Aerobic and anaerobic synthesis of atf. Resynthesis of ATB - the basic principles of biochemical sports. General indicators and energy capabilities of ongoing reactions
The process of ATP resynthesis during operation can be schematically expressed by the following equation:
ADP + H 3 PO 4 + energy → ATP + H 2 O
Phosphorylation of ADP with inorganic phosphate under physiological conditions requires energy consumption in the amount of about 9 kcal / mol of ATP. The required amount of energy can be released in two types of processes: aerobic, which require oxygen for their flow, and anaerobic, which resynthesize ATP without the participation of oxygen.
Before proceeding to the direct characterization of the various pathways of ATP resynthesis, let us dwell on the indicators that allow them to be compared, to assess the possibilities, advantages and disadvantages of these processes. These indicators include the maximum power of the process, the speed of its deployment, metabolic capacity and efficiency.
The maximum power of the ATP resynthesis process is estimated by the largest amount of energy that a particular process can supply to ensure ATP resynthesis per unit time (or the amount of ATP resynthesized per unit time). The maximum power is usually expressed in calories (cal), kilocalories (kcal), as well as joules (J) or kilojoules (kJ) per unit of time (second or minute) per kg of human body weight.
The rate of development of the ATP resynthesis process is estimated by the time from the start of work to the moment this process reaches its maximum power. It is expressed in seconds or minutes.
Metabolic capacity is the total amount of energy that can be released during a process and used for ATP resynthesis. The metabolic capacity is expressed in kilocalories or kiloJoules.
The efficiency of energy supply processes is determined by the ratio of useful energy expended (for ATP resynthesis) to the total amount of energy released during this process. Most often, efficiency is expressed as a percentage.
It is customary to distinguish between thermodynamic, metabolic and mechanical efficiency. Thermodynamic efficiency is estimated by the fraction of energy released during the breakdown of ATP, which is converted into mechanical work. In accordance with modern scientific data, 40-49% (0.4) of the energy released during the breakdown of ATP is converted into mechanical work.
Metabolic efficiency shows how much of the energy released in the course of chemical transformations is fixed in the high-energy phosphate bonds of ATP. In particular, in the process of aerobic oxidation of carbohydrates, the maximum metabolic efficiency is about 60% (0.6).
Mechanical efficiency characterizes the body's ability to use the energy of chemical bonds from various sources to ensure muscle work. It is calculated as the product of thermodynamic and metabolic efficiency. Thus, approximately 25% (0.4 × 0.6 = 0.24) of the energy released during aerobic digestion of carbohydrates is converted directly into mechanical work.
The main process that carries out ATP resynthesis is aerobic oxidation, which fully meets the energy needs of the body in the conditions of daily activities. Aerobic conversions are characterized by a high metabolic capacity. The total amount of energy that the aerobic process can supply to ensure muscle work is many times higher than that of anaerobic transformations.
The main energy substrates of aerobic transformations are carbohydrates and fats, the reserves of which in the human body are quite large. In addition, protein metabolism products can be used as a source of energy. Thus, from the side of energy substrates, there are practically no restrictions on aerobic transformations. However, when performing voluminous, prolonged muscle work, problems may arise with the delivery of energy substrates to working organs and tissues (primarily to muscles) from the depot.
In the process of aerobic oxidation, the body does not accumulate intermediate products of energy metabolism. The end products of aerobic transformations (H 2 O and CO 2) are easily eliminated from the body.
As already indicated, the aerobic pathway of ATP resynthesis is highly efficient. Directly for ATP resynthesis, up to 60% of the energy released during aerobic transformations is used (in the absence of uncoupling of oxidation with ATP resynthesis).
On the other hand, aerobic oxidation is characterized by a slow deployment rate and limited maximum power compared to anaerobic transformations. In untrained individuals, aerobic resynthesis of ATP reaches its maximum intensity 3-4 minutes after the start of intense muscular work. Systematic training will shorten this time. In persons with a high degree of fitness who have completed a preliminary warm-up, the aerobic process develops to a maximum by the end of the first minute of work or a little later. Considering that many sports exercises, in terms of their duration, fall into the zone of incomplete deployment of aerobic processes, such a speed can be considered as insufficiently high.
Even with the maximum power of aerobic transformations, the rate of ATP resynthesis remains relatively low and cannot provide replenishment of ATP costs during intensive work. In the presence of only an aerobic mechanism of energy supply, the body would not have the ability to quickly switch from a state of rest to intense work, to quickly increase power during the exercise, to perform short-term intense exercises of a speed-strength nature.
Anaerobic processes of ATP resynthesis seem to compensate for the deficiencies of the aerobic pathway. They have a significantly higher deployment rate and maximum power, but they are significantly inferior to the aerobic process in terms of metabolic capacity.
There are three main anaerobic processes for ATP resynthesis: creatine phosphokinase reaction, glycolysis, and myokinase reaction. In all three cases, ATP resynthesis is carried out by the interaction of ADP with high-energy compounds either present in muscle tissue (creatine phosphate and ADP), or formed during anaerobic oxidative transformations of carbohydrates (diphosphoglyceric and phosphoenolpyruvic acids).
Let us consider sequentially each of the three main anaerobic mechanisms of ATP resynthesis.
In the process of contraction, ATP supplies the necessary energy for the formation of the actomyosin complex, and in the process of muscle relaxation it provides energy for the active transport of calcium ions into the reticulum. To maintain the contractile function of the muscle, the concentration of ATP in it must be at a constant level of 2 to 5 mmol / kg.
Therefore, during muscular activity, adenosine triphosphoric acid must be restored at the same rate as it is broken down in the course of contraction, which is carried out by separate biochemical mechanisms of its resynthesis.
Energy sources of ATP resynthesis in skeletal muscle and other tissues are energy-rich phosphate-containing substances. They are present in tissues (creatine phosphate, adenosine diphosphate) or are formed during the catabolism of glycogen, fatty acids and other energy substrates. In addition, as a result of aerobic oxidation of various substances, proton gradient energies appear on the mitochondrial membrane.
