Anabolism and catabolism are basic concepts. What is anabolism and catabolism What is anabolism

ANABOLISM ANABOLISM

(from the Greek anabole - rise), assimilation, a set of chemicals. processes in a living organism aimed at the formation and renewal of the structural parts of cells and tissues. The opposite of catabolism (dissimilation), it involves the synthesis of complex molecules from simpler ones with the accumulation of energy. The energy required for biosynthesis (mainly in the form of ATP) is supplied catabolically. biological oxidation reactions (see BIOLOGICAL OXIDATION). A. occurs very intensively during periods of growth: in animals - in at a young age, in plants - during the growing season. period. The most important process of A., which has planetary significance, is photosynthesis.

.(Source: “Biological Encyclopedic Dictionary.” Editor-in-chief M. S. Gilyarov; Editorial Board: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin and others - 2nd ed., corrected . - M.: Sov. Encyclopedia, 1986.)

(assimilation), biochemical reactions, as a result of which more simple substances more complex ones are synthesized, which leads to energy storage, the formation of new materials for building cells and growth. Being a process opposite catabolism, occurs simultaneously with it (the first stage of anabolism is the last stage of catabolism, and vice versa). Thus, anabolism and catabolism should be considered inextricably linked with each other, as two sides of the same process - metabolism (see. Metabolism).

.(Source: “Biology. Modern illustrated encyclopedia.” Chief editor A. P. Gorkin; M.: Rosman, 2006.)

See what "ANABOLISM" is in other dictionaries:

Update Dictionary of Russian synonyms. anabolism noun, number of synonyms: 1 update (21) ASIS Dictionary of Synonyms. V.N. Trishin... Dictionary of synonyms

- (from the Greek anabole rise) (assimilation) a set of chemical processes in a living organism aimed at the formation and renewal of the structural parts of cells and tissues. It constitutes the opposite side of catabolism and consists of... ... Big Encyclopedic Dictionary

ANABOLISM, see METABOLISM... Scientific and technical encyclopedic dictionary

A set of reactions that ensure the cell’s biosynthesis of complex compounds (proteins, nucleic acids, polysaccharides, and other polymers) from corresponding low-molecular compounds. A process opposite to catabolism. Necessary for A.... ... Dictionary of microbiology

See Art. Assimilation. Ecological encyclopedic dictionary. Chisinau: Main editorial office of the Moldavian Soviet Encyclopedia. I.I. Dedu. 1989 ... Ecological dictionary

anabolism- a, m. anabolisme m. gr. anabole rise. A set of metabolic reactions in the body corresponding to assimilation and aimed at the formation of complex organic substances (opposite catabolism). SIS 1954. Anabolic aya, oh. All… … Historical Dictionary of Gallicisms of the Russian Language

anabolism- – a set of reactions aimed at the synthesis and renewal of structural and functional components of cells... Brief dictionary biochemical terms

ANABOLISM- (from the Greek anabole rise), the anabolic phase of metabolism, anabolic processes, assimilation processes in the broadest sense of the word, leading to the construction of the cell body, to the creation of living matter. A. includes, first of all, all processes... ... Great Medical Encyclopedia

anabolism- The process of synthesis of organic substances from inorganic ones with the expenditure of energy in living organisms Topics of biotechnology EN anabolism ... Technical Translator's Guide

Anabolism- * anabalism * anabolism metabolic synthesis of complex molecules from simpler precursors. Typically requires energy expenditure and specific anabolic enzymes... Genetics. Encyclopedic Dictionary

And metabolism is the basis of all vital processes of the body:

• the transformation of energy and substances in a living organism, which allows cells to grow, develop and maintain their structure;
• exchange of energy and substances between the body itself and environment.

The rate of metabolic reactions is influenced by the following factors:

• floor: basic metabolic processes in men are 10–20% higher than in women;
• age: from 25 to 30 years old, the rate of metabolic processes decreases by an average of 3%, this happens every ten years;
• weight: the higher the total mass internal organs, muscles and bones, the higher the catabolism will be;
Regular exercise speeds up metabolism - in the first two to three hours by an average of 30%, then during the day - by 5%.

Processes of anabolism and catabolism

Anabolism(plastic metabolism) is the process of creating new cells and their structures, organic substances and tissues of the body, accompanied by the absorption of energy.

This process contributes to:

• development and growth of new tissues, including muscles;
• renewal and restoration of biological structures (cells, tissues);
• bone mineralization.

