The use of glucose in human life - chemistry. What are the benefits and harms of glucose?

Glucose means “sweet” in Greek. In nature, it is found in large quantities in the juices of berries and fruits, including grape juice, which is why it is popularly called “wine sugar.”

History of discovery

Glucose was discovered at the beginning of the 19th century by the English physician, chemist and philosopher William Prout. This substance became widely known after Henri Braccono extracted it from sawdust in 1819.

Physical properties

Glucose is a colorless crystalline powder with a sweet taste. It is highly soluble in water, concentrated sulfuric acid, and Schweitzer's reagent.

Molecule structure

Like all monosaccharides, glucose is a heterofunctional compound (the molecule contains several hydroxyl groups and one carboxyl group). In the case of glucose, the carboxyl group is the aldehyde.

The general formula of glucose is C6H12O6. The molecules of this substance have a cyclic structure and two spatial isomers, alpha and beta forms. In the solid state, the alpha form predominates almost 100%. In solution, the beta form is more stable (it occupies approximately 60%). Glucose is the final product of the hydrolysis of all poly- and disaccharides, that is, glucose is obtained in the overwhelming majority of cases in this way.

Obtaining the substance

In nature, glucose is produced in plants as a result of photosynthesis. Let's look at industrial and laboratory methods for producing glucose. In the laboratory, this substance is the result of aldol condensation. In industry, the most common method is to obtain glucose from starch.

Starch is a polysaccharide, the monoparts of which are glucose molecules. That is, to obtain it, it is necessary to decompose the polysaccharide into monoparts. How is this process carried out?

The production of glucose from starch begins with the fact that the starch is placed in a container of water and mixed (starch milk). Bring another container of water to a boil. It is worth noting that there should be twice as much boiling water as starch milk. In order for the reaction to produce glucose to proceed to completion, a catalyst is needed. In this case, it is salt water or the calculated amount is added to a container of boiling water. Then starch milk is slowly poured in. In this process, it is very important not to get a paste; if it does form, you should continue boiling until it disappears completely. On average, boiling takes one and a half hours. In order to be sure that the starch has been completely hydrolyzed, a high-quality reaction must be carried out. Iodine is added to the selected sample. If the liquid turns blue, it means that hydrolysis is not complete, but if it turns brown or red-brown, it means that there is no more starch in the solution. But this solution contains not only glucose; it was produced using a catalyst, which means that there is also acid. How to remove acid? The answer is simple: using neutralization with clean chalk and finely crushed porcelain.

Neutralization is checked. Next, the resulting solution is filtered. There's just one thing to do: the resulting colorless liquid should be evaporated. The formed crystals are our final result. Now consider the production of glucose from starch (reaction).

Chemical essence of the process

This equation for the production of glucose is presented before the intermediate product - maltose. Maltose is a disaccharide consisting of two glucose molecules. It is clearly seen that the methods for producing glucose from starch and maltose are the same. That is, to continue the reaction we can put the following equation.

In conclusion, it is worth summarizing the necessary conditions for the production of glucose from starch to be successful.

The necessary conditions

catalyst (hydrochloric or sulfuric acid);
temperature (at least 100 degrees);
pressure (atmospheric enough, but increasing pressure speeds up the process).

This method is the simplest, with a high yield of the final product and minimal energy costs. But he's not the only one. Glucose is also produced from cellulose.

Derivation from cellulose

The essence of the process is almost completely consistent with the previous reaction.

The production of glucose (formula) from cellulose is given. In reality, this process is much more complicated and energy-consuming. So, the product that enters into the reaction is waste from the wood processing industry, crushed to a fraction with a particle size of 1.1 - 1.6 mm. This product is treated first with acetic acid, then with hydrogen peroxide, then with sulfuric acid at a temperature of at least 110 degrees and a hydromodule of 5. The duration of this process is 3-5 hours. Then, hydrolysis with sulfuric acid takes place over two hours at room temperature and hydromodulus 4-5. Then dilution with water and inversion occurs for approximately one and a half hours.

Quantification methods

Having considered all the methods for obtaining glucose, you should study methods for its quantitative determination. There are situations when only a solution containing glucose should participate in the technological process, that is, the process of evaporating the liquid until crystals are obtained is unnecessary. Then the question arises of how to determine what concentration of a given substance is in solution. The resulting amount of glucose in solution is determined by spectrophotometric, polarimetric and chromatographic methods. There is also a more specific method of determination - enzymatic (using the enzyme glucosidase). In this case, the products of the action of this enzyme are counted.

Application of glucose

In medicine, glucose is used for intoxication (this can be either food poisoning or an infection). In this case, the glucose solution is administered intravenously using a dropper. This means that in pharmacy glucose is a universal antioxidant. This substance also plays an important role in the detection and diagnosis of diabetes. Here glucose acts as a stress test.

Glucose occupies a very important place in the food industry and cooking. Separately, the role of glucose in winemaking, beer and moonshine production should be outlined. We are talking about such a method as producing ethanol. Let us consider this process in detail.

Obtaining alcohol

The technology for producing alcohol has two stages: fermentation and distillation. Fermentation, in turn, is carried out with the help of bacteria. In biotechnology, cultures of microorganisms have long been developed that make it possible to obtain the maximum yield of alcohol in the minimum amount of time spent. In everyday life, ordinary table yeast can be used as reaction assistants.

First of all, glucose is diluted in water. The microorganisms used are diluted in another container. Next, the resulting liquids are mixed, shaken and placed in a container with this tube connected to another (U-shaped). The end of the tube is poured into the middle of the second tube and closed with a rubber stopper with a hollow glass rod having an extended end.

This container is placed in a thermostat at a temperature of 25-27 degrees for four days. A tube containing lime water will appear cloudy, indicating that carbon dioxide has reacted with it. As soon as carbon dioxide ceases to be released, fermentation can be considered complete. Next comes the distillation stage. In the laboratory, reflux condensers are used to distill alcohol - devices in which cold water flows along the outer wall, thereby cooling the resulting gas and turning it back into liquid.

At this stage, the liquid that is in our container should be heated to 85-90 degrees. This way the alcohol will evaporate, but the water will not be brought to a boil.

Mechanism for producing alcohol

Let's consider the production of alcohol from glucose in the reaction equation: C6H12O6 = 2C2H5OH + 2CO2.

So, it can be noted that the mechanism for producing ethanol from glucose is very simple. Moreover, it has been known to mankind for many centuries, and has been brought to almost perfection.

The importance of glucose in human life

So, having a certain understanding of this substance, its physical and chemical properties, and its use in various fields of industry, we can conclude what glucose is. Obtaining it from polysaccharides already makes it clear that, being the main component of all sugars, glucose is an irreplaceable source of energy for humans. As a result of metabolism, adenosine triphosphoric acid is formed from this substance, which is converted into a unit of energy.