Resynthesis adenosine triphosphate can be carried out in reactions without the participation of oxygen ( anaerobic mechanisms ) or with his participation ( aerobic mechanism ). Under normal conditions, the resynthesis of ATP in the muscles occurs predominantly through the aerobic route. During intense physical work, when the delivery of oxygen to the muscles is difficult, the anaerobic mechanisms of ATP resynthesis are also activated. Three types of anaerobic and one aerobic recovery of adenosine triphosphate have been identified in human skeletal muscles.
TO anaerobic mechanisms include creatine phosphokinase (phosphogenic or alactate), glycolytic (lactate) and myokinase mechanisms.
Aerobic Mechanism of ATP Resynthesis consists in oxidative phosphorylation that occurs in mitochondria, the amount of which in skeletal muscles increases significantly during aerobic training. Energy substrates for aerobic oxidation are glucose, fatty acids, partially amino acids, as well as intermediate metabolites of glycolysis (lactic acid) and fatty acid oxidation (ketone bodies).
Each mechanism has different energy capabilities, which are evaluated according to the following criteria: maximum power, deployment speed, metabolic capacity and efficiency.
Maximum power is the highest rate of ATP formation in this metabolic process. It limits the extreme intensity of the work performed by the mechanism used.
Deployment speed- the time to reach the maximum power of this pathway of resynthesis of adenosine triphosphate from the beginning of work.
Metabolic capacity- the total amount of ATP that can be obtained in the used mechanism of ATP resynthesis due to the amount of reserves of energy substrates. Capacity limits the amount of work done. Metabolic efficiency is that part of the energy that is accumulated in the high-energy bonds of adenosine-riphosphate. It determines the efficiency of the work performed and is estimated by the total value of the efficiency, which represents the ratio of all the useful energy expended to its total amount released during the current metabolic process.
Overall efficiency when converting the energy of metabolic processes into mechanical work, it depends on two indicators:
- phosphorylation efficiency;
- efficiency of chemomechanical coupling (efficiency of conversion of ATP into mechanical work).
Efficiency of Chemomechanical Coupling in the processes of aerobic and anaerobic metabolism is approximately the same and amounts to 50%.
Phosphorylation efficiency the highest in the alactate anaerobic process - about 80%, and the lowest in anaerobic glycolysis - on average 44%. In the aerobic process, it is about 60%.
Thus, anaerobic mechanisms have a high maximum power and efficiency of ATP formation, but a short retention time and small capacity, due to small reserves of energy substrates. For example, the maximum power of the creatine phosphokinase reaction develops already at 0.5-0.7 s of intense work and is maintained for 10-15 s in untrained people and up to 25-30 s of highly trained athletes and is 3.8 kJ / kg per minute.
Glycolytic mechanism of ATP resynthesis differs in low efficiency. Most of the energy remains in the molecules of the resulting lactic acid. The concentration of the latter is in direct proportion to the power and duration of work, and can be isolated only by aerobic oxidation.
Glycolysis- this is the main way of energy education in exercises of submaximal power, the maximum duration of which is from 30 s to 2.5 minutes (running at medium distances, swimming at 100 and 200 m, etc.).
The glycolytic mechanism of energy production serves as a biochemical basis for the body's special high-speed endurance.
The myokinase reaction occurs in the muscles with a significant increase in the concentration of ADP in the sarcoplasm. This situation occurs with severe muscle fatigue, when other resynthesis pathways are no longer possible.
Thus, anaerobic mechanisms are the main ones in the energy supply of short-term high-intensity exercise .
When adapting to intense loads, the activity of enzymes of anaerobic mechanisms and reserves of energy mechanisms increases: the content of creatine phosphate in skeletal muscles can increase by 1.5-2 times, and the content of glycogen - almost 3 times.
Updated: 20 June 2013 Hits: 85,079Anaerobic pathways for ATP resynthesis are complementary pathways. There are two such pathways, the creatine phosphate pathway and the lactate pathway.
Creatine phosphate pathway related to substance creatine phosphate... Creatine phosphate consists of the substance creatine, which binds to the phosphate group by a high-energy bond. Creatine phosphate in muscle cells is contained at rest 15 - 20 mmol / kg.
Creatine phosphate has a large energy reserve and a high affinity for ADP. Therefore, it easily interacts with ADP molecules that appear in muscle cells during physical work as a result of the ATP hydrolysis reaction. In the course of this reaction, the remainder of phosphoric acid with an energy reserve is transferred from creatine phosphate to the ADP molecule with the formation of creatine and ATP.
Creatine Phosphate + ADP → Creatine + ATP.
This reaction is catalyzed by an enzyme creatine kinase... This pathway of ATP resynthesis is sometimes called creatine kinase.
The creatine kinase reaction is reversible, but biased towards the formation of ATP. Therefore, it begins to be carried out as soon as the first ADP molecules appear in the muscles.
Creatine phosphate is a fragile substance. The formation of creatine from it occurs without the participation of enzymes. Not used by the body, creatine is excreted in the urine. In men, the excretion of creatinine in the urine ranges from 18-32 mg / day . kg of body weight, and in women - 10-25 mg / day . kg (this is the cryatinine coefficient). The synthesis of creatine phosphate occurs during rest from excess ATP. With moderate muscle work, the reserves of creatine phosphate can be partially restored. Muscle stores of ATP and creatine phosphate are also called phosphagens.
Maximum power this path is 900-1100 cal / min-kg, which is three times higher than the corresponding indicator of the aerobic path.
Deployment time only 1 - 2 sec.
Running time at maximum speed only 8 - 10 sec.
The main advantages of the creatine phosphate pathway of ATP formation are:
short deployment time (1-2 sec);
high power.
This reaction is the main source of energy for maximum power exercises: sprinting, throwing jumps, and barbell lifts. This response can be triggered repeatedly during exercise, making it possible to rapidly increase the power of the work being done.
Biochemical assessment of the state of this pathway of ATP resynthesis is usually carried out by two indicators: creatine ratio and alactate debt.
Creatine ratio - this is the release of creatine per day. This indicator characterizes the reserves of creatine phosphate in the body.
Alactate oxygen debt- This is an increase in oxygen consumption in the next 4 - 5 minutes, after a short-term exercise of maximum power. This excess oxygen is required to ensure a high rate of tissue respiration immediately after the end of the load to create an increased concentration of ATP in muscle cells. For highly qualified athletes, the value of the alactate duty after the fulfillment of loads of maximum power is 8 - 10 liters.