Anabolism processes occur at rest and under the influence of anabolic hormones (insulin, growth hormone, steroids), as well as substances with anabolic activity (amino acids, proteins, etc.).

Clinical examples of anabolism - nail growth, muscle mass, healing of bone cracks.

Catabolism(energy metabolism) - the process of breakdown opposite to anabolism complex substances, structures of cells, organs and tissues to simple substances.

The stages of catabolism occur with the production of energy in the form of ATP. Thus, the most important function of catabolism is to provide the body with the necessary energy from food and the further use of this energy for the needs of the body.

Catabolism is provoked by:

• fasting and other situations accompanied by an increase in adrenaline concentration;

Stages of catabolism

1. Large molecules (proteins, fats and carbohydrates) are broken down into simple molecules. This process occurs in gastrointestinal tract, outside the cage.
2. In the second stage, simple molecules enter the cell and energy production begins.
3. The third stage is respiration (with the participation of oxygen), it ends with the formation of carbon dioxide, water and large quantity energy.

A clinical example of catabolism is fat burning - weight loss.

The processes of anabolism and catabolism in the body can be in two states: equilibrium or temporary dominance over each other.

The predominance of the anabolic process contributes to the accumulation of mass and tissue growth, and the catabolic process contributes to the destruction of tissue structures and the formation of energy.

The ratio of equilibrium or disequilibrium of anabolism and catabolism depends on age:

• In children, anabolic processes predominate;
• In adults, both processes are in balance, but their ratio may vary depending on the state of health, physical and psycho-emotional stress;
• In the elderly, the process of catabolism predominates.

The relationship between anabolism and catabolism

Anabolism and catabolism are two completely opposite processes, but despite this, they are closely interrelated.

As a result of catabolic reactions, substances and energy are formed that are used in the anabolic process. And anabolism supplies enzymes and substances necessary for catabolism.

So, for example, the human body can meet its need for 14 amino acids. An imbalance of these processes can lead to the death of the body.

Let's figure out how it differs from other supplements.

Learn. It's not as difficult as it seems.

What to do to get rid of beer belly? First read this: . All about nutrition and proper exercise.

Anabolism and catabolism in sports

Physical activity - training - is severe stress for the body. And as we wrote above, this is what is needed to trigger the catabolic reaction. Training forces the body to look for energy not only in fats, which we are trying hard to burn, but also in proteins.

The result of this catabolic reaction is not only weight loss, but also loss of muscle mass as a result of muscle catabolism, which is terrible for the athlete.

Therefore, in sports, protein catabolism is of great importance, in which muscle protein is broken down into amino acids. The main task of the athlete is to weaken protein catabolism and trigger anabolism. The nutrition of bodybuilders, athletes, and complexes is based on this principle. sports supplements, rest mode.

Ways to change metabolism towards the predominance of anabolic processes:

Diet– increase the consumption of protein foods. The more protein, the more building material for cells and muscles. It is worth noting that protein will not be as useful if the food is low in calories, because... the body will lack energy. Everything must be balanced.

You can use amino acid supplements in your diet, they are absorbed faster than protein products, because no time is wasted on digesting them. As a result, muscle cells receive building material faster and, accordingly, recover faster and increase in volume.

Suppress catabolism- not an easy task, but doable: know when to stop your workouts (you can even reduce them to 30 minutes), sleep a lot, don’t skip meals, avoid stress and overwork.

Accelerate anabolism with doping– a special set of hormones, which is not recommended, because it is prohibited and harmful to the body (leads to hormonal imbalance).

The dynamic balance of anabolism with catabolism ensures proper metabolism and wellness. Be healthy!

Content

The human body has the amazing ability to maintain strong connections with the environment, which is carried out through metabolism - a set of processes also called metabolism (it includes anabolism and catabolism). Both components are different from each other and play equally important roles in maintaining the functioning of the body.

Metabolism concept

Metabolism can be defined as a set of biochemical processes occurring in any living organism, including the human body. Metabolism is needed to ensure the vital functions of organs and systems, and these chemical reactions allow us to grow, adapt to environmental conditions, heal wounds, reproduce, etc. Exchange processes are divided into two types:

• assimilation (constructive processes or anabolism);
• dissimilation (destructive processes or catabolism).