But not all the glucose that enters the human body is used to replenish energy. While awake, a person converts only 50 percent of the glucose received into ATP. The rest is converted to glycogen and accumulates in the liver. Glycogen breaks down over time, thereby regulating blood sugar levels. The quantitative content of this substance in the body is a direct indicator of its health. The hormonal functioning of all systems depends on the amount of sugar in the blood. Therefore, it is worth remembering that excessive use of this substance can lead to serious consequences.

At first glance, glucose is a simple and understandable substance. Even from the point of view of chemistry, its molecules have a fairly simple structure, and the chemical properties are understandable and familiar in everyday life. But, despite this, glucose is of great importance both for the person himself and for all areas of his life.

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Ministry of Education and Science of the Russian Federation

Federal State Budgetary Educational Institution of Higher Education

Tambov State University named after G.R. Derzhavina

on the topic: The biological role of glucose in the body

Completed:

Shamsidinov Shokhiyorzhon Fazliddin coals

Tambov 2016

1. Glucose

1.1 Features and functions

2.1 Glucose catabolism

2.4 Glucose synthesis in the liver

2.5 Glucose synthesis from lactate

Literatures used

1. Glucose

1.1 Features and functions

Glucose (from the ancient Greek glkhket sweet) (C 6 H 12 O 6), or grape sugar, or dextrose, is found in the juice of many fruits and berries, including grapes, which is where the name of this type of sugar comes from. It is a monosaccharide and six-hydroxy sugar (hexose). The glucose unit is part of polysaccharides (cellulose, starch, glycogen) and a number of disaccharides (maltose, lactose and sucrose), which, for example, are quickly broken down into glucose and fructose in the digestive tract.

Glucose belongs to the group of hexoses and can exist in the form of b-glucose or b-glucose. The difference between these spatial isomers is that at the first carbon atom of b-glucose the hydroxyl group is located under the plane of the ring, while for b-glucose it is above the plane.

Glucose is a bifunctional compound because contains functional groups - one aldehyde and 5 hydroxyl. Thus, glucose is a polyhydric aldehyde alcohol.

The structural formula of glucose is:

Abbreviated formula

1.2 Chemical properties and structure of glucose

It has been experimentally established that the glucose molecule contains aldehyde and hydroxyl groups. As a result of the interaction of a carbonyl group with one of the hydroxyl groups, glucose can exist in two forms: open chain and cyclic.

In a glucose solution, these forms are in equilibrium with each other.

For example, in an aqueous solution of glucose the following structures exist:

The cyclic b- and c-forms of glucose are spatial isomers that differ in the position of the hemiacetal hydroxyl relative to the plane of the ring. In b-glucose this hydroxyl is in the trans position to the hydroxymethyl group -CH 2 OH, in b-glucose it is in the cis position. Taking into account the spatial structure of the six-membered ring, the formulas of these isomers have the form:

In the solid state, glucose has a cyclic structure. Ordinary crystalline glucose is the b-form. In solution, the b-form is more stable (at steady state, it accounts for more than 60% of the molecules). The proportion of the aldehyde form in equilibrium is insignificant. This explains the lack of interaction with fuchsinous acid (qualitative reaction of aldehydes).

In addition to the phenomenon of tautomerism, glucose is characterized by structural isomerism with ketones (glucose and fructose are structural interclass isomers)

Chemical properties of glucose:

Glucose has chemical properties characteristic of alcohols and aldehydes. In addition, it also has some specific properties.

1. Glucose is a polyhydric alcohol.

Glucose with Cu(OH) 2 gives a blue solution (copper gluconate)

2. Glucose is an aldehyde.

a) Reacts with an ammonia solution of silver oxide to form a silver mirror:

CH 2 OH-(CHOH) 4 -CHO+Ag 2 O > CH 2 OH-(CHOH) 4 -COOH + 2Ag

gluconic acid

b) With copper hydroxide it gives a red precipitate Cu 2 O

CH 2 OH-(CHOH) 4 -CHO + 2Cu(OH) 2 > CH 2 OH-(CHOH) 4 -COOH + Cu 2 Ov + 2H 2 O

gluconic acid

c) Reduced with hydrogen to form hexahydric alcohol (sorbitol)

CH 2 OH-(CHOH) 4 -CHO + H 2 > CH 2 OH-(CHOH) 4 -CH 2 OH

3. Fermentation

a) Alcoholic fermentation (to produce alcoholic beverages)

C 6 H 12 O 6 > 2CH 3 -CH 2 OH + 2CO 2 ^

ethanol

b) Lactic acid fermentation (sour milk, fermentation of vegetables)

C 6 H 12 O 6 > 2CH 3 -CHOH-COOH

lactic acid

1.3 Biological significance of glucose

Glucose is a necessary component of food, one of the main participants in metabolism in the body, it is very nutritious and easily digestible. During its oxidation, more than a third of the energy resource used in the body is released - fats, but the role of fats and glucose in the energy of different organs is different. The heart uses fatty acids as fuel. Skeletal muscles need glucose to “start”, but nerve cells, including brain cells, work only on glucose. Their need is 20-30% of the generated energy. Nerve cells need energy every second, and the body receives glucose when eating. Glucose is easily absorbed by the body, so it is used in medicine as a strengthening remedy. Specific oligosaccharides determine blood type. In confectionery for making marmalade, caramel, gingerbread, etc. Glucose fermentation processes are of great importance. So, for example, when sauerkraut, cucumbers, and milk are pickled, lactic acid fermentation of glucose occurs, as well as when ensiling feed. In practice, alcoholic fermentation of glucose is also used, for example, in the production of beer. Cellulose is the starting material for the production of silk, cotton wool, and paper.

Carbohydrates are indeed the most common organic substances on Earth, without which the existence of living organisms is impossible.

In a living organism, during metabolism, glucose is oxidized, releasing a large amount of energy:

C 6 H 12 O 6 +6O 2 ??? 6CO 2 +6H 2 O+2920kJ

2. Biological role of glucose in the body

Glucose is the main product of photosynthesis and is formed in the Calvin cycle. In the human and animal body, glucose is the main and most universal source of energy for metabolic processes.

2.1 Glucose catabolism

Glucose catabolism is the main supplier of energy for the body's vital processes.

Aerobic breakdown of glucose is its ultimate oxidation to CO 2 and H 2 O. This process, which is the main path of glucose catabolism in aerobic organisms, can be expressed by the following summary equation:

C 6 H 12 O 6 + 6O 2 > 6CO 2 + 6H 2 O + 2820 kJ/mol

Aerobic breakdown of glucose includes several stages:

* aerobic glycolysis is the process of glucose oxidation with the formation of two pyruvate molecules;

* general path of catabolism, including the conversion of pyruvate to acetyl-CoA and its further oxidation in the citrate cycle;

* chain of electron transfer to oxygen, coupled with dehydrogenation reactions occurring during the breakdown of glucose.