Glycolytic pathway ATP resynthesis, as well as creatine phosphate, is anaerobic. The source of energy required for ATP resynthesis in this case is muscle glycogen. During anaerobic decomposition of glycogen from its molecule under the action of the phosphorylase enzyme, terminal residues of glucose are alternately cleaved in the form of glucose-1-phosphate. Further, the molecules of glucose-1-phosphate, after a series of successive reactions, are converted into lactic acid. This process is called glycolysis. As a result of glycolysis, intermediate products are formed containing phosphate groups linked by high-energy bonds. This bond is easily transferred to ADP to form ATP. At rest, glycolysis reactions proceed slowly, but during muscular work, its speed can increase 2000 times, and already in the pre-start state.
Maximum power - 750-850 cal / min-kg, which is two times higher than with tissue respiration. Such a high power is explained by the content in cells of a large store of glycogen and the presence of a mechanism for activating key enzymes.
Deployment time 20-30 seconds .
Operating time with maximum power - 2-3 minutes.
The glycolytic mode of formation of ATP has several advantages before the aerobic route:
it reaches maximum power faster;
has a higher value of maximum power;
does not require the participation of mitochondria and oxygen.
However, this path has its own limitations:
the process is low-cost;
the accumulation of lactic acid in muscles significantly disrupts their normal functioning and contributes to muscle fatigue.
The overall result of glycolysis can be presented in the form of the following equations:
C 6 H 12 O 6 + ADP + 2 H 3 PO 4 C 3 H 6 O 3 + 2 ATP + 2 H 2 O;
glucose lactic acid
n + 3 ADP + 3 H 3 PO 4 C 3 H 6 O 3 + n _ 1 + 3 ATP + 2 H 2 O
glycogen lactic acid
Scheme of anaerobic and aerobic glycolysis
Two biochemical techniques are used to assess glycolysis - measuring the concentration of lactate in the blood, measuring the pH of the blood and determining the alkaline reserve of the blood.
The lactate content in urine is also determined. This provides information on the total contribution of glycolysis to the energy supply of the exercise performed during the workout.
Another important indicator is lactate oxygen debt. Lactate oxygen debt is an increased oxygen consumption in the next 1-1.5 hours after the end of muscle work. This excess oxygen is required to eliminate lactic acid produced during muscle work. Well-trained athletes have an oxygen demand of 20-22 liters. By the value of lactic debt, one is judged on the capabilities of a given athlete with loads of submaximal power.
Quantitative criteria for the pathways of ATP resynthesis. Aerobic pathway for ATP resynthesis. Anaerobic pathways for ATP resynthesis. Relationships between different pathways of ATP resynthesis during muscle work.
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Lecture 8. Topic: ENERGY SUPPLY OF MUSCLE CONTRACTION.
Questions:
1. Quantitative criteria for the pathways of ATP resynthesis.
4. Relationships between different pathways of ATP resynthesis during muscle work. Areas of relative power of muscle work.
Topic : BIOCHEMICAL SHIFTS DURING MUSCLE WORK.
Questions:
1. The main mechanisms of neuro-humoral regulation of muscle activity.
2. Biochemical changes in skeletal muscles.
3. Biochemical changes in the brain and myocardium.
4. Biochemical changes in the liver.
5. Biochemical changes in the blood.
6. Biochemical changes in urine.
- Quantitative criteria for the pathways of ATP resynthesis.
Muscle contraction and relaxation require energy, which is generated whenhydrolysis of ATP molecules.
However, the reserves of ATP in the muscle are insignificant, they are enough for the muscle to work for 2 seconds. The formation of ATP in the muscles is called ATP resynthesis.
Thus, there are two parallel processes in the muscles - ATP hydrolysis and ATP resynthesis.
ATP resynthesis, unlike hydrolysis, can proceed in different ways, and in total, depending on the energy source, they are distinguished by three: aerobic (basic), creatine phosphate and lactate.
For quantitative characteristics of various pathways of ATP resynthesisusually several criteria are used.
1. Maximum power or maximum speed -this is the largest amount of ATP that can be formed per unit of time due to a given resynthesis pathway. The maximum power is measured in calories or joules, assuming that one mmol of ATP corresponds to physiological conditions of about 12 calories or 50 J. Therefore, this criterion has the dimension of cal / min-kg of muscle tissue or J / min-kg of muscle tissue.
2. Deployment time- this is the minimum time required for the ATP resynthesis to reach its highest rate, that is, to achieve maximum power. This criterion is measured in units of time.
3. Time of maintaining or maintaining maximum power -this is the longest time for the functioning of this pathway of ATP resynthesis with maximum power.
4. Metabolic capacity -it is the total amount of ATP that can be produced during muscle work due to this pathway of ATP resynthesis.
Depending on oxygen consumption resynthesis pathways are divided into aerobic and anaerobic.
2. Aerobic pathway of ATP resynthesis.
Aerobic pathway of ATP resynthesisotherwise calledtissue respiration -it is the main mode of ATP formation in the mitochondria of muscle cells. In the course of tissue respiration, two hydrogen atoms are taken away from the oxidized substance and are transferred along the respiratory chain to molecular oxygen delivered to the muscles by blood, resulting in water. Due to the energy released during the formation of water, ATP molecules are synthesized from ADP and phosphoric acid. Usually, for each water molecule formed, there is a synthesis of three ATP molecules.
Most often, hydrogen is subtracted from the intermediate products of the tricarboxylic acid cycle (TCA). TCA is the final stage of catabolism, during which acetyl coenzyme A is oxidized to carbon dioxide and water. During this process, four pairs of hydrogen atoms are subtracted from the acids listed above, and therefore 12 ATP molecules are formed during the oxidation of one molecule of acetyl coenzyme A.
In turn, acetyl coenzyme A can be formed from carbohydrates, fats, amino acids, that is, through this compound, carbohydrates, fats and amino acids are involved in the TCA.
The rate of aerobic metabolism of ATP is controlled by the content in muscle cells A DF, which is an activator of tissue respiration enzymes. During muscular work, an accumulation of A DF. Excess A DF accelerates tissue respiration, and it can reach its maximum intensity.
Another activator of ATP resynthesis is carbon dioxide. An excess of this gas in the blood activates the respiratory center in the brain, which ultimately leads to an increase in the speed of blood circulation and an improvement in the supply of oxygen to the muscle.