What is anabolism

Plastic exchange is possible only if there is a sufficient amount of energy. Anabolism is the process of formation of new cells, structures, tissues, organic substances in the body. The creation of particles is accompanied by the absorption of energy, while all processes occur at rest and are stimulated by anabolic hormones (steroids, insulin, growth hormone, etc.) Anabolism contributes to:

• muscle growth/development;
• bone mineralization;
• restoration of tissues and cells.

What is catabolism

The stages of this process are carried out with the formation of energy (at the same time, ATP synthesis occurs in the ETC - the electron transport chain). Catabolism is energy exchange, the opposite of anabolism, which is characterized by the breakdown of tissues, organ structures, and complex substances into simple elements. The most important task of the process is to provide the body with the necessary energy and further use it for the needs of the body. Catabolism is caused by:

• stress;
• starvation;
• physical activity, other factors that are accompanied by the production of adrenaline.

The relationship between anabolism and catabolism

Both processes are interrelated and equally important for humans; they underlie metabolism. At the same time, energy metabolism serves as the basis for any biochemistry occurring in the body. Every life process will be impossible without metabolism: thanks to the transformation of energy and substances in the body, cells can grow, maintain their structure and develop, creating complex structures.

The relationship between anabolism and catabolism is undeniable, although the two processes are radically opposite to each other. As a result of catabolic reactions, energy and substances are produced that are necessary for the anabolic process. At the same time, anabolism ensures the production of enzymes and other products necessary for catabolism. For example, human body can independently compensate for the lack of fourteen amino acids (constituent components of proteins). An imbalance of metabolic processes can lead to the death of the entire organism.

What happens during catabolism

With the help of energy exchange, the body obtains energy through the destruction of biological materials. During catabolism, the process of breaking down large complexes of molecules into smaller ones occurs, and the energy that is needed for the healthy functioning of organs and systems occurs. Thanks to catabolism, the body receives strength for any physical activity– from the cellular level to the movement of the entire body. During catabolic reactions, large polymers are broken down into simple monomers - the building units from which they are formed. Example of catabolism:

1. There is a violation of the integrity of nucleic acids responsible for the transmission of genetic information, as a result of which they break down into nucleotides. Nucleic acids divided into pentose, purines, and pyrimidines.
2. Polysaccharides are converted into monosaccharides through the process of catabolism. Substances (complex carbohydrates) such as cellulose, starch or glycogen belong to the group of polysaccharides. If they are destroyed, the body will receive simple or fast carbohydrates - ribose, glucose, fructose (a group of substances called monosaccharides).
3. When proteins break down, amino acids are released. These substances, formed as a result of catabolism, can be reused in anabolic reactions, converted into other chemical compounds, or participate in the synthesis of other amino acids. Sometimes proteins break down into amino acids necessary for the synthesis of glucose that enters the blood.

Stages of catabolism

This process is necessary for the body to receive sufficient energy. Any substances processed in the human body are sources of ATP - special molecules necessary for energy storage. The amount of adenosine triphosphate is limited, so it must be constantly replenished and this can only be done through catabolism. Energy exchange occurs in several stages. Stages of catabolism:

• carbohydrates, proteins, fats break down into simple molecules in the gastrointestinal tract, outside the cell;
• molecules enter the cell, resulting in energy accumulation (oxygen-free stage);
• The catabolic processes are completed with the formation of carbon dioxide, large amounts of energy and water.

What happens during the process of anabolism

During energy exchange, matter is created and energy is consumed. As a result of anabolic reactions, complex substances are created. During anabolism, new cells are created and homeostasis of all living tissues of the body is maintained. The body's action is aimed at creating more complex molecules from simple units. The mechanism of anabolic reactions is characterized by the use of several simple substances to synthesize many different end products. Examples of anabolic effects are:

• nutrition of bone tissue for their growth, restoration, development;
• increase in muscle mass;
• wound healing;
• growth of nails, hair, etc.

Due to anabolic processes, monomers are converted into polymers - large molecules that have complex structure, including many miniature building units similar to each other. For example: amino acids (monomers) as a result of a number of anabolic chemical reactions form proteins, which are large complex molecules with a three-dimensional structure (polymers).

The meaning of anabolism and catabolism

Energy metabolic reactions play a very important role important role for humans, while the body can maintain its normal state only if anabolism and catabolism are in balance. When one of the biological processes is suppressed, a violation of the second is inevitable, since they are closely related. An imbalance in energy metabolism can cause various diseases, hormonal disruptions and, as a result, a strong gain of fat, or the reverse process will start and excessive weight loss will occur.