In certain situations, oxygen supply to tissues may not meet their needs. For example, in the initial stages of intense muscle work under stress, heart contractions may not reach the desired frequency, and the muscles' oxygen requirements for the aerobic breakdown of glucose are high. In such cases, a process is activated that occurs without oxygen and ends with the formation of lactate from pyruvic acid.

This process is called anaerobic breakdown, or anaerobic glycolysis. Anaerobic breakdown of glucose is energetically ineffective, but this process can become the only source of energy for a muscle cell in the described situation. Later, when the supply of oxygen to the muscles is sufficient as a result of the heart switching to an accelerated rhythm, anaerobic breakdown switches to aerobic.

Aerobic glycolysis is the process of oxidation of glucose to pyruvic acid, which occurs in the presence of oxygen. All enzymes that catalyze the reactions of this process are localized in the cytosol of the cell.

1. Stages of aerobic glycolysis

Aerobic glycolysis can be divided into two stages.

1. Preparatory stage, during which glucose is phosphorylated and split into two phosphotriose molecules. This series of reactions takes place using 2 molecules of ATP.

2. Stage associated with ATP synthesis. Through this series of reactions, phosphotrioses are converted to pyruvate. The energy released at this stage is used to synthesize 10 mol of ATP.

2. Aerobic glycolysis reactions

Conversion of glucose-6-phosphate into 2 molecules of glyceraldehyde-3-phosphate

Glucose-6-phosphate, formed as a result of phosphorylation of glucose with the participation of ATP, is converted into fructose-6-phosphate in the next reaction. This reversible isomerization reaction occurs under the action of the enzyme glucose phosphate isomerase.

Pathways of glucose catabolism. 1 - aerobic glycolysis; 2, 3 - general path of catabolism; 4 - aerobic breakdown of glucose; 5 - anaerobic breakdown of glucose (in the frame); 2 (circled) - stoichiometric coefficient.

Conversion of glucose-6-phosphate to triose phosphates.

Conversion of glyceraldehyde 3-phosphate to 3-phosphoglycerate.

This part of aerobic glycolysis includes reactions associated with ATP synthesis. The most complex reaction in this series of reactions is the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate. This transformation is the first oxidation reaction during glycolysis. The reaction is catalyzed by glyceraldehyde-3-phosphate dehydrogenase, which is an NAD-dependent enzyme. The significance of this reaction lies not only in the fact that a reduced coenzyme is formed, the oxidation of which in the respiratory chain is associated with the synthesis of ATP, but also in the fact that the free energy of oxidation is concentrated in the high-energy bond of the reaction product. Glyceraldehyde-3-phosphate dehydrogenase contains a cysteine residue in the active center, the sulfhydryl group of which is directly involved in catalysis. Oxidation of glyceraldehyde-3-phosphate leads to the reduction of NAD and the formation, with the participation of H 3 PO 4, of a high-energy anhydride bond in 1,3-bisphosphoglycerate at position 1. In the next reaction, the high-energy phosphate is transferred to ADP with the formation of ATP

The formation of ATP in this manner is not associated with the respiratory chain, and is called substrate phosphorylation of ADP. The formed 3-phosphoglycerate no longer contains a high-energy bond. In the following reactions, intramolecular rearrangements occur, the meaning of which is that a low-energy phosphoester is converted into a compound containing a high-energy phosphate. Intramolecular transformations involve the transfer of a phosphate residue from position 3 in phosphoglycerate to position 2. Then, a water molecule is cleaved from the resulting 2-phosphoglycerate with the participation of the enolase enzyme. The name of the dehydrating enzyme is given by the reverse reaction. As a result of the reaction, a substituted enol is formed - phosphoenolpyruvate. The resulting phosphoenolpyruvate is a high-energy compound, the phosphate group of which is transferred in the next reaction to ADP with the participation of pyruvate kinase (the enzyme is also named for the reverse reaction in which phosphorylation of pyruvate occurs, although such a reaction does not take place in this form).

Conversion of 3-phosphoglycerate to pyruvate.

3. Oxidation of cytoplasmic NADH in the mitochondrial respiratory chain. Shuttle systems

NADH, formed by the oxidation of glyceraldehyde-3-phosphate in aerobic glycolysis, undergoes oxidation by transfer of hydrogen atoms to the mitochondrial respiratory chain. However, cytosolic NADH is unable to transfer hydrogen to the respiratory chain because the mitochondrial membrane is impermeable to it. Hydrogen transfer through the membrane occurs using special systems called "shuttle". In these systems, hydrogen is transported across the membrane with the participation of pairs of substrates bound by corresponding dehydrogenases, i.e. There is a specific dehydrogenase on both sides of the mitochondrial membrane. There are 2 known shuttle systems. In the first of these systems, hydrogen from NADH in the cytosol is transferred to dihydroxyacetone phosphate by the enzyme glycerol-3-phosphate dehydrogenase (NAD-dependent enzyme, named for the reverse reaction). The glycerol-3-phosphate formed during this reaction is further oxidized by the enzyme of the inner mitochondrial membrane - glycerol-3-phosphate dehydrogenase (FAD-dependent enzyme). Then protons and electrons from FADH 2 move to ubiquinone and further along the CPE.

The glycerol phosphate shuttle system operates in white muscle cells and hepatocytes. However, mitochondrial glycerol-3-phosphate dehydrogenase is absent in cardiac muscle cells. The second shuttle system, which involves malate, cytosolic and mitochondrial malate dehydrogenases, is more universal. In the cytoplasm, NADH reduces oxaloacetate to malate, which, with the participation of a transporter, passes into the mitochondria, where it is oxidized to oxaloacetate by NAD-dependent malate dehydrogenase (reaction 2). NAD reduced during this reaction donates hydrogen to the mitochondrial CPE. However, oxaloacetate, formed from malate, cannot exit the mitochondria into the cytosol on its own, since the mitochondrial membrane is impermeable to it. Therefore, oxaloacetate is converted to aspartate, which is transported to the cytosol, where it is again converted to oxaloacetate. The transformations of oxaloacetate into aspartate and vice versa are associated with the addition and elimination of an amino group. This shuttle system is called malate-aspartate. The result of its work is the regeneration of cytoplasmic NAD+ from NADH.

Both shuttle systems differ significantly in the amount of ATP synthesized. In the first system, the P/O ratio is 2, since hydrogen is introduced into the CPE at the KoQ level. The second system is energetically more efficient, since it transfers hydrogen to the CPE through mitochondrial NAD+ and the P/O ratio is close to 3.