Maximum powerthe aerobic pathway is 350-450 cal / min-kg. Compared to the anaerobic pathways of ATP resynthesis, tissue respiration has lower rates, which is limited by the rate of oxygen delivery to the muscles. Therefore, due to the aerobic pathway of ATP resynthesis, only physical activity of moderate power can be carried out.
Deployment timeis 3-4 minutes, but for well-trained athletes it can be 1 minute. This is due to the fact that the delivery of oxygen to mitochondria requires restructuring of almost all body systems.
Runtime at maximum poweris tens of minutes. This makes it possible to use this path for prolonged muscle work.
Compared to other ATP resynthesis processes occurring in muscle cells, the aerobic pathway has a number of advantages.
1. Economical: 39 ATP molecules are formed from one glycogen molecule, with anaerobic glycolysis only 3 molecules.
2. Versatility Various substances act as initial substrates: carbohydrates, fatty acids, ketone bodies, amino acids.
3. Very long duration of work. At rest, the rate of aerobic resynthesis of ATP may be low, but with physical exertion, it can become maximum.
However, there are also disadvantages.
1. Obligatory oxygen consumption, which is limited by the rate of oxygen delivery to the muscles and the rate of oxygen penetration through the mitochondrial membrane.
2. Long deployment time.
3. Low power in maximum value.
Therefore, the muscle activity inherent in most sports cannot be fully obtained by this way of ATP resynthesis.
In sports practice, the following indicators are used to assess aerobic resynthesis:maximum oxygen consumption (MOC), aerobic metabolism threshold (PAO), anaerobic metabolism threshold (TANM) and oxygen intake.
IPC - it is the maximum possible rate of oxygen consumption by the body during physical work. The higher the VO2 max, the higher the rate of tissue respiration. The more trained the person, the higher the VO2 max. The BMD is usually calculated per 1 kg of body weight. In people who are not involved in sports, the IPC is 50 ml / min-kg, and in trained people it reaches 90 ml / min-kg.
In sports practice, VO2 max is also used to characterize the relative power of aerobic work, which is expressed as a percentage of VO2 max. For example, the relative power of work performed with an oxygen consumption of 3 L / min by an athlete with an IPC of 6 L / min will be 50% of the IPC level.
PAO Is the highest relative power of work, measured by oxygen consumption as a percentage in relation to the IPC. Large PAO values indicate a better development of aerobic resynthesis.
ANSP - it is the minimum relative power of operation, also measured as a percentage of oxygen consumption in relation to the IPC. A high TANM indicates that aerobic resynthesis is higher per unit time, therefore, glycolysis is activated at much higher loads.
Oxygen coming -this is the amount of oxygen (above the working level) used during the execution of a given load to ensure aerobic resynthesis of ATP. Oxygen supply characterizes the contribution of tissue respiration to the energy supply of all the work done. Oxygen supply is often used to assess all aerobic work done.
Under the influence of systematic training in muscle cells, the number of mitochondria increases, the oxygen-transport function of the body improves, the amount of myoglobin in muscles and hemoglobin in the blood increases.
3. Anaerobic pathways for ATP resynthesis.
Anaerobic pathways for ATP resynthesisAre additional paths. There are two such pathways, the creatine phosphate pathway and the lactate pathway.
Creatine phosphate pathwayrelated to substancecreatine phosphate... Creatine phosphate consists of the substance creatine, which binds to the phosphate group by a high-energy bond. Creatine phosphate in muscle cells is contained at rest 15 - 20 mmol / kg.
Creatine phosphate has a large energy reserve and a high affinity for ADP. Therefore, it easily interacts with ADP molecules that appear in muscle cells during physical work as a result of the ATP hydrolysis reaction. In the course of this reaction, the remainder of phosphoric acid with an energy reserve is transferred from creatine phosphate to the ADP molecule with the formation of creatine and ATP.
Creatine Phosphate + ADP → Creatine + ATP.
This reaction is catalyzed by an enzyme creatine kinase ... This pathway of ATP resynthesis is sometimes called creatine kinase.
The creatine kinase reaction is reversible, but biased towards the formation of ATP. Therefore, it begins to be carried out as soon as the first ADP molecules appear in the muscles.
Creatine phosphate is a fragile substance. The formation of creatine from it occurs without the participation of enzymes. Not used by the body, creatine is excreted in the urine. In men, the excretion of creatinine in the urine ranges from 18-32 mg / day. kg of body weight, and in women - 10-25 mg / day. kg (this is the cryatinine coefficient). The synthesis of creatine phosphate occurs during rest from excess ATP. With moderate muscle work, the reserves of creatine phosphate can be partially restored. Muscle stores of ATP and creatine phosphate are also called phosphagens.
Maximum powerthis path is 900-1100 cal / min-kg, which is three times higher than the corresponding indicator of the aerobic path.
Deployment time only 1 - 2 sec.
Running time at maximum speedonly 8 - 10 sec.
The main advantage of the creatine phosphate pathway of ATP formation is
- short deployment time (1-2 sec);
- high power.
This reaction is the main source of energy for maximum power exercises: sprinting, throwing jumps, and barbell lifts. This response can be triggered repeatedly during exercise, making it possible to rapidly increase the power of the work being done.
Biochemical assessment of the state of this pathway of ATP resynthesis is usually carried out by two indicators: creatine ratio and alactate debt.
Creatine ratio -this is the release of creatine per day. This indicator characterizes the reserves of creatine phosphate in the body.
Alactate oxygen debt Is increase in oxygen consumption in the next 4 - 5 minutes, after performing a short-term exercise of maximum power.This excess oxygen is required to ensure a high rate of tissue respiration immediately after the end of the load to create an increased concentration of ATP in muscle cells. For highly qualified athletes, the value of the alactate duty after performing the loads of maximum power is 8 - 10 liters.
Glycolytic pathway ATP resynthesis , as well as creatine phosphate is anaerobic. The source of energy required for ATP resynthesis in this case is muscle glycogen. During anaerobic decomposition of glycogen from its molecule under the action of the phosphorylase enzyme, terminal residues of glucose are alternately cleaved in the form of glucose-1-phosphate. Further, the molecules of glucose-1-phosphate, after a series of successive reactions, are converted intolactic acid.This process is called glycolysis. As a result of glycolysis, intermediate products are formed containing phosphate groups linked by high-energy bonds. This bond is easily transferred to ADP to form ATP. At rest, glycolysis reactions proceed slowly, but during muscular work, its speed can increase 2000 times, and already in the pre-start state.