Catabolism is responsible for breaking down muscle tissue and other elements to produce energy. The reaction is triggered during stress, bad sleep, sports training, fatigue, hunger. At the same time, the body produces the hormone cortisol, which destroys muscles, thereby activating the accumulation of fat and increasing glucose levels. These phenomena are extremely undesirable for athletes. However, cortisol also has a positive effect on the body: it breaks down muscle amino acids, which is extremely important for human life.

The importance of anabolism and catabolism for human life cannot be overestimated. If you try to artificially suppress catabolic reactions, hormonal imbalances are likely to develop, so you should learn to adhere to the correct daily routine and control muscle development. This can be achieved if you provide your body with proper rest, healthy image life, choose a balanced diet and competently create a training program. In addition, experts advise athletes to use dietary supplements and vitamins.

How to increase anabolism

Only with a balance of anabolism and catabolism will proper metabolism and a healthy state of a person be ensured. Excessive predominance of one process over another becomes the cause of development various pathologies, so you should consult your doctor before deciding to increase anabolism. You can make the energy exchange rate high in the following ways:

1. Diet. An increase in the amount of protein consumed leads to a natural increase in the volume of building materials for muscles. However, excess protein will not be as beneficial if you eat low-calorie foods, since the body will not have enough energy to absorb it. Nutrition must be balanced, then the cells will receive the necessary building material faster and muscle tissue will begin to grow.
2. Dream. Adequate rest is very important for anabolism, especially if a person was involved in sports that day.
3. Diet. Without the timely supply of nutrients to the body, the process of tissue growth is impossible.
4. Mental stability. To reduce the rate of catabolic reactions, it is important to avoid stressful situations.
5. Taking doping drugs. This measure is extremely undesirable for accelerating anabolism, since it often leads to problems at the hormonal level and other pathologies.

Anabolism and catabolism in sports

Because physical activity are a serious stress for the body, they trigger catabolic processes. Training creates the need to look for additional sources of energy (the body takes them not only from fat deposits, but also from proteins - the building blocks of muscles). What is muscle catabolism? This is a natural process in which the energy required for physical effort is produced through the breakdown of muscle tissue.

Anabolism and catabolism in sports is always a hot topic, since it is important for athletes to maintain maximum or even increase muscle volume. One of the main tasks of a person of any age who is actively involved in sports is to weaken the catabolic reactions of proteins and activate the anabolic process. A bodybuilder can balance anabolism and catabolism with the help of proper nutrition, maintaining a rest regime and taking sports supplements (protein, etc.).

Video: What are anabolism and catabolism

Attention! The information presented in the article is for informational purposes only. The materials in the article do not encourage self-treatment. Only a qualified doctor can make a diagnosis and make treatment recommendations based on individual characteristics specific patient.

Anabolism and catabolism are the main metabolic processes.

Catabolism is the enzymatic breakdown of complex organic compounds, carried out inside the cell due to oxidation reactions. Catabolism is accompanied by the release of energy and its storage in high-energy phosphate bonds of ATP.

Anabolism is the synthesis of complex organic compounds - proteins, nucleic acids, polysaccharides - from simple precursors that enter the cell from the environment or are formed during the process of catabolism. Synthesis processes are associated with the consumption of free energy, which is supplied by ATP (Fig. 31).

Rice. 31 Scheme of metabolic pathways in a bacterial cell

Depending on the biochemistry of the dissimilation process (catabolism), respiration and fermentation are distinguished.

Breath is a complex process of biological oxidation of various compounds) associated with the formation of a large amount of energy accumulated in the form of high-energy bonds in the structure of ATP (adenosine triphosphate), UTP (uridine triphosphate), etc., and the formation of carbon dioxide and water. There are aerobic and anaerobic respiration.

Fermentation– incomplete decomposition of organic compounds with the formation of a small amount of energy and energy-rich products.

Anabolism involves synthesis processes that use the energy produced by catabolism. In a living cell, the processes of catabolism and anabolism occur simultaneously and continuously. Many reactions and intermediate products are common to them.

Living organisms are classified according to the energy or carbon source they use. Carbon is the main element of living matter. It plays a leading role in constructive metabolism.

Depending on the source of cellular carbon, all organisms, including prokaryotes, are divided into autotrophs and heterotrophs.