4. ATP balance during aerobic glycolysis and the breakdown of glucose to CO 2 and H 2 O.

ATP release during aerobic glycolysis

The formation of fructose-1,6-bisphosphate from one molecule of glucose requires 2 molecules of ATP. Reactions associated with ATP synthesis occur after the breakdown of glucose into 2 phosphotriose molecules, i.e. at the second stage of glycolysis. At this stage, 2 substrate phosphorylation reactions occur and 2 ATP molecules are synthesized. In addition, one molecule of glyceraldehyde-3-phosphate is dehydrogenated (reaction 6), and NADH transfers hydrogen to the mitochondrial CPE, where 3 molecules of ATP are synthesized by oxidative phosphorylation. In this case, the amount of ATP (3 or 2) depends on the type of shuttle system. Consequently, the oxidation of one glyceraldehyde-3-phosphate molecule to pyruvate is associated with the synthesis of 5 ATP molecules. Considering that 2 phosphotriose molecules are formed from glucose, the resulting value must be multiplied by 2 and then subtracted 2 ATP molecules spent in the first stage. Thus, the ATP yield during aerobic glycolysis is (5H2) - 2 = 8 ATP.

The release of ATP during the aerobic breakdown of glucose to final products as a result of glycolysis produces pyruvate, which is further oxidized to CO 2 and H 2 O in OPC. Now we can evaluate the energy efficiency of glycolysis and OPC, which together constitute the process of aerobic breakdown of glucose to final products. Thus, the ATP yield from the oxidation of 1 mol of glucose to CO 2 and H 2 O is 38 mol of ATP. During the aerobic breakdown of glucose, 6 dehydrogenation reactions occur. One of them occurs in glycolysis and 5 in the OPC. Substrates for specific NAD-dependent dehydrogenases: glyceraldehyde-3-phosphate, fatty acid, isocitrate, b-ketoglutarate, malate. One dehydrogenation reaction in the citrate cycle by succinate dehydrogenase occurs with the participation of the coenzyme FAD. The total amount of ATP synthesized by oxidative phosphorylation is 17 mol of ATP per 1 mol of glyceraldehyde phosphate. To this must be added 3 moles of ATP synthesized by substrate phosphorylation (two reactions in glycolysis and one in the citrate cycle). Considering that glucose breaks down into 2 phosphotrioses and that the stoichiometric coefficient of further transformations is 2, the resulting value must be multiplied by 2, and from the result subtract 2 mol of ATP used in the first stage of glycolysis.

Anaerobic breakdown of glucose (anaerobic glycolysis).

Anaerobic glycolysis is the process of breaking down glucose to form lactate as the final product. This process occurs without the use of oxygen and is therefore independent of the mitochondrial respiratory chain. ATP is formed due to substrate phosphorylation reactions. The overall process equation is:

C 6 H 12 0 6 + 2 H 3 P0 4 + 2 ADP = 2 C 3 H 6 O 3 + 2 ATP + 2 H 2 O.

Anaerobic glycolysis.

During anaerobic glycolysis, all 10 reactions identical to aerobic glycolysis occur in the cytosol. Only the 11th reaction, where pyruvate is reduced by cytosolic NADH, is specific for anaerobic glycolysis. The reduction of pyruvate to lactate is catalyzed by lactate dehydrogenase (the reaction is reversible, and the enzyme is named after the reverse reaction). This reaction ensures the regeneration of NAD+ from NADH without the participation of the mitochondrial respiratory chain in situations involving insufficient oxygen supply to cells.

2.2 Importance of glucose catabolism

The main physiological purpose of glucose catabolism is to use the energy released in this process for the synthesis of ATP

Aerobic breakdown of glucose occurs in many organs and tissues and serves as the main, although not the only, source of energy for life. Some tissues are most dependent on glucose catabolism as a source of energy. For example, brain cells consume up to 100 g of glucose per day, oxidizing it aerobically. Therefore, insufficient supply of glucose to the brain or hypoxia is manifested by symptoms indicating impaired brain function (dizziness, convulsions, loss of consciousness).

Anaerobic breakdown of glucose occurs in muscles, in the first minutes of muscular work, in red blood cells (which lack mitochondria), as well as in various organs under conditions of limited oxygen supply, including tumor cells. The metabolism of tumor cells is characterized by acceleration of both aerobic and anaerobic glycolysis. But predominant anaerobic glycolysis and an increase in lactate synthesis serve as an indicator of an increased rate of cell division when they are insufficiently supplied with a blood vessel system.

In addition to the energy function, the process of glucose catabolism can also perform anabolic functions. Glycolysis metabolites are used to synthesize new compounds. Thus, fructose-6-phosphate and glyceraldehyde-3-phosphate are involved in the formation of ribose-5-phosphate, a structural component of nucleotides; 3-phosphoglycerate can be included in the synthesis of amino acids such as serine, glycine, cysteine (see section 9). In the liver and adipose tissue, acetyl-CoA, formed from pyruvate, is used as a substrate in the biosynthesis of fatty acids and cholesterol, and dihydroxyacetone phosphate is used as a substrate for the synthesis of glycerol-3-phosphate.

Reduction of pyruvate to lactate.

2.3 Regulation of glucose catabolism

Since the main significance of glycolysis is the synthesis of ATP, its rate must correlate with energy expenditure in the body.

Most glycolytic reactions are reversible, with the exception of three, catalyzed by hexokinase (or glucokinase), phosphofructokinase and pyruvate kinase. Regulatory factors that change the rate of glycolysis, and hence the formation of ATP, are aimed at irreversible reactions. An indicator of ATP consumption is the accumulation of ADP and AMP. The latter is formed in a reaction catalyzed by adenylate kinase: 2 ADP - AMP + ATP

Even a small consumption of ATP leads to a noticeable increase in AMP. The ratio of the level of ATP to ADP and AMP characterizes the energy status of the cell, and its components serve as allosteric regulators of the rate of both the general pathway of catabolism and glycolysis.

A change in the activity of phosphofructokinase is essential for the regulation of glycolysis, because this enzyme, as mentioned earlier, catalyzes the slowest reaction of the process.

Phosphofructokinase is activated by AMP but inhibited by ATP. AMP, by binding to the allosteric center of phosphofructokinase, increases the enzyme's affinity for fructose-6-phosphate and increases the rate of its phosphorylation. The effect of ATP on this enzyme is an example of homotropic aschusterism, since ATP can interact with both the allosteric and the active site, in the latter case as a substrate.

At physiological ATP values, the active center of phosphofructokinase is always saturated with substrates (including ATP). An increase in the level of ATP relative to ADP reduces the reaction rate, since ATP under these conditions acts as an inhibitor: it binds to the allosteric center of the enzyme, causes conformational changes and reduces the affinity for its substrates.

Changes in phosphofructokinase activity contribute to the regulation of the rate of glucose phosphorylation by hexokinase. A decrease in phosphofructokinase activity at high ATP levels leads to the accumulation of both fructose-6-phosphate and glucose-6-phosphate, and the latter inhibits hexokinase. It should be recalled that hexokinase in many tissues (with the exception of the liver and pancreatic β-cells) is inhibited by glucose-6-phosphate.