Maximum power -750 - 850 cal / min-kg, which is two times higher than with tissue respiration. Such a high power is explained by the content in cells of a large store of glycogen and the presence of a mechanism for activating key enzymes.
Deployment time 20-30 seconds.
Operating time with maximum power - 2-3 minutes.
The glycolytic mode of formation of ATP has several advantages before the aerobic route:
- it reaches maximum power faster,
- has a higher value of maximum power,
- does not require the participation of mitochondria and oxygen.
However, this path has its own limitations :
- the process is low-cost,
- the accumulation of lactic acid in the muscles significantly disrupts their normal functioning and contributes to muscle fatigue.
The overall result of glycolysis can be presented in the form of the following equations:
C 6 H 12 O 6 + ADP + 2 H 3 PO 4 C 3 H 6 O 3 + 2 ATP + 2 H 2 O;
Dairy glucose
Acid
[C 6 H 10 O 5] n + 3 ADP + 3 H 3 PO 4 C 3 H 6 O 3 + [C 6 H 10 O 5] n _ 1 + 3 ATP + 2 H 2 O
Glycogen Dairy
Acid
Scheme of anaerobic and aerobic glycolysis
Two biochemical techniques are used to assess glycolysis measuring the concentration of lactate in the blood, measuring the pH of the blood and determining the alkaline reserve of the blood.
The lactate content in urine is also determined. This provides information on the total contribution of glycolysis to the energy supply of the exercise performed during the workout.
Another important indicator islactate oxygen debt.Lactate oxygen debt is an increased oxygen consumption in the next 1 to 1.5 hours after the end of muscle work. This excess oxygen is required to eliminate lactic acid produced during muscle work. Well-trained athletes have an oxygen demand of 20 - 22 liters. By the value of lactic debt, one is judged on the capabilities of a given athlete with loads of submaximal power.
4. Correlation between different pathways of ATP resynthesis during muscle work. Areas of relative power of muscle work.
During any muscular work, all three pathways of ATP resynthesis function, but they are included sequentially.In the first seconds of work, ATP resynthesis occurs due to the creatine phosphate reaction, then glycolysis is activated, and, finally, as work continues, tissue respiration comes to replace glycolysis.
The specific contribution of each of the mechanisms of ATP formation to the energy supply of muscle movements depends on the intensity and duration of physical activity.
During short-term, but very intense work (for example, running 100 meters), the main source of ATP is the creatine kinase reaction. With more intense work (for example, at medium distances), most of the ATP is formed due to glycolysis. When performing exercises of long duration, but of moderate power, the energy supply of the muscles is carried out mainly due to aerobic oxidation.
At present, various classifications of muscular work power have been adopted. In sports biochemistry, the most commonly used classification is based on the fact that power is due to the ratio between the three main pathways of ATP resynthesis. According to this classification, there are four zones of relative power of muscle work:maximum, submaximal, large and moderate.
Maximum powercan develop when working for 15 - 20 seconds. The main source of ATP in this work is creatine phosphate. Only at the very end is the creatine kinase reaction replaced by glycolysis. Examples of physical exercises performed in the maximum power zone are sprinting, long and high jumping, some gymnastic exercises, barbell lifting, and some others. The maximum power for these exercises is denoted asmaximum anaerobic power.
Work in the zone submaximal aerobic capacityhas a duration of up to 5 minutes. The leading mechanism of ATP resynthesis is glycolysis. At first, until the glycolysis reaction reaches its maximum rate, the formation of ATP is due to creatine phosphate, and at the end, tissue respiration is included in the process. Work in this zone is characterized by a high oxygen debt - 20-22 liters. Examples of physical activity in this power zone are mid-distance running, mid-distance swimming, track cycling, sprint speed skating, etc. Such loads are called lactate.
Work in the zone high powerhas a maximum duration of up to 30 minutes. For work in this zone, the same contribution of glycolysis and tissue respiration is characteristic. The creatine phosphate pathway is involved only at the very beginning of work. Examples of exercises in this zone are 5000 m running, long-distance skating, cross-country skiing, middle-distance swimming, etc.aerobic-anaerobic, or anaerobic-aerobic.
Working in the temperate zone lasting more than 30 minutes occurs predominantly in an aerobic way. This includes marathon running, cross-country track, road cycling, race walking, long-distance cross-country skiing, hiking, etc.
In acyclic and situational sports (martial arts, gymnastic exercises, sports games), the power of the work performed changes many times. For example, among football players, running at a moderate speed (high power zone) alternates with sprint speed running (zone of maximum or submaximal power). At the same time, football players have such segments of the game when the power of work is reduced to moderate.
When preparing athletes, it is necessary to apply training loads that develop the path of ATP resynthesis, which is the leading one in the energy supply of work in the zone of relative power characteristic of this sport.
Topic: BIOCHEMICAL SHIFTS DURING MUSCLE WORK.
1. The main mechanisms of neuro-humoral regulation of muscle activity.
Any physical work is accompanied by changes in the rate of metabolic processes. The necessary restructuring of metabolism during muscle activity occurs under the influence of neuro-humoral regulation.
The following mechanisms of neuro-humoral regulation of muscle activity can be distinguished:
- Muscular work increases the tone of the sympathetic part of the autonomic nervous system, which is responsible for the work of internal organs and muscles.
In the lungs, under the influence of sympathetic impulses, the respiratory rate increases and the bronchi expand. As a result, pulmonary ventilation is increased, which leads to an improved supply of oxygen to the body.
Under the influence of the sympathetic nervous system, the heart rate also increases, which results in an increase in the speed of blood flow and an improvement in the supply of organs, primarily muscles, with oxygen and nutrients.
The sympathetic system increases sweating, thereby improving thermoregulation.
It has a slowing down effect on the functioning of the kidneys and intestines. Under the influence of the sympathetic nervous system, fat is mobilized.