Autotrophs use CO 2 as the only source of carbon, reducing it with hydrogen, which is split off from water or other substances. They synthesize organic substances from simple inorganic compounds in the process of photo- or chemosynthesis.

Heterotrophs obtain carbon from organic compounds.

Living organisms can use light or chemical energy. Organisms that live off light energy are called phototrophic. They synthesize organic substances by absorbing electromagnetic radiation from the Sun (light). These include plants, blue-green algae, green and purple sulfur bacteria.

Organisms that receive energy from substrates, food sources (energy of oxidation of inorganic substances) are called chemotrophs. TO chemoheterotrophs include most bacteria, as well as fungi and animals.

There is a small group chemoautotrophs. Such chemosynthetic microorganisms include nitrifying bacteria, which, by oxidizing ammonia to nitrous acid, release the energy necessary for synthesis. Chemosynthetics also include hydrogen bacteria that obtain energy through the oxidation of molecular hydrogen.

Carbohydrates as a source of energy

In most organisms, the breakdown of organic substances occurs in the presence of oxygen - aerobic metabolism. As a result of this exchange, energy-poor people remain final products(CO 2 and H 2 O), but a lot of energy is released. The process of aerobic metabolism is called respiration, anaerobic - fermentation.

Carbohydrates are the main energy material that cells use primarily to produce chemical energy. In addition, proteins and fats can also be used during respiration, and alcohols and organic acids during fermentation.

Organisms break down carbohydrates in different ways, in which the most important intermediate product is pyruvic acid (pyruvate). Pyruvate is central to metabolism during respiration and fermentation. There are three main mechanisms for the formation of PVC.

1. Fructose diphosphate (glycolysis) or Embden-Meyerhoff-Parnas pathway- a universal path.

The process begins with phosphorylation (Fig. 32). With the participation of the enzyme hexokinase and ATP, glucose is phosphorylated at the sixth carbon atom to form glucose-6-phosphate. This is the active form of glucose. It serves as the starting product for the breakdown of carbohydrates in any of three ways.

During glycolysis, glucose-6-phosphate is isomerized to fructose-6-phosphate and then phosphorylated at the first carbon atom by the action of 6-phosphofructokinase. The resulting fructose-1,6-biphosphate, under the action of the enzyme aldolase, easily breaks down into two trioses: phosphoglyceraldehyde and dihydroxyacetone phosphate. Further conversion of C 3 -carbohydrates is carried out due to the transfer of hydrogen and phosphorus residues through a number of organic acids with the participation of specific dehydrogenases. All reactions in this pathway, with the exception of three involving hexokinase, 6-phosphofructokinase and pyruvate kinase, are completely reversible. At the stage of formation of pyruvic acid, the anaerobic phase of the transformation of carbohydrates ends.

The maximum amount of energy received by a cell from the oxidation of one carbohydrate molecule by the glycolytic pathway is 2 × 10 5 J.

Fig.32. Fructose diphosphate pathway for the breakdown of glucose

2. Pentose phosphate (Warburg-Dickens-Horecker)path is also characteristic of most organisms (mostly for plants, and for microorganisms it plays an auxiliary role). Unlike glycolysis, the PF pathway does not produce pyruvate.

Glucose-6-phosphate is converted to 6-phosphoglucolactone, which is decarboxylated (Fig. 33). In this case, ribulose-5-phosphate is formed, which completes the oxidation process. Subsequent reactions are considered as processes of conversion of pentose phosphates into hexose phosphates and vice versa, i.e. a cycle is formed. It is believed that the pentose phosphate pathway at one stage passes into glycolysis.

When every six glucose molecules pass through the PF, one molecule of glucose-6-phosphate is completely oxidized to CO 2 and 6 molecules of NADP + are reduced to NADP·H 2 . As a mechanism for obtaining energy, this pathway is two times less efficient than the glycolytic one: for every molecule of glucose, 1 molecule of ATP is formed.

Rice. 33. Pentose phosphate pathway for the breakdown of glucose-6-phosphate

The main purpose of this pathway is to supply pentoses necessary for the synthesis of nucleic acids and ensure the formation of most of the NADPH 2 necessary for the synthesis of fatty acids and steroids.

3. Entner-Doudoroff pathway (ketodeoxyphosphogluconate or KDPG pathway) found only in bacteria. Glucose is phosphorylated by the ATP molecule with the participation of the enzyme hexokinase (Fig. 34).