When ATP levels are high, the rate of the citric acid cycle and the respiratory chain decreases. Under these conditions, the process of glycolysis also slows down. It should be recalled that allosteric regulation of OPC and respiratory chain enzymes is also associated with changes in the concentrations of key products such as NADH, ATP and some metabolites. Thus, NADH, accumulating if it does not have time to oxidize in the respiratory chain, inhibits some allosteric enzymes of the citrate cycle

Regulation of glucose catabolism in skeletal muscles.

2.4 Glucose synthesis in the liver (gluconeogenesis)

Some tissues, such as the brain, require a constant supply of glucose. When the intake of carbohydrates in food is insufficient, the blood glucose level is maintained within normal limits for some time due to the breakdown of glycogen in the liver. However, glycogen reserves in the liver are low. They decrease significantly by 6-10 hours of fasting and are almost completely exhausted after a daily fast. In this case, de novo glucose synthesis begins in the liver - gluconeogenesis.

Gluconeogenesis is the process of synthesis of glucose from non-carbohydrate substances. Its main function is to maintain blood glucose levels during periods of prolonged fasting and intense physical activity. The process occurs mainly in the liver and less intensely in the renal cortex, as well as in the intestinal mucosa. These tissues can provide the synthesis of 80-100 g of glucose per day. During fasting, the brain accounts for most of the body's need for glucose. This is explained by the fact that brain cells are not capable, unlike other tissues, of meeting energy needs through the oxidation of fatty acids. In addition to the brain, tissues and cells in which the aerobic breakdown pathway is impossible or limited, for example, red blood cells (they lack mitochondria), cells of the retina, adrenal medulla, etc., need glucose.

The primary substrates of gluconeogenesis are lactate, amino acids and glycerol. The inclusion of these substrates in gluconeogenesis depends on the physiological state of the organism.

Lactate is a product of anaerobic glycolysis. It is formed under any conditions of the body in red blood cells and working muscles. Thus, lactate is constantly used in gluconeogenesis.

Glycerol is released during the hydrolysis of fats in adipose tissue during fasting or prolonged physical activity.

Amino acids are formed as a result of the breakdown of muscle proteins and are included in gluconeogenesis during prolonged fasting or prolonged muscle work.

2.5 Glucose synthesis from lactate

Lactate formed in anaerobic glycolysis is not the end product of metabolism. The use of lactate is associated with its conversion in the liver to pyruvate. Lactate as a source of pyruvate is important not so much during fasting as during normal functioning of the body. Its conversion to pyruvate and the further use of the latter is a way to utilize lactate. Lactate, formed in intensively working muscles or in cells with a predominant anaerobic method of glucose catabolism, enters the blood and then into the liver. In the liver, the NADH/NAD+ ratio is lower than in contracting muscle, so the lactate dehydrogenase reaction proceeds in the opposite direction, i.e. towards the formation of pyruvate from lactate. Next, pyruvate is included in gluconeogenesis, and the resulting glucose enters the blood and is absorbed by skeletal muscles. This sequence of events is called the "glucose-lactate cycle", or "Cori cycle". The Measles cycle performs 2 important functions: 1 - ensures the utilization of lactate; 2 - prevents the accumulation of lactate and, as a consequence, a dangerous decrease in pH (lactic acidosis). Part of the pyruvate formed from lactate is oxidized by the liver to CO 2 and H 2 O. The energy of oxidation can be used for the synthesis of ATP, necessary for gluconeogenesis reactions.

Cori cycle (glucosolactate cycle). 1 - entry of lajugate from the contracting muscle with the blood flow to the liver; 2 - synthesis of glucose from lactate in the liver; 3 - the flow of glucose from the liver through the bloodstream into the working muscle; 4 - the use of glucose as an energy substrate by the contracting muscle and the formation of lactate.

Lactic acidosis. The term "acidosis" means an increase in the acidity of the body's environment (decrease in pH) to values beyond normal limits. In acidosis, either proton production increases or proton excretion decreases (in some cases, both). Metabolic acidosis occurs when the concentration of intermediate metabolic products (acidic in nature) increases due to an increase in their synthesis or a decrease in the rate of breakdown or excretion. If the acid-base state of the body is disturbed, buffer compensation systems quickly turn on (after 10-15 minutes). Pulmonary compensation ensures stabilization of the ratio of HCO 3 -/H 2 CO 3, which normally corresponds to 1:20, and decreases with acidosis. Pulmonary compensation is achieved by increasing the volume of ventilation and, therefore, accelerating the removal of CO 2 from the body. However, the main role in compensating for acidosis is played by renal mechanisms involving the ammonia buffer. One of the causes of metabolic acidosis may be the accumulation of lactic acid. Normally, lactate in the liver is converted back into glucose through gluconeogenesis or oxidized. In addition to the liver, other consumers of lactate are the kidneys and heart muscle, where lactate can be oxidized to CO 2 and H 2 O and used as a source of energy, especially during physical work. The level of lactate in the blood is the result of a balance between the processes of its formation and utilization. Short-term compensated lactic acidosis occurs quite often even in healthy people during intense muscular work. In untrained people, lactic acidosis during physical work occurs as a result of a relative lack of oxygen in the muscles and develops quite quickly. Compensation is carried out by hyperventilation.

With uncompensated lactic acidosis, the lactate content in the blood increases to 5 mmol/l (normally up to 2 mmol/l). In this case, the blood pH can be 7.25 or less (normally 7.36-7.44). An increase in blood lactate may be a consequence of impaired pyruvate metabolism

Disorders of pyruvate metabolism in lactic acidosis. 1 - violation of the use of pyruvate in gluconeogenesis; 2 - violation of pyruvate oxidation. glucose biological catabolism gluconeogenesis

Thus, during hypoxia, which occurs as a result of a disruption in the supply of oxygen or blood to tissues, the activity of the pyruvate dehydrogenase complex decreases and the oxidative decarboxylation of pyruvate decreases. Under these conditions, the equilibrium of the pyruvate-lactate reaction is shifted towards the formation of lactate. In addition, during hypoxia, ATP synthesis decreases, which consequently leads to a decrease in the rate of gluconeogenesis, another pathway for lactate utilization. An increase in lactate concentration and a decrease in intracellular pH negatively affect the activity of all enzymes, including pyruvate carboxylase, which catalyzes the initial reaction of gluconeogenesis.

The occurrence of lactic acidosis is also facilitated by disturbances in gluconeogenesis in liver failure of various origins. In addition, lactic acidosis may be accompanied by hypovitaminosis B1, since a derivative of this vitamin (thiamine diphosphate) performs a coenzyme function as part of the MDC during the oxidative decarboxylation of pyruvate. Thiamine deficiency can occur, for example, in alcoholics with poor diet.

So, the reasons for the accumulation of lactic acid and the development of lactic acidosis may be:

activation of anaerobic glycolysis due to tissue hypoxia of various origins;

liver damage (toxic dystrophies, cirrhosis, etc.);

impaired use of lactate due to hereditary defects in gluconeogenesis enzymes, glucose-6-phosphatase deficiency;

disruption of the MPC due to enzyme defects or hypovitaminosis;

the use of a number of medications, for example biguanides (gluconeogenesis blockers used in the treatment of diabetes).