- Hormones play an equally important role in the restructuring of the body during muscle work. In this case, adrenal hormones are of the greatest importance in biochemical restructuring.
The adrenal medulla producescatecholamines - adrenaline and norepinephrine.The release of medullary hormones into the blood occurs with various emotions and stresses. The biological role of these hormones is to create optimal conditions for the performance of muscle work of great power and duration by affecting physiological functions and metabolism.
Once in the blood, catecholamines duplicate the actions of sympathetic impulses. They cause an increase in the respiratory rate, expansion of the bronchi. Under the influence of adrenaline, the heart rate and their strength increase. Under the influence of adrenaline in the body, blood is redistributed in the vascular bed.
In the liver, these hormones cause accelerated breakdown of glycogen. In adipose tissue, catecholamines activate lipases, thereby accelerating the breakdown of fat. In the muscles, they activate the breakdown of glycogen.
Cortical hormones are also actively involved in enhancing muscle work. Their action lies in the fact that they suppress the action of the enzyme hexokinase, thereby contributing to the accumulation of glucose in the blood. Since these hormones do not act on nerve cells, this makes it possible to nourish nerve cells, since glucose is practically the only source of energy for them. Hormones - glucocorticoids - inhibit anabolic processes and, first of all, protein biosynthesis. This makes it possible to use the released ATP molecules for muscle work. In addition, they stimulate the synthesis of glucose from non-carbohydrate substrates.
2. Biochemical changes in skeletal muscles.
When doing physical workdeep changes occur in the muscles, primarily due to the intensity of the processes of ATP resynthesis.
The use of creatine phosphate as an energy source leads to a decrease in its concentration in muscle cells and the accumulation of creatine in them.
In almost any job, muscle glycogen is used to generate ATP. Therefore, its concentration in the muscles decreases, regardless of the nature of the work. When performing intense loads in the muscles, there is a rapid decrease in glycogen stores and the simultaneous formation and accumulation of lactic acid. Due to the accumulation of lactic acid, the acidity inside the muscle cells increases. An increase in lactate content in muscle cells also causes an increase in osmotic pressure in them. An increase in osmotic pressure leads to the fact that water enters the muscle cell from the capillaries and intercellular space, and the muscles swell or, as athletes say, "clog".
Long-term muscular work of low power causes a gradual decrease in the concentration of glycogen in the muscles. In this case, the decomposition occurs aerobically, with the consumption of oxygen. The end products of this breakdown - carbon dioxide and water - are removed from muscle cells into the blood. Therefore, after performing work of moderate power in the muscles, a decrease in glycogen content is found without accumulation of lactate.
Another important change that occurs in working muscles is an increase in the rate of protein breakdown. The breakdown of proteins is especially accelerated when performing strength exercises, and this affects primarily the contractile proteins of myofibrils. Due to the breakdown of proteins in muscle cells, the content of free amino acids and their decay products - keto acids and ammonia - increases.
Another characteristic change caused by muscle activity is a decrease in the activity of enzymes in muscle cells. One of the reasons for the decrease in enzymatic activity may be increased acidity caused by the appearance of lactic acid in the muscles.
Finally, muscle activity can lead to damage to intracellular structures - myofibrils, mitochondria and other biomembranes. So the violation of the membranes of the sarcoplasmic chain leads to a violation of the conduction of the nerve impulse to the cisterns containing calcium ions. Violation of the integrity of the sarcolemma is accompanied by muscle loss of many important substances that leave the damaged cell in the lymph and blood. The work of enzymes built into membranes is also disrupted. The work of the calcium pump and tissue respiration enzymes located on the inner surface of mitochondrial membranes is disrupted.
3. Biochemical changes in the brain and myocardium.
Brain. During muscle activityin the motor neurons of the cerebral cortex, the formation and subsequent transmission of a motor nerve impulse occurs. Both of these processes (the formation and transmission of a nerve impulse) are carried out with the consumption of energy in the form of ATP molecules. The formation of ATP in nerve cells occurs aerobically. Therefore, during muscular work, the brain's consumption of oxygen from the flowing blood increases. Another feature of the energy metabolism in neurons is that the main oxidation substrate is glucose supplied with the blood stream.
In connection with this specificity of the energy supply of nerve cells, any violation of the supply of the brain with oxygen or glucose inevitably leads to a decrease in its functional activity, which in athletes can manifest itself in the form of dizziness or fainting.
Myocardium. During muscular activity, an increase and an increase in heart rate occurs, which requires a large amount of energy compared to the state of rest. However, the energy supply to the heart muscle is carried out mainly due to aerobic resynthesis of ATP. Only at a heart rate of more than 200 beats / min, anaerobic ATP synthesis is turned on.
The great possibilities of aerobic energy supply in the myocardium are due to the peculiarity of the structure of this muscle. In contrast to skeletal muscles, the myocardium has a more developed and dense network of capillaries, which makes it possible to extract more oxygen and oxidation substrates from the blood. In addition, the cells of the heart muscle have more mitochondria containing tissue respiration enzymes. Heart muscle cells use glucose, fatty acids, ketone bodies, and glycerin as energy sources. Myocardium stores glycogen for a "rainy day" when other sources of energy are depleted.
During intensive work accompanied by an increase in the concentration of lactate in the blood, the myocardium extracts lactate from the blood and oxidizes it to carbon dioxide and water.
When one molecule of lactic acid is oxidized, up to 18 ATP molecules are synthesized. The ability of the myocardium to oxidize lactate is of great biological importance. This enables the body to maintain the required concentration of glucose in the blood for a longer time, which is very important for the bioenergetics of nerve cells, for which glucose is almost the only substrate for oxidation. The oxidation of lactate in the myocardium also contributes to the normalization of the acid-base balance, since the concentration of this acid in the blood decreases.
4. Biochemical changes in the liver.
Muscular activity activates the functions of the liver, aimed mainly at improving the supply of working muscles with extramuscular energy sources carried by the blood. The most important ones are described below.biochemical processes in the liver during work.
1. Under the influence of adrenaline, the rate of glycogen breakdown increases with the formation of free glucose. The resulting glucose is released from the liver cells into the blood, which leads to an increase in its concentration in the blood. At the same time, the content of glycogen decreases. The highest rate of glycogen breakdown is observed in the liver at the beginning of work, when glycogen stores are still large.