Fig.34. Entner-Doudoroff pathway for glucose breakdown

The phosphorylation product, glucose-6-phosphate, is dehydrogenated to 6-phosphogluconate. Under the action of the enzyme phosphogluconate dehydrogenase, water is split off from it and 2-keto-3-deoxy-6-phosphogluconate (KDPG) is formed. The latter is cleaved by a specific aldolase into pyruvate and glyceraldehyde-3-phosphate. Glyceraldehyde is further exposed to enzymes in the glycolytic pathway and is transformed into a second molecule of pyruvate. In addition, this pathway supplies the cell with 1 ATP molecule and 2 NADH 2 molecules.

Thus, the main intermediate product of the oxidative breakdown of carbohydrates is pyruvic acid, which, with the participation of enzymes, is converted into various substances. The PVK formed in one of the ways in the cell is subject to further oxidation. The released carbon and hydrogen are removed from the cell. Carbon is released in the form of CO 2, hydrogen is transferred to various acceptors. Moreover, either a hydrogen ion or an electron can be transferred, so the transfer of hydrogen is equivalent to the transfer of an electron. Depending on the final hydrogen acceptor (electron), aerobic respiration, anaerobic respiration and fermentation are distinguished.

Breath

Respiration is a redox process that occurs with the formation of ATP; The role of hydrogen (electron) donors in it is played by organic or inorganic compounds, and in most cases, inorganic compounds serve as hydrogen (electron) acceptors.

If the final electron acceptor is molecular oxygen, the respiratory process is called aerobic respiration. In some microorganisms, the final electron acceptor is compounds such as nitrates, sulfates and carbonates. This process is called anaerobic respiration.

Aerobic respiration– the process of complete oxidation of substrates to CO 2 and H 2 O with the formation of a large amount of energy in the form of ATP.

Complete oxidation of pyruvic acid occurs under aerobic conditions in the tricarboxylic acid cycle (TCA cycle or Krebs cycle) and the respiratory chain.

Aerobic respiration consists of two phases:

1). Pyruvate formed during glycolysis is oxidized to acetyl-CoA and then to CO 2, and the released hydrogen atoms move to acceptors. This is how the TTC is carried out.

2). Hydrogen atoms removed by dehydrogenases are accepted by coenzymes of anaerobic and aerobic dehydrogenases. They are then transported along the respiratory chain, in certain sections of which a significant amount of free energy is formed in the form of high-energy phosphates.

Tricarboxylic acid cycle (Krebs cycle, TCA cycle)

Pyruvate, formed during glycolysis, is decarboxylated to acetaldehyde with the participation of the multienzyme complex pyruvate dehydrogenase. Acetaldehyde, combining with the coenzyme of one of the oxidative enzymes - coenzyme A (CoA-SH), forms “activated acetic acid” - acetyl-CoA - a high-energy compound.

Acetyl-CoA, under the action of citrate synthetase, reacts with oxaloacetic acid (oxaloacetate), forming citric acid (C6 citrate), which is the main link in the TCA cycle (Fig. 35). Citrate after isomerization turns into isocitrate. This is followed by oxidative (elimination of H) decarboxylation (elimination of CO 2) isocitrate, the product of which is 2-oxoglutarate (C 5). Under the influence of the enzyme complex ɑ-ketoglutarate dehydrogenase with the active group NAD, it turns into succinate, losing CO 2 and two hydrogen atoms. The succinate is then oxidized to fumarate (C4), and the latter is hydrated (addition of H2O) to malate. In the final reaction of the Krebs cycle, malate is oxidized, which leads to the regeneration of oxaloacetate (C 4). Oxaloacetate reacts with acetyl-CoA and the cycle repeats. Each of the 10 TCA cycle reactions, with the exception of one, is easily reversible. Two carbon atoms enter the cycle in the form of acetyl-CoA and the same number of carbon atoms leave this cycle in the form of CO 2.

Rice. 35. Krebs cycle (according to V.L. Kretovich):

1, 6 – oxidative decarboxylation system; 2 – citrate synthetase, coenzyme A; 3, 4 – aconitate hydratase; 5 – isocitrate dehydrogenase; 7 – succinate dehydrogenase; 8 – fumarate hydratase; 9 – malate dehydrogenase; 10 – spontaneous transformation; 11 - pyruvate carboxylase

As a result of the four redox reactions of the Krebs cycle, three pairs of electrons are transferred to NAD and one pair of electrons to FAD. The electron carriers NAD and FAD, reduced in this way, are then subjected to oxidation already in the electron transport chain. The cycle produces one ATP molecule, 2 CO 2 molecules and 8 hydrogen atoms.