2.6 Glucose synthesis from amino acids

Under starvation conditions, some muscle tissue proteins break down into amino acids, which are then included in the catabolic process. Amino acids, which during catabolism are converted into pyruvate or metabolites of the citrate cycle, can be considered as potential precursors of glucose and glycogen and are called glycogenic. For example, oxaloacetate, formed from aspartic acid, is an intermediate product of both the citrate cycle and gluconeogenesis.

Of all the amino acids entering the liver, approximately 30% are alanine. This is explained by the fact that the breakdown of muscle proteins produces amino acids, many of which are converted directly into pyruvate or first into oxaloacetate and then into pyruvate. The latter turns into alanine, acquiring an amino group from other amino acids. Alanine from the muscles is transported by the blood to the liver, where it is again converted into pyruvate, which is partially oxidized and partially included in glucoseogenesis. Therefore, there is the following sequence of events (glucose-alanine cycle): muscle glucose > muscle pyruvate > muscle alanine > liver alanine > liver glucose > muscle glucose. The entire cycle does not increase the amount of glucose in the muscles, but it solves the problem of transporting amine nitrogen from the muscles to the liver and prevents lactic acidosis.

Glucose-alanine cycle

2.7 Glucose synthesis from glycerol

Glycerol can only be used by tissues that contain the enzyme glycerol kinase, such as the liver and kidneys. This ATP-dependent enzyme catalyzes the conversion of glycerol to b-glycerophosphate (glycerol-3-phosphate). When glycerol-3-phosphate is included in gluconeogenesis, it is dehydrogenated by NAD-dependent dehydrogenase to form dihydroxyacetone phosphate, which is further converted into glucose.

Conversion of glycerol to dihydroxyacetone phosphate

Thus, we can say that the biological role of glucose in the body is very important. Glucose is one of the main sources of energy in our body. It is an easily digestible source of valuable nutrition that increases the body's energy reserves and improves its functions. The main importance in the body is that it is the most universal source of energy for metabolic processes.

In the human body, the use of a hypertonic glucose solution promotes vasodilation, increased contractility of the heart muscle and an increase in urine volume. As a general tonic, glucose is used for chronic diseases that are accompanied by physical exhaustion. The detoxification properties of glucose are due to its ability to activate the liver’s functions to neutralize poisons, as well as a decrease in the concentration of toxins in the blood as a result of an increase in the volume of circulating fluid and increased urination. In addition, in animals it is deposited in the form of glycogen, in plants - in the form of starch, the polymer of glucose - cellulose is the main component of the cell walls of all higher plants. In animals, glucose helps survive frosts.

In short, glucose is one of the vital substances in the life of living organisms.

List of used literature

1. Biochemistry: textbook for universities / ed. E.S. Severina - 5th ed., - 2014. - 301-350 art.

2. T.T. Berezov, B.F. Korovkin "Biological chemistry".

3. Clinical endocrinology. Guide / N. T. Starkova. - 3rd edition, revised and expanded. - St. Petersburg: Peter, 2002. - pp. 209-213. - 576 p.

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What is glucose?

Glucose or dextrose is a colorless or white, odorless, finely crystalline powder with a sweet taste. Glucose can be called a universal fuel, since most of the body's energy needs are covered by it.

This substance must be constantly present in our blood. Moreover, both its excess and its deficiency are dangerous for the body. So, during hunger, the body begins to “use for food” what it is built from. Then muscle proteins begin to be converted into glucose, which can be quite dangerous.

Color scale of indicator visual test strips

These test strips are used to detect blood sugar abnormalities at home.

Official blood glucose standards approved by WHO.

Food-glucose-glycogen system

Glucose enters the human body with carbohydrates. Once in the intestines, complex carbohydrates are broken down into glucose, which is then absorbed into the blood. Some of the glucose is used for energy needs, another part can be stored as fat reserves, and some is stored as glycogen. After the food is digested and the flow of glucose from the intestines stops, the reverse conversion of fats and glycogen into glucose begins. This is how our body maintains constant blood glucose concentration.

Conversion of proteins and fats into glucose and back is a process that takes a lot of time. But the interconversion of glucose and glycogen occurs very quickly. Therefore, glycogen plays the role of the main storage carbohydrate. In the body, it is deposited in the form of granules in various types of cells, but mainly in the liver and muscles. The glycogen reserve in a person of average physical development can provide him with energy throughout the day.

Hormone regulators

The conversion of glucose to glycogen and vice versa is regulated by a number of hormones. Insulin lowers the concentration of glucose in the blood. And it increases - glucagon, somatotropin, cortisol, thyroid hormones and adrenaline. Disturbances in these reversible reactions between glucose and glycogen can lead to serious diseases, the best known of which is diabetes mellitus.

Measuring blood glucose

The main test for diabetes is measuring blood glucose.

Concentration glucose is different in capillary and venous blood and fluctuates depending on whether the person has eaten or is hungry. Normally, when measured on an empty stomach (at least 8 hours after the last meal), the glucose content in capillary blood is 3.3 - 5.5 (mmol/l), and in venous blood 4.0 - 6.1 (mmol/l). ). Two hours after eating, the glucose level should not exceed 7.8 (mmol/l), for both capillary and venous blood. If during the week, when measuring on an empty stomach, the glucose level does not fall below 6.3 mmol/l, then you should definitely contact an endocrinologist and conduct an additional examination of the body.

Hyperglycemia - a lot of glucose in the blood

Hyperglycemia develops most often in diabetes mellitus. Glucose levels may increase if:

diabetes mellitus
stress, strong emotional tension
diseases of the endocrine system, pancreas, kidneys
myocardial infarction

Endocrinologist

During stressful situations, blood glucose may increase. The fact is that the body, in response to an acute situation, releases stress hormones, which, in turn, increase blood glucose.

Hyperglycemia occurs:

light - 6.7 mmol/l
moderate - 8.3 mmol/l
severe - more than 11.1 mmol/liter
coma state - 16.5 mmol/l
coma - more than 55.5 mmol/l

Hypoglycemia - low blood glucose

Hypoglycemia A condition is considered when the blood glucose concentration is below 3.3 mmol/l. Clinical manifestations of hypoglycemia begin after the sugar level drops below 2.4 - 3.0 mmol/l. With hypoglycemia the following are observed:

muscle weakness
impaired motor coordination
confusion
increased sweating

Glucose levels decrease when:

diseases of the pancreas and liver
some diseases of the endocrine system
eating disorders, starvation
overdose of hypoglycemic drugs and insulin

With very severe hypoglycemia, it can develop.

Glucose in medicine

Glucose solution is used in the treatment of a number of diseases, for hypoglycemia and various intoxications, as well as for diluting certain medications when administered into a vein.

Glucose- an essential substance that plays a very important role in the functioning of our body.