2. During physical exercise, liver cells actively extract fat, fatty acids from the blood, the content of which in the blood increases due to the mobilization of fat from fat stores. The fat entering the liver cells is immediately hydrolyzed and converted into glycerol and fatty acids. Further, fatty acids are cleaved by β-oxidation to acetyl coenzyme A, from which ketone bodies are then formed. Ketone bodies are an important source of energy. With the blood stream, they are transferred from the liver to the working organs - the myocardium and skeletal muscles. In these organs, ketone bodies are again converted into acetyl coenzyme A, which is immediately aerobically oxidized in the tricarboxylic acid cycle to carbon dioxide and water, releasing a large amount of energy.
3. Another biochemical process in the liver during muscle work is the formation of glucose from glycerin, amino acids, lactate. This process takes place with the expenditure of energy of ATP molecules. Typically, this synthesis of glucose occurs with prolonged work, leading to a decrease in the concentration of glucose in the bloodstream. Thanks to this process, the body manages to maintain the required level of glucose in the blood.
4. During physical work, the breakdown of muscle proteins increases, leading to the formation of free amino acids, which are further deaminated, releasing ammonia. Ammonia is a cellular poison; it is detoxified in the liver, where it is converted into urea. The synthesis of urea requires a significant amount of energy. With exhausting loads that do not correspond to the functional state of the body, the liver may not be able to cope with the neutralization of ammonia, in this case, the body becomes intoxicated with this poison, leading to a decrease in efficiency.
5. Biochemical changes in the blood.
Changes in the chemical composition of blood is a reflection of those biochemical shifts that occur during muscle activity in various internal organs, skeletal muscles and myocardium.
Biochemical changes occurring in the blood largely depend on the nature of the work, therefore, their analysis should be carried out taking into account the power and duration of physical activity.
When performing muscle work, the following changes are most often found in the blood.
1. Changes in the concentration of proteins in blood plasma. There are two reasons for this. First, increased sweating leads to a decrease in the water content in the blood plasma and, consequently, to its thickening. This causes an increase in the concentration of substances contained in the plasma. Secondly, due to damage to cell membranes, the release of intracellular proteins into the blood plasma is observed. In this case, part of the proteins in the bloodstream passes into the urine, and the other part is used as energy sources.
2. The change in the concentration of glucose in the blood during work goes through a number of phases. At the very beginning of work, the glucose level rises. Glucose is released from the liver, where it is formed from glycogen. In addition, muscles that have glycogen stores do not urgently need glucose from the blood at this stage. But then the stage comes when glycogen in the liver and muscles ends. Then comes the next phase when blood glucose is used to extract energy. Well, at the end of the work, a phase of exhaustion begins and, as a result, hypoglycemia - a decrease in the concentration of glucose in the blood.
3. An increase in the concentration of lactate in the blood is observed in almost any sports activity, but the degree of accumulation of lactate largely depends on the nature of the work performed and the fitness of the athlete. The greatest rise in the level of lactic acid in the blood is observed during physical activity in the submaximal power zone. Since in this case the main source of energy for working muscles is anaerobic glycolysis, which leads to the formation and accumulation of lactate.
It should be remembered that the accumulation of lactate does not occur immediately, but a few minutes after the end of the work. Therefore, the measurement of the lactate level should be carried out 5-7 minutes after the end of the work. If the level of lactate at rest does not exceed 1 - 2 mmol / L, then in highly trained athletes after training, it can reach 20 - 30 mmol / L.
4. Hydrogen indicator (pH). When performing exercises of submaximal power, the pH level can drop quite significantly (by 0.5 units).
5. Exercise is accompanied by an increase in the concentration of free fatty acids and ketone bodies in the blood. This is due to the mobilization of fat in the liver and the release of the products of this process into the blood.
6. Urea. With short-term work, the concentration of urea in the blood changes slightly, with prolonged work, the level of urea increases several times. This is due to increased protein metabolism during exercise.
6. Biochemical changes in urine.
Exercise affects the physicochemical properties of urine, changes in which are explained by significant changes in the chemical composition of urine.
Substances appear in the urine that are usually absent in it. These substances are calledpathological components.The following pathological components are observed in athletes after strenuous work.
1. Protein. Usually, there is no more than 100 mg of protein in the urine. There is a significant excretion of protein in the urine after exercise. This phenomenon is called proteinuria. The heavier the load, the higher the protein content... The cause of this phenomenon is possibly damage to the renal membranes.However, reducing the load completely restores the normal composition of urine.
2. Glucose. At rest, glucose is absent in urine. After completing a workout, glucose is often found in the urine. There are two main reasons for this. First, excess blood glucose during physical work. Secondly, the violation of the renal membranes causes a violation of the process of reabsorption.
3. Ketone bodies. Before work, ketone bodies are not detected in urine. After exertion, ketone bodies can be excreted in the urine in large quantities. This phenomenon is called ketonuria. It is associated with an increase in the concentration of ketone bodies in the blood and an increase in their reabsorption by the kidneys.
4. Lactate. The appearance of lactic acid in the urine is usually seen after exercise that includes submaximal power exercise. By the excretion of lactate in the urine, one can judge the total contribution of glycolysis to the energy supply of all the work performed by an athlete during training.
Along with the effect on the chemical composition of urine, physical activity also changes the physicochemical properties of urine.
Density. Post-workout urine volume tends to be less because most of the water is lost in sweat. This affects the density of the urine, which increases. An increase in urine density is also associated with the appearance of substances in it that are usually absent in urine.
Acidity. Ketone bodies and lactic acid excreted in urine alter urine acidity. Usually urine pH is 5-6 units. After work, it can drop to 4 - 4.5 units.
The more intense the physical activity, the moremore significant changes observed in the composition of urine and blood.
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Topic:ENERGY SUPPLYMUSCLE ACTIVITY
2. Aerobic pathway of ATP resynthesis.
3. Anaerobic pathways for ATP resynthesis.
4. Relationships between different pathways of ATP resynthesis during muscle work. Areas of relative power of muscle work.
