Glucose + 2 ADP + 2 Over + + 2 H 3 PO 4  2 Pyruvate + 2Af + 2 Nadn + 2 H +

Shuttle mechanisms.

The transfer of hydrogen from the cytosolic NADP in mitochondria occurs with the participation of special mechanisms called shuttle. The essence of these mechanisms is reduced to the fact that NADP in cytosol restores some compound capable of penetrating mitochondria; In mitochondria, this compound is oxidized, restoring intramito-one-eyed over +, and again goes into cytosol. The most active malate aspartate system acting in the mitochondria of the liver, kidney and heart. On each pair of electrons of the cytosolic nastrod, transmitted to oxygen on this system, 3 ATP molecules are formed.

In skeletal muscles and the brain, the transfer of recovery equivalents from the cytosol nasturn is carried out by a glycerol phosphate system. In this case, the rehabilitation equivalents are transmitted to the electron transfer circuit through complex II, and therefore only 2 ATP molecules are synthesized.

ATP output with aerobic glycolysis.

The main physiological significance of the aerobic decay of glucose is to use its energy for the synthesis of ATP.

The biggest dependence on aerobic glycolysis is the brain. It consumes 100 g of glucose per day. In a state of basic exchange, about 20% oxygen is consumed by the brain. Therefore, the lack of glucose or oxygen is manifested, first of all, symptoms from the central nervous system - dizziness, loss of consciousness, convulsions.

Anaerobic glycoliz.

In the aerobic conditions, the product of glycolysis in tissues is pyruvate, and NADP, formed during oxidation, is reoccloyed due to molecular oxygen. In anaerobic conditions, i.e., with a lack of oxygen in tissues, for example, in stressful skeletal muscles, the resulting NADP is repeated not due to oxygen, but due to the pyruvate, which is restored to the lactate (milk acid). Restoration of pyruvate to lactate catalyzes isoenzyme lactate dehydrogenase.

Lacatdehydrogenase is a tetramer containing protuers of two types - M (Muscle) and H (Heart). It is known 5 isoenzymes that differ in a set of protéer.

Isomeric forms of LDH 1 and LDH 2 are found in the brain, heart, cortical substance kidney, i.e. In tissues with intense oxygen supply. Form LDH 3 - in the pancreas, LDH 4 and LDH 5 in skeletal muscles, liver, cereal brain substance, i.e. In tissues with a less intense supply of oxygen. All these forms of enzymes differ significantly to the maximum response rate and Mihaelis constants for lactate and pyruvate. LDH 5 quickly catalyzes the recovery of pyruvate into lactate at low concentrations of lactate. LDH 1 catalyzes the rapid oxidation of lactate into pyruvate in the heart muscle.

In glucose cells, it can turn into fatty acids, amino acids, glycogen and oxidize in various catabolic paths.

Glucose oxidation is called glikoliz. Glucose can be oxidized to lactate to pyruvate. In aerobic conditions, the main product is pyruvate, such a way is called aerobic glycolizom. With a lack of oxygen, the product prevails - lactate. This way of oxidation is called anaerobic Glycolizom.

The process of the aerobic decay of glucose can be divided into three parts: the transformation-specific glucose conversion, ending with the formation of pyruvate (aerobic glycolysis); Common path of catabolism (oxidative decarboxylation and CLK); breathing chain.

As a result of these glucose processes decomposes to CO 2 and H 2 O, and the released energy is used to synthesize ATP.

Enzymatic reactions.

The decay of glucose to pyruvate can also be divided into two stages. The first stage (glucose  glyceral dehydphosphate) requires energy in the form of ATP (2 ATP).

E 1 - hexokinas or glucocinate

E 2 - glucosophosphatisomeraza

E 3 - phosphofructocinase

E 4 - fruchozodiphosphaldolaza

E 5 - triosphosphiatzomeraza

The second stage (glyceraldehyde  pyruvate) flows with the yield of energy in the form of ATP and NADP (4 ATP and 2 NADH).

E 6 - glyceraldehyde-3-Food Dehydrogenase

E 7 - phosphoglyceratinaza

E 8 - phosphoglyceratphosfomutaza

E 9 - eNOLHIDRATAZA

E 10. - Priusvatkinaza

Features of enzymes of glycolysis.