An Israeli doctor refuted the stereotype that sugar provokes the development of diabetes and named other causes of the disease

is a natural dextrose found in berries and fruits. The main content of this substance can be found in grape juice, which is why the substance received its second name - sweet grape sugar.

Glucose is found in large quantities in fruits and berries.

Glucose is a monosaccharide with a hexose. The composition includes starch, glycogen, cellulose, lactose, sucrose and maltose. Once in, grape sugar is broken down into fructose.

The crystallized substance is colorless, but with a pronounced sweet taste. Glucose can dissolve in water, especially in zinc chloride and sulfuric acid.

This makes it possible to create medical preparations based on grape sugar to compensate for its deficiency. Compared to fructose and sucrose, this monosaccharide is less sweet.

Significance in the life of animals and humans

Why is glucose so important in the body and what is it for? In nature, this chemical is involved in the process of photosynthesis.

This is because glucose is able to bind and transport energy to cells. In the body of living beings, glucose, due to the energy produced, plays an important role in metabolic processes. Main benefits of glucose:

Grape sugar is an energy fuel that allows cells to function smoothly.
70% of glucose enters the human body through complex carbohydrates, which, when they enter the body, are broken down into fructose, galactose and dextrose. Otherwise, the body produces this chemical, using its own stored reserves.
Glucose penetrates into the cell, saturates it with energy, due to which intracellular reactions develop. Metabolic oxidation and biochemical reactions occur.

Many cells in the body are capable of producing grape sugar on their own, but not the brain. An important organ cannot synthesize glucose, so it receives nutrition directly through the blood.

The level of glucose in the blood, for normal functioning of the brain, should not be lower than 3.0 mmol/l.

Excess and Deficiency

Overeating can cause excess glucose.

Glucose is not absorbed without insulin, a hormone that is produced in.

If there is a deficiency of insulin in the body, then glucose is not able to penetrate the cells. It remains unprocessed in the human blood and is enclosed in an eternal cycle.

As a rule, with a lack of grape sugar, cells weaken, starve and die. This relationship is studied in detail in medicine. Now this condition is classified as a serious disease and is called.

In the absence of insulin and glucose, not all cells die, but only those that are not able to independently absorb the monosaccharide. There are also insulin-independent cells. Glucose is absorbed in them without insulin.

These include brain tissue, muscles, and red blood cells. These cells are nourished by incoming carbohydrates. You may notice that during fasting or poor nutrition, a person’s mental abilities change significantly, weakness and anemia (anemia) appear.

According to statistics, glucose deficiency occurs in only 20%, the remaining percentage is due to an excess of the hormone and monosaccharide. This phenomenon is directly related to overeating. The body is not able to break down carbohydrates that come in large quantities, which is why it simply begins to store glucose and other monosaccharides.

If glucose is stored in the body for a long time, it is converted into glycogen, which is stored in the muscles. In this situation, the body falls into a stressful state when there is too much glucose.

Since the body cannot independently remove large amounts of grape sugar, it simply stores it in adipose tissue, due to which a person rapidly gains excess weight. This whole process requires a large amount of energy (breakdown, transformation of glucose, deposition), so there is a constant feeling of hunger and a person consumes carbohydrates 3 times more.

For this reason, it is important to consume glucose correctly. Not only in diets, but also in proper nutrition, it is recommended to include complex carbohydrates in the diet, which are slowly broken down and evenly saturate the cells. By using simple carbohydrates, grape sugar begins to be released in large quantities, which immediately fills the adipose tissue. Simple and complex carbohydrates:

Simple: confectionery, honey, sugar, preserves and jams, carbonated drinks, white bread, sweet vegetables and fruits, syrups.
Complex: found in beans (peas, beans, lentils), cereals, beets, potatoes, carrots, nuts, seeds, pasta, cereals and grains, black and rye bread, pumpkin.

Use of glucose

For several decades now, humanity has learned to obtain glucose in large quantities. For this purpose, cellulose and starch hydrolysis are used. In medicine, glucose-based drugs are classified as metabolic and detoxifying.

They are able to restore and improve metabolism, and also have a beneficial effect on redox processes. The main form of release is a freeze-dried combination and a liquid solution.

Who benefits from glucose?

Regular consumption of glucose affects the baby's weight in the womb.

The monosaccharide does not always enter the body with food, especially if the diet is poor and not combined. Indications for use of glucose:

During pregnancy and suspected low fetal weight. Regular consumption of glucose affects the baby's weight in the womb.
When the body is intoxicated. For example, chemicals such as arsenic, acids, phosgene, carbon monoxide. Glucose is also prescribed for drug overdose and poisoning.
For collapse and hypertensive crisis.
After poisoning as a restorative agent. Especially with dehydration due to vomiting or in the postoperative period.
For hypoglycemia, or low blood sugar. Suitable for diabetes, check regularly using glucometers and analyzers.
Liver diseases, intestinal pathologies due to infections, and hemorrhagic diathesis.
Used as a restorative remedy after long-term infectious diseases.

Release form

There are three forms of glucose release:

Intravenous solution. Prescribed to increase osmotic blood pressure, as a diuretic, to dilate blood vessels, to relieve tissue swelling and remove excess fluid, to restore the metabolic process in the liver, and also as nutrition for the myocardium and heart valves. It is produced in the form of dried grape sugar, which is dissolved in concentrates with different percentages.
. Prescribed to improve general condition, physical and intellectual activity. Acts as a sedative and vasodilator. One tablet contains at least 0.5 grams of dry glucose.
Solutions for infusions (droppers, systems). Prescribed to restore water-electrolyte and acid-base balance. Also used in dry form with a concentrated solution.

How to check your blood sugar levels, watch the video:

Contraindications and side effects

Glucose is not prescribed to persons suffering from diabetes mellitus and pathologies that increase blood sugar levels. If prescribed incorrectly or self-medicated, acute heart failure, loss of appetite and disruption of the insular apparatus may occur.

Also, glucose should not be administered intramuscularly, as this can cause necrosis of subcutaneous fat. With rapid administration of a liquid solution, hyperglucosuria, hypervolemia, osmotic diuresis and hyperglycemia may occur.

Unusual uses of glucose

Glucose is used in baked goods to make the product soft and fresh.

In the form of syrup, grape sugar is added to the dough when baking bread. Because of this, bread can be stored for a long time at home without becoming stale or drying out.

You can also make this bread, but using glucose in ampoules. Liquid candied grape sugar is added to baked goods, such as muffins or cakes.

Glucose provides confectionery products with softness and long-lasting freshness. Dextrose is also an excellent preservative.

Eye baths, or rinses, with a dextrose-based solution. This method helps to get rid of vascularized corneal opacification, especially after keratitis. The baths are used according to strict instructions to prevent delamination of the corneal layer. Glucose is also dropped into the eye, used as homemade drops or in diluted form.

