depicted in the figure assigned to the class of insects?
A) three pairs of walking legs
B) two simple eyes
c) one pair of transparent wings
D) dismemberment of the body into head and abdomen
Abstract
2246. A zygote, unlike a gamete, is formed as a result of
A) fertilization
B) parthenogenesis
B) spermatogenesis
D) I division of meiosis
2247. Infertile hybrids in plants are formed as a result of
A) intraspecific crossing
B) polyploidization
B) distant hybridization
D) analyzing cross
How much ATP is in the body?
2249. In Rh-negative people, compared with Rh-positive, blood erythrocytes differ in composition
A) lipids
B) carbohydrates
B) minerals
D) proteins
2250. When cells of the temporal lobe of the cerebral cortex are destroyed, a person
A) gets a distorted idea of the shape of objects
B) does not distinguish between the strength and height of the sound
B) loses coordination
D) does not distinguish visual signals
© D.V. Pozdnyakov, 2009-2018
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1. What words are missing in the sentence and replaced by letters (а-г)?
"The composition of the ATP molecule includes a nitrogenous base (a), a five-carbon monosaccharide (b) and (c) a residue (d) of an acid."
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. Find similarities and differences.
In fact, ATP is a derivative of the adenyl nucleotide of RNA (adenosine monophosphate, or AMP). The composition of the molecules of both substances includes the nitrogenous base adenine and the five-carbon sugar ribose. The differences are due to the fact that in the composition of the adenyl nucleotide of RNA (as in the composition of any other nucleotide) there is only one phosphoric acid residue, and there are no macroergic (high-energy) bonds. The ATP molecule contains three phosphoric acid residues, between which there are two macroergic bonds, so ATP can act as an accumulator and energy carrier.
3. What is the process of ATP hydrolysis?
ATP: energy currency
ATP synthesis? What is the biological role of ATP?
In the process of hydrolysis, one residue of phosphoric acid is cleaved from the ATP molecule (dephosphorylation). In this case, the macroergic bond is broken, 40 kJ / mol of energy is released and ATP is converted into ADP (adenosine diphosphoric acid):
ATP + H2O → ADP + H3PO4 + 40 kJ
ADP can undergo further hydrolysis (which happens rarely) with the elimination of another phosphate group and the release of a second "portion" of energy. In this case, ADP is converted to AMP (adenosine monophosphoric acid):
ADP + H2O → AMP + H3PO4 + 40 kJ
The synthesis of ATP occurs as a result of the addition of a phosphoric acid residue to the ADP molecule (phosphorylation). This process is carried out mainly in mitochondria and chloroplasts, partly in the hyaloplasm of cells. For the formation of 1 mol of ATP from ADP, at least 40 kJ of energy must be expended:
ADP + H3PO4 + 40 kJ → ATP + H2O
ATP is a universal store (accumulator) and carrier of energy in the cells of living organisms. In almost all biochemical processes that take place in cells with energy costs, 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, cell division occurs, muscles work, a constant body temperature of warm-blooded animals is maintained, etc.
4. What bonds are called macroergic? What functions can substances containing macroergic bonds perform?
Macroergic bonds are called bonds, upon breaking of which a large amount of energy is released (for example, the breaking of each ATP macroergic bond is accompanied by the release of 40 kJ / mol of energy). Substances containing macroergic bonds can serve as accumulators, carriers and energy suppliers for various life processes.
5. The general formula of ATP is С10H16N5O13P3. Hydrolysis of 1 mol of ATP to ADP releases 40 kJ of energy. How much energy is released during the hydrolysis of 1 kg of ATP?
● Calculate the molar mass of ATP:
M (С10H16N5O13P3) = 12 × 10 + 1 × 16 + 14 × 5 + 16 × 13 + 31 × 3 = 507 g/mol.
● Hydrolysis of 507 g of ATP (1 mol) releases 40 kJ of energy.
This means that during the hydrolysis of 1000 g of ATP, the following will be released: 1000 g × 40 kJ: 507 g ≈ 78.9 kJ.
Answer: during the hydrolysis of 1 kg of ATP to ADP, about 78.9 kJ of energy will be released.
6. ATP molecules labeled with radioactive phosphorus 32P at the last (third) phosphoric acid residue were introduced into one cell, and ATP molecules labeled with 32P at the first (closest to ribose) residue were introduced into the other. After 5 min, the content of inorganic phosphate ion labeled with 32P was measured in both cells. Where is it higher and why?
The last (third) residue of phosphoric acid is easily cleaved off during ATP hydrolysis, while the first one (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 with the last (third) phosphoric acid residue, has been introduced.
Dashkov M.L.
Website: dashkov.by
An RNA molecule, unlike DNA, is usually a single chain of nucleotides, which is much shorter than DNA. However, the total mass of RNA in a cell is greater than that of DNA. RNA molecules are found both in the nucleus and in the cytoplasm.
Three main types of RNA are known: informational, or matrix, - mRNA; ribosomal - rRNA, transport - tRNA, which differ in the shape, size and function of the molecules. Their main function is participation in protein biosynthesis.
You see that the RNA molecule, like the DNA molecule, consists of four types of nucleotides, three of which contain the same nitrogenous bases as the DNA nucleotides (A, G, C). However, instead of the nitrogenous base of thymine, the composition of RNA includes another nitrogenous base - uracil (U). Thus, the composition of the nucleotides of the RNA molecule includes nitrogenous bases: A, G, C, U. In addition, instead of the carbohydrate deoxyribose, RNA contains ribose.
In the cells of all organisms there are ATP molecules - adenosine triphosphoric acid. ATP is a universal cell substance, the molecule of which has energy-rich bonds. The ATP molecule is one kind of nucleotide, which, like other nucleotides, consists of three components: a nitrogenous base - adenine, a carbohydrate - ribose, but instead of one it contains three residues of phosphoric acid molecules. Each ATP molecule contains two macroergic bonds.
When a high-energy bond is broken and one molecule of phosphoric acid is cleaved off with the help of enzymes, 40 kJ / mol of energy is released, and ATP is converted into ADP - adenosine diphosphoric acid. With the elimination of one more phosphoric acid molecule, another 40 kJ / mol is released; AMP is formed - adenosine monophosphoric acid. These reactions are reversible, that is, AMP can be converted to ADP, ADP to ATP.
ATP molecule - what is it and what is its role in the body
ATP molecules are not only broken down, but also synthesized, so their content in the cell is relatively constant. The importance of ATP in the life of the cell is enormous. These molecules play a leading role in the energy metabolism necessary to ensure the vital activity of the cell and the organism as a whole.
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