In the path of glycolysis, three reactions are irreversible (reaction 1 - glucocinate Reaction 3 - phofofructureinaznaya Reaction 10 - piruvatakenaznaya). They are catalyzed by regulatory enzymes and determine the speed of the entire glycolysis process. In addition, it is these reactions that differ from the reactions of the return path - glucose synthesis ( gloundogenesis).

Hexokinase and glucocinate

The glucocinase reaction is the first ATP-dependent glycolysis reaction. It is catalyzed by tissue-specific enzymes - hexokinase.A person knows 4 hexokinez isomers (Types I - IV). Isoerment IV type - glucocinate. Glucocinate is only in the liver and has a high meaning to M to glucose. This leads to the fact that the enzyme is saturated with a substrate only with very high glucose concentrations. Hxokinase catalyzes glucose phosphorylation with any (including low) glucose concentrations and inhibited by product glucose-6-phosphate. Glucocainase is not inhibited by glucose-6 phosphate. With increasing glucose concentration after meals, the rate of glucocinase reaction increases. The glucose-6-phosphate does not pass through the cell membranes and is delayed in the cell, so more glucose is delayed in the liver. Thus, glucocaine is a glucose buffer in the blood. At the same time, in tissues, the energy exchange of which depends on glucose, is localized with a low value to m.

Glucosophosphatisomeraza

The enzyme is almost equal to M for glucose-6-phosphate and fructose-6-phosphate. This enzyme is differently called hexosophosphatisomerasis.

Phosphofructocinase

This enzyme catalyzes only a direct reaction, i.e. This glycolysis reaction is irreversible and determines the speed of the entire process.

Fruchozodiphosphaldolaza catalyzes glycolysis and gluconeogenesis reactions.

Trophosphatisomeraza Catalyzes equilibrium reaction, and equilibrium is shifted towards glycolysis or gluconeogenesis on the principle of mass action.

Glyceraldehyde-3-phosphate dehydrogenase Catalyzes glycolysis and gluconeogenesis reactions.

Phosphoglyceratinaza Catalyzes reversible reaction (glycolysis and gluconeogenesis). This reaction is of great importance in red blood cells, because Forming 1,3-diphosphoglycerat under the action of the enzyme diphosphogliteratmutase The 2,3-diphosphoglycerate (DFG) is converted - an HB affinity regulator to oxygen.

Phosphoglyceratphosfomutaza and eNOLHIDRATAZA Catalize the conversion of relatively low-energy communication in 3-phosphoglycerat in high-energy form, and then in ATP.

Piruvatkinaza - a regulatory enzyme that catalyzes an irreversible reaction in which the high-energy phosphian phosphoenolpiruvat turns into ATP.

Piruvat further oxidizes in mitochondria. The decay of glucose to pyruvate proceeds in the cytoplasm, so there is a special carrier of pyruvate in mitochondria by the simpliation mechanism with H +. The formed NADS should also be transported in mithodaria for oxidation in the electron transfer circuit.

IN anaerobic process Pyerogradic acid is restored to lactic acid (lactate), so in microbiology anaerobic glycoliz is called lactic acid fermentation. Laktat is metabolic stilland then it does not turn into anything, the only opportunity to dispose of lactate is to oxidize it back into the pyruvate.

Many organism cells are capable of anaerobic glucose oxidation. For erythrocyteit is the only source of energy. Cells skeletal muscles Due to the oxless glucose splitting capable of performing powerful, fast, intensive work, such as, for example, running to short distances, voltage in power sports. Outside of physical exertion, the oxless oxidation of glucose in cells is enhanced with hypoxia - with different kinds of anemia, P. circulatory impairment In the tissues, regardless of the cause.

Glikoliz

Anaerobic transformation of glucose is localized in citoxoleand includes two stages of 11 enzymatic reactions.

The first stage of glycolysis

The first stage of glycolysis - preparatoryhere is the cost of ATP energy, glucose activation and formation of it triosophosphate.

First reaction Glycolize is reduced to the conversion of glucose into the reaction-capable compound due to phosphorylation of the 6th, not included in the ring, carbon atom. This reaction is the first in any conversion of glucose, catalyzed by hexokinase.

Second reaction It is necessary to eliminate another carbon atom from the ring for its subsequent phosphorylation (enzyme glucosophosphate Isomeraza). As a result, fructose-6-phosphate is formed.

Third reaction - Enzyme phosphofructocinase Phosphorylates fructo-6-phosphate with the formation of an almost symmetric fructo-1,6-diphosphate molecule. This reaction is the main in the regulation of the glycolysis rate.

IN fourth reaction Fructose-1,6-diphosphate is cut in half fructose-1,6-diphosphatealdolase with the formation of two phosphorylated triose-isomers - aldose glyceraldehyda(GAF) and ketosis dioxiacetone(DAF).

Fifth reaction Preparatory stage - transition of glyceralholdphosphate and dioxiacetone phosphate in each other with participation triosophosphatisomerase. The equilibrium of the reaction is shifted in favor of dioxiacetone phosphate, its share is 97%, the proportion of glyceraldehydphosphate is 3%. This reaction, with all its simplicity, determines the further fate of glucose:

  • with a shortage of energy in the cell and activation of the oxidation of glucose, dioxiacetone phosphate turns into glyceraldehydphosphate, which is further oxidized at the second stage of glycolysis,
  • with a sufficient amount of ATP, on the contrary, the glyceral dehydphosphate is is amazed into dioxiacetone phosphate, and the latter is sent to the synthesis of fats.

The second stage of glycolysis

The second stage of glycolysis is liberation of energycontained in glyceraldehydphosphate and stock in shape ATF.

Sixth reaction Glycolysis (enzyme glyceraldehydphosphate-dehydrogenase) - oxidation of the glyceraldehydphosphate and the addition of phosphoric acid to it leads to the formation of a macroergic compound of 1,3-diphosphoglycerolic acid and NADP.

IN seventh reaction (enzyme phosphoglyceratinaza) The energy of phosphoeter communication, concluded in the 1,3-difosphoglycera, is spent on the formation of ATP. The reaction obtained an additional name - that clarifies the source of energy to obtain a macroeergic bond to ATP (from the substrate of the reaction), in contrast to oxidative phosphorylation (from the electrochemical gradient of hydrogen ions on mitochondria membrane).

Eighth reaction - 3-phosphoglycerat synthesized in the previous reaction under the influence phosphoglyceratmutase is isomerized in 2-phosphoglycerat.

Ninth reaction - Enzyme enaolaza Removes the water molecule from 2-phosphoglycerolic acid and leads to the formation of macroeergic phosphoeter communication in the composition of phosphoenolpiruvat.

Tenth reactionglycolize - another substrate phosphorylation reaction - lies in the transfer of the piruvatakenase of macroehergic phosphate with phosphoenolpiruvat on the ADP and the formation of peyrogradic acid.

To understand what Glycoliz is, you will have to turn to Greek terminology, because this term has occurred from Greek words: Glycos - Sweet and lysis - splitting. From the word glycos is the name of glucose. Thus, under this term, the process of saturation of glucose oxygen is meant, as a result of which one molecule of the sweet substance disintegrates into two peer-co-acid microparticles. Glyicoliz is a biochemical reaction occurring in living cells, and aimed at cleavage of glucose. There are three options for glucose decomposition, and aerobic glycoliz is one of them.

This process consists of a number of intermediate chemical reactions accompanied by the release of energy. This lies the main essence of glycolysis. Released energy is spent on the overall life of the living organism. The general glucose splitting formula looks like this:

Glucose + 2nd + 2adf + 2pi → 2 Pyruvate + 2NV + 2N + + 2Adf + 2N2O

Aerobic glucose oxidation with subsequent splitting of its six-carbon molecule is carried out by 10 intermediate reactions. The first 5 reactions, combines the preparatory phase of preparation, and subsequent reactions are aimed at the formation of ATP. In the course of reactions, stereoscopic isomers of sugar and their derivatives are formed. The main accumulation of energy by cells occurs in the second phase associated with the formation of ATP.

Stages of oxidative glycolysis. Phase 1.

In aerobic glycolisis, 2 phases are distinguished.

The first phase is preparatory. It enters the glucose to react with 2 ATP molecules. This phase consists of 5 consecutive stages of biochemical reactions.

1st stage. Glucose phosphorylation

Phosphorylation, i.e., the process of transferring phosphoric acid residues in the first and subsequent reactions is carried out due to the molecules of adezintrifosphoric acid.

In the first stage, the residues of phosphoric acid from the adezenthosphate molecules are transferred to the molecular structure of glucose. During the process, glucose-6-phosphate is obtained. As a catalyst, hexokinase is in the process, accelerating the process using magnesium ions acting as a cofactor. Magnesium ions are also involved in other glycolysis reactions.

2nd stage. Education of the isomer of glucose-6-phosphate

At the 2nd stage, isomerization of glucose-6-phosphate in fructose-6-phosphate occurs.

Isomerization - the formation of substances having the same weight, the composition of chemical elements, but with different properties due to different location of atoms in the molecule. Isomerization of substances is carried out under the action of external conditions: pressure, temperatures, catalysts.

In this case, the process is carried out under the action of the catalyst of phosphoglucosoisomerase with the participation of MG + ions.

3rd stage. Phosphorylation of fructose-6-phosphate

At this stage, the phosphoryl group is attached due to ATP. The process is carried out with the participation of the enzyme phosphofuctocinase-1. This enzyme is intended only for participation in hydrolysis. As a result of the reaction, fructose-1,6-bisphosphate and adezenthosphate nucleotide are obtained.

ATP - adesenthriphosphate, a unique source of energy in a living organism. It is a rather complicated and bulky molecule consisting of hydrocarbon, hydroxyl groups, nitrogen and phosphoric acid groups with one free bond collected in several cyclic and linear structures. Energy release occurs as a result of the interaction of phosphoric acid residues with water. The hydrolysis of ATP is accompanied by the formation of phosphoric acid and the release of 40-60 J energy, which the body spends on its livelihood.

But before the phosphorylation of glucose due to the adesenthriphosphate molecule should occur, that is, the transfer of phosphoric acid residue in glucose.

4th stage. Disintegration of fruit-1,6-diphosphate

In the fourth reaction, fructose-1,6-diphosphate disintegrates into two new substances.

  • Dioxiacetone phosphate,
  • Glycerald Aldehyde 3-phosphate.

In this chemical process, aldolaza, an enzyme involved in the energy exchange, and necessary in the diagnosis of a number of diseases are acting as a catalyst.

5th stage. The formation of trioseophosphate isomers

And finally, the last process is the isomerization of triosisophosphates.

Glycerald-3-phosphate will continue to participate in the process of aerobic hydrolysis. And the second component - dioxiacetone phosphate with the participation of the enzyme triosophosphatisomerase is converted to glyceraldehyde-3-phosphate. But this transformation is reversible.

Phase 2. Synthesis of adezenthriphosphate

In this phase of glycolysis will be accumulated as ATP biochemical energy. The adezenthosphate is formed from adezeindiphosphate due to phosphorylation. And also formed Nadn.

Abbreviation Nadn has a very complex and difficult decoding - nicotinamedadenindinucleotide for a non-specialist. Nadn is a coenzyme, a non-biotheal compound, which participates in the chemical processes of a living cell. It exists in two forms:

  1. oxidized (NAD +, NADOX);
  2. restored (NADH, NADRED).

In the exchange of substances NAD takes part in oxidative reaction reactions transporting electrons from one chemical process to another. Righting, or taking an electron, the molecule is converted from NAD + in NADH, and vice versa. In the living organism over is produced from tryptophan or aspartate amino acids.

Two microparticles of glyceraldehyde-3-phosphate are reactions, during which pyruvate is formed, and 4 ATP molecules. But the final output of the adezenthosphate will be 2 molecules, since two are spent in the preparatory phase. The process continues.

6th Stage - Oxidation of glyceraldehyde-3-phosphate

In this reaction, oxidation and phosphorylation of glyceraldehyde-3-phosphate occurs. As a result, 1,3-difosphoglycerin acid is obtained. Glyceraldehyde-3-phosphatehydehyde-3-phosphate dehydrogenase participates in acceleration of the reaction

The reaction occurs with the participation of the energy obtained from the outside, therefore it is called Endergonic. Such reactions proceed in parallel with exercimic, that is, emitting, which gives energy. In this case, this reaction is the following process.

7th stage. Moving phosphate group with 1,3-diphosphoglycerat to adezeindiphosphate

In this intermediate reaction, the phosphoryl group is transferred to phosphoglycerat seater with 1,3-dithosphoglycerat to adezeindiphosphate. As a result, 3-phosphoglycerat and ATP are obtained.