Used for finishing textiles. A weak glucose solution is used as a fertilizer for wilting plants. To do this, purchase grape sugar in an ampoule or dry form and add it to water (1 ampoule: 1 liter). Flowers are regularly watered with this water as they dry. Thanks to this, the plants will become green, strong and healthy again.

Dry glucose syrup is added to baby food. Also used during diets. It is important to monitor your health at any age, so it is recommended to pay attention to the amount of monosaccharides that you eat along with easily digestible carbohydrates.

With a deficiency or excess of glucose, disruptions occur in the cardiovascular, endocrine, and nervous systems, while brain activity is significantly reduced, metabolic processes are disrupted, and immunity deteriorates. Help your body by using only healthy foods such as fruits, honey, vegetables and grains. Limit yourself from unnecessary calories that come into your body through waffles, cookies, pastries and cakes.

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Molecule structure.

When studying the composition of glucose, it was found that its simplest formula is CH 2 O, and its molar mass is 180 g/mol. From this we can conclude that the molecular formula of glucose is C 6 H 12 O 6.

To establish the structural formula of a glucose molecule, it is necessary to know its chemical properties. It has been experimentally proven that one mole of glucose reacts with five moles of acetic acid to form an ester. This means that there are five hydroxyl groups in a glucose molecule. Since glucose with an ammonia solution of silver oxide gives a “silver mirror” reaction, its molecule must also contain an aldehyde group.

It has also been experimentally proven that glucose has an unbranched carbon chain.

Based on these data, the structure of the glucose molecule can be expressed as follows:

Biological significance of glucose, its use.

Glucose is a necessary component of food, one of the main participants in metabolism in the body, it is very nutritious and easily digestible. During its oxidation, more than a third of the energy resource used in the body is released - fats, but the role of fats and glucose in the energy of different organs is different. The heart uses fatty acids as fuel. Skeletal muscles need glucose to “start”, but nerve cells, including brain cells, work only on glucose. Their need is 20-30% of the generated energy. Nerve cells need energy every second, and the body receives glucose when eating. Glucose is easily absorbed by the body, so it is used in medicine as a strengthening remedy. Specific oligosaccharides determine blood type. In confectionery for making marmalade, caramel, gingerbread, etc. The fermentation processes of glucose are of great importance. So, for example, when sauerkraut, cucumbers, and milk are pickled, lactic acid fermentation of glucose occurs, as well as when ensiling feed. In practice, alcoholic fermentation of glucose is also used, for example, in the production of beer. Cellulose is the starting material for the production of silk, cotton wool, and paper.
Carbohydrates are indeed the most common organic substances on Earth, without which the existence of living organisms is impossible.
In a living organism, during metabolism, glucose is oxidized, releasing a large amount of energy:

Application.

Glucose refers to carbohydrates and is one of the products metabolism human and animal bodies. In metabolism, glucose has mainly energy value. With the complete breakdown of 1 g of glucose, 17.15 kJ (4.1 kcal) of heat is released. The energy released in this process ensures the activity of the body's cells. The energy value of glucose is especially high for such intensively functioning organs as the central nervous system, heart, and muscles. In this regard, glucose is widely used as tonic for many chronic diseases accompanied by physical exhaustion.

Glucose increases the liver’s ability to neutralize various poisons, which largely explains the antitoxic properties of glucose. In addition, in case of poisoning, the use of large quantities of glucose solutions is accompanied by a decrease in the concentration of poisons in the blood due to an increase in the mass of fluid circulating in the vessels and increased urination.

1.Polysaccharides (glycans) are molecules of polymeric carbohydrates connected by a long chain, united together by a glycosidic bond, and upon hydrolysis they become an integral part of monosaccharides or oligosaccharides

2. Physical properties of starch. It is a white powder, insoluble in cold water. In hot water it swells to form a paste.

.Being in nature

Starch, the main source of reserve energy in plant cells, is formed in plants during photosynthesis and accumulates in tubers, roots, seeds: 6CO 2 + 6H 2 O light, chlorophyll→ C 6 H 12 O 6 + 6O 2

nC 6 H 12 O 6 → (C 6 H 10 O 5) n + nH 2 O

glucose starch

Contained in potato tubers, grains of wheat, rice, corn. Glycogen (animal starch) is formed in the liver and muscles of animals.

.Biological role.

Starch is one of the products of photosynthesis, the main nutrient reserve of plants. Starch is the main carbohydrate in human food.

3. 1) Under the action of enzymes or when heated with acids (hydrogen ions serve as a catalyst), starch, like all complex carbohydrates, undergoes hydrolysis. In this case, soluble starch is formed first, then less complex substances - dextrins. The final product of hydrolysis is glucose. The overall reaction equation can be expressed as follows:

There is a gradual breakdown of macromolecules. Hydrolysis of starch is its important chemical property.
-glucose. The process of starch formation can be expressed as follows (polycondensation reaction): a2) Starch does not give the “silver mirror” reaction, but the products of its hydrolysis do. Starch macromolecules consist of many cyclic molecules

3) A characteristic reaction is the interaction of starch with iodine solutions. If an iodine solution is added to a cooled starch paste, a blue color appears. When the paste is heated, it disappears, and when cooled, it appears again. This property is used in determining starch in food products. For example, if a drop of iodine is applied to a cut potato or a slice of white bread, a blue color appears.

4.cellulose structure

Cellulose is a substance widely distributed in plant

world. It is found in both annual and perennial plants, in particular in tree species.

The modern theory of the structure of cellulose answers the following basic questions:

The structure of cellulose macromolecules: the chemical structure of the elementary unit and the macromolecule as a whole; conformation of the macromolecule and its units.

Molecular weight of cellulose and its polydispersity.

Cellulose structure: equilibrium phase state of cellulose (amorphous or crystalline); types of bonds between macromolecules; supramolecular structure; structural heterogeneity of cellulose; structural modifications of cellulose.

2) The structure of the cellulose macromolecule can be represented by the formula

5.hydrolysis of cellulose

С6Н10О5)n +nH2O=nC6H12O6 beta-glucose

Acetate fibers- one of the main types of artificial fibers; obtained from cellulose acetate. Depending on the type of feedstock, triacetate fiber (from triacetyl cellulose) and acetate fibers themselves are distinguished

Viscose- (from Late Lat. viscosus- chilly) highly viscous concentrated solution of cellulose xanthate in a dilute NaOH solution.

7. CELLULOSE is the main part of plant walls. (Figure “Natural materials containing cellulose” - slide 7, lesson 21). Relatively pure cellulose are fibers from cotton, jute and hemp. Wood contains from 40 to 50% cellulose, straw - 30%. Plant cellulose serves as a nutrient for herbivores, whose bodies contain enzymes that break down fiber.
From cellulose (numerous artificial fibers, polymer films, plastics, smokeless powder, varnishes are made. A large amount of cellulose is used for the production of paper. By saccharification of cellulose, glucose is obtained; it is used for the production of ethyl alcohol. Ethanol, p