The biological significance of the Krebs cycle is that it is a powerful supplier of energy and “building blocks” for biosynthetic processes. The Krebs cycle operates only under aerobic conditions; under anaerobic conditions it is open at the level of α-ketoglutarate dehydrogenase.

Respiratory chain

The last stage of catabolism is oxidative phosphorylation. During this process, most of the metabolic energy is released.

The electron carriers NAD and FAD, reduced in the Krebs cycle, are subject to oxidation in the respiratory chain or electron transport chain. The carrier molecules are dehydrogenases, quinones and cytochromes.

Both enzyme systems are located in the plasma membrane in prokaryotes, and in the inner membrane of mitochondria in eukaryotes. Electrons from hydrogen atoms (NAD, FAD) pass through a complex chain of carriers to molecular oxygen, reducing it, and water is formed.

Balance. Calculations of the energy balance showed that when glucose is broken down glycolytically and through the Krebs cycle, followed by oxidation in the respiratory chain to CO 2 and H 2 O, 38 ATP molecules are formed for each glucose molecule. Moreover, the maximum amount of ATP is formed in the respiratory chain - 34 molecules, 2 molecules in the EMT pathway and 2 molecules in the TCA cycle (Fig. 36).

Incomplete oxidation of organic compounds

Respiration is usually associated with complete oxidation of the organic substrate, i.e. the final decomposition products are CO 2 and H 2 O.

However, some bacteria and a number of fungi do not completely oxidize carbohydrates. The end products of incomplete oxidation are organic acids: acetic, citric, fumaric, gluconic, etc., which accumulate in the medium. This oxidative process is used by microorganisms to obtain energy. However, the total energy yield is significantly less than with complete oxidation. Part of the energy of the oxidized initial substrate is stored in the resulting organic acids.

Microorganisms that develop due to the energy of incomplete oxidation are used in the microbiological industry to produce organic acids and amino acids.

You've probably heard such expressions as anabolism, catabolism and metabolism. If these are still unclear words for you, then I will help you figure it out and understand what these terms mean.
In fact, everything is very simple, these terms are used in medicine, biology, biochemistry, etc. It’s just that some authors, when trying to tell something, like to use a lot of special terminology, thereby confusing listeners. They forget they're talking to people different professions, so not everyone understands them.
For example, I always try to tell even very complex things from different sciences in simple and understandable words. Sometimes it's good to make complex things simple
Although, an educated person, of course, should know basic concepts from various sciences...

ANABOLISM is the name given to all processes of creating new substances, cells and tissues of the body.
Examples of anabolism: synthesis of proteins and hormones in the body, creation of new cells, accumulation of fat, creation of new muscle fibers - this is all anabolism. That is, the totality of all processes in the body during which the creation of any new substances and tissues occurs is called anabolism!

CATABOLISM is the opposite of anabolism. That is, this is the breakdown of complex substances into simpler ones, as well as the breakdown of old parts of cells and tissues of the body.
It may seem to you that catabolism is something bad, because it is destruction... In fact, this is not so, because the breakdown of fats and carbohydrates to produce energy is also catabolism, and without this energy the body cannot exist.
Moreover, this energy can be directed to the synthesis of necessary substances, to the creation of cells and renewal of the body, that is, to anabolism. Anabolism and catabolism are interconnected.

You've also probably heard the phrase " anabolic steroid" are illegal drugs that are used by some athletes. The term “anabolic” is not scary, it simply means that these substances are involved in anabolic processes, that is, in the processes of creating new cells and substances. But the danger is that anabolic steroids are hormonal drugs, they interfere with the human hormonal system and destroy it. Violation hormonal balance leads to metabolic disorders, injuries, and serious illnesses, for example, to diseases of the heart, liver and kidneys - this is known to any doctor.
Friends - do clean sports without chemicals, so as not to destroy the body, but to strengthen it!

So, anabolism is the process of synthesis of new substances, catabolism is the process of breakdown of substances.
All together this is called METABOLISM, which means metabolism.
As you can see, anabolism and catabolism are opposite processes, but they are two parts of the same process - metabolism, and both of these parts are important!
The right combination of anabolism and catabolism ensures a balanced metabolism and health of your body.