The enzyme of phosphoglyceraticinase acquired its name for the ability to catalyze the reaction in both directions. This enzyme also transports the phosphate residue from adezenthosphate to 3-phosphoglycerat.

The 6th and 7th reactions are often considered as a single process. The 1,3-diphosphoglycerat is considered as an intermediate product. Together the 6th and 7th reactions look like this:

Glyceraldehyde-3-phosphate + adp + pi + nad + ⇌3 -phosphoglycerat + ATP + NADH + N +, ΔG'o \u003d -12.2 kJ / mol.

And the total of these 2 processes exempt part of the energy.

8th stage. Transferring phosphoryl group with 3-phosphoglycerat.

Obtaining 2-phosphoglycerat - the process is reversible, occurs under a catalytic effect of phosphoglyceratmutase enzyme. The phosphoryl group is transferred from a bivalent carbon atom of 3-phosphoglycerat to a trivalent 2-phosphoglycerat atom, 2-phosphoglycerin acid is formed. The reaction passes with the participation of positively charged magnesium ions.

9th stage. Water release from 2-phosphoglycerat

This reaction in its essence is the second glucose splitting reaction (the first stage was the first stage). In it, the enzyme of phosphopaluvathydrate stimulates the cleavage of water from the atom C, that is, the process of elimination from the 2-phosphoglycerat molecule and the formation of phosphoenolpiruvat (phosphoenolpirogradic acid).

10th and last step. Transfer phosphate residue with FEP on ADP

In the final reaction of glycolysis, coenzymes - potassium, magnesium and manganese are involved, the fir-catalyst is the catalyst.

The conversion of an enol form of peyrogradic acid in a keto form is a reversible process, and both isomers are present in cells. The process of transition isometric substances from one to another is called tautomerization.

What is anaerobic glycoliz?

Along with aerobic glycoliz, it is the splitting of glucose with the participation of O2, there is a so-called anaerobic glucose decay, in which oxygen does not participate. It also consists of ten consecutive reactions. But where the anaerobic glycilation stage flows, whether it is associated with the processes of oxygen cleavage of glucose, or this is an independent biochemical process, we will try to figure it out.

Anaerobic glycoliz is the decay of glucose in the absence of oxygen with the formation of lactate. But in the process of formation of lactic acid, it does not accumulate in the cell. This process is carried out in those tissues and cells that are functioning under oxygen starvation conditions - hypoxia. Such fabrics primarily include skeletal muscles. In red blood cells, despite the presence of oxygen, lactate is also formed in the process of glycolysis, because there are no mitochondria in blood cells.

Anaerobic hydrolysis occurs in the cytosole (liquid part of the cytoplasm) cells and is the only act producing and supplying ATP, since in this case the oxidative phosphorylation does not work. For oxidative processes, oxygen is needed, and there is no in anaerobic glycolysis.

And peer-grade, and the lactic acids serve as energy sources, to perform certain problems with muscles. Surplus acids come into the liver, where under the action of enzymes are again converted into glycogen and glucose. And the process begins again. The lack of glucose is filled with nutrition - the use of sugar, sweet fruits, and other sweets. So it is impossible to ask the Figure to completely abandon sweet. Sugarozes are needed by the body, but in moderation.

Anaerobic glycoliz is a complex enzymatic process of glucose conversion transformations flowing in human tissues and animals without oxygen consumption (Fig.28).

The reversible conversion of peer-grade acid into the milk catalyzed by lactate dehydrogenase:

The total result of glycolysis is expressed by the following equation: from 6 H 12 O 6 + 2N 3 PO 4 + 2ADF \u003d 2C 3N 6 O 3 + 2AF + 2N 2

Thus, the net yield of ATP with anaerobic glycolize is 2 mol ATP per 1 mol glucose. It is due to the anaerobic glycolisis that the human and animal organism can have a certain period of time to carry out a number of physiological functions in the conditions of oxygen deficiency.

This process in bacteria is called lactic acid fermentation: it underlies the preparation of fermented milk products. Anaerobic glycoliz flows in cytosol cells, where all the necessary enzymes are contained, and does not need a mitochondrial respiratory chain. ATP in the anaerobic glycolysis process is formed by reactions of substrate phosphorylation.

In the yeast in