Topic: BIOCHEMICAL CHANGES IN THE BODY DURING THE WORK OF DIFFERENT HARACTER
1. The main mechanisms of neuro-humoral regulation of muscle activity.
2. Biochemical changes in skeletal muscles.
3. Biochemical changes in the brain and myocardium.
4. Biochemical changes in the liver.
5. Biochemical changes in the blood.
6. Biochemical changes in urine.
1. Quantitative criteria for the pathways of ATP resynthesis.
Muscle contraction and relaxation require energy, which is generated by hydrolysis of ATP molecules.
However, the reserves of ATP in the muscle are insignificant, they are enough for the muscle to work for 2 seconds. The formation of ATP in the muscles is called ATP resynthesis.
Thus, there are two parallel processes in the muscles - ATP hydrolysis and ATP resynthesis.
ATP resynthesis, unlike hydrolysis, can proceed in different ways, and in total, depending on the energy source, they are distinguished by three: aerobic (basic), creatine phosphate and lactate.
Several criteria are commonly used to quantitatively characterize the various pathways of ATP resynthesis.
1. Maximum power or maximum speed - this is the largest amount of ATP that can be formed per unit of time due to a given resynthesis pathway. The maximum power is measured in calories or joules, assuming that one mmol of ATP corresponds to physiological conditions of about 12 calories or 50 J. Therefore, this criterion has the dimension of cal / min-kg of muscle tissue or J / min-kg of muscle tissue.
2. Deployment time- this is the minimum time required for the ATP resynthesis to reach its highest rate, that is, to achieve maximum power. This criterion is measured in units of time.
3. Time of maintaining or maintaining maximum power - this is the longest time for the functioning of this pathway of ATP resynthesis with maximum power.
4. Metabolic capacity - it is the total amount of ATP that can be produced during muscle work due to this pathway of ATP resynthesis.
Depending on the oxygen consumption, the resynthesis pathways are divided into aerobic and anaerobic.
2. Aerobic pathway of ATP resynthesis
The aerobic pathway of ATP resynthesis is called tissue respiration - it is the main mode of ATP formation in the mitochondria of muscle cells. In the course of tissue respiration, two hydrogen atoms are taken away from the oxidized substance and are transferred along the respiratory chain to molecular oxygen delivered to the muscles by blood, resulting in water. Due to the energy released during the formation of water, ATP molecules are synthesized from ADP and phosphoric acid. Usually, for each water molecule formed, there is a synthesis of three ATP molecules.
Most often, hydrogen is subtracted from the intermediate products of the tricarboxylic acid cycle (TCA). TCA is the final stage of catabolism, during which acetyl coenzyme A is oxidized to carbon dioxide and water. During this process, four pairs of hydrogen atoms are subtracted from the acids listed above, and therefore 12 ATP molecules are formed during the oxidation of one molecule of acetyl coenzyme A.
In turn, acetyl coenzyme A can be formed from carbohydrates, fats, amino acids, that is, through this compound, carbohydrates, fats and amino acids are involved in the TCA.
The rate of aerobic metabolism of ATP is controlled by the content of ADP in muscle cells, which is an activator of tissue respiration enzymes. During muscular work, the accumulation of ADP occurs. Excess ADP accelerates tissue respiration, and it can reach its maximum intensity.
Another activator of ATP resynthesis is carbon dioxide. An excess of this gas in the blood activates the respiratory center in the brain, which ultimately leads to an increase in the speed of blood circulation and an improvement in the supply of oxygen to the muscle.
Maximum power the aerobic pathway is 350-450 cal / min-kg. Compared to the anaerobic pathways of ATP resynthesis, tissue respiration has lower rates, which is limited by the rate of oxygen delivery to the muscles. Therefore, due to the aerobic pathway of ATP resynthesis, only physical activity of moderate power can be carried out.
Deployment time is 3-4 minutes, but for well-trained athletes it can be 1 minute. This is due to the fact that the delivery of oxygen to mitochondria requires restructuring of almost all body systems.
Runtime at maximum power is tens of minutes. This makes it possible to use this path for prolonged muscle work.
Compared to other ATP resynthesis processes occurring in muscle cells, the aerobic pathway has a number of advantages.
1. Economical: 39 ATP molecules are formed from one glycogen molecule, with anaerobic glycolysis only 3 molecules.
2. Versatility Various substances act as initial substrates: carbohydrates, fatty acids, ketone bodies, amino acids.
3. Very long duration of work. At rest, the rate of aerobic resynthesis of ATP may be low, but with physical exertion, it can become maximum.
However, there are also disadvantages.
1. Obligatory oxygen consumption, which is limited by the rate of oxygen delivery to the muscles and the rate of oxygen penetration through the mitochondrial membrane.
2. Long deployment time.
3. Low power in maximum value.
Therefore, the muscle activity inherent in most sports cannot be fully obtained by this way of ATP resynthesis.
In sports practice, the following indicators are used to assess aerobic resynthesis: maximum oxygen consumption (MOC), aerobic metabolism threshold (PAO), anaerobic metabolism threshold (TANM) and oxygen intake.
IPC - it is the maximum possible rate of oxygen consumption by the body during physical work. The higher the VO2 max, the higher the rate of tissue respiration. The more trained the person, the higher the VO2 max. The BMD is usually calculated per 1 kg of body weight. In people who are not involved in sports, the IPC is 50 ml / min-kg, and in trained people it reaches 90 ml / min-kg.
In sports practice, VO2 max is also used to characterize the relative power of aerobic work, which is expressed as a percentage of VO2 max. For example, the relative power of work performed with an oxygen consumption of 3 L / min by an athlete with an IPC of 6 L / min will be 50% of the IPC level.
PAO Is the highest relative power of work, measured by oxygen consumption as a percentage in relation to the IPC. Large PAO values indicate a better development of aerobic resynthesis.
ANSP - it is the minimum relative power of operation, also measured as a percentage of oxygen consumption in relation to the IPC. A high TANM indicates that aerobic resynthesis is higher per unit time, therefore, glycolysis is activated at much higher loads.
Oxygen coming - this is the amount of oxygen (above the working level) used during the execution of a given load to ensure aerobic resynthesis of ATP. Oxygen supply characterizes the contribution of tissue respiration to the energy supply of all the work done. Oxygen supply is often used to assess all aerobic work done.
Under the influence of systematic training in muscle cells, the number of mitochondria increases, the oxygen-transport function of the body improves, the amount of myoglobin in muscles and hemoglobin in the blood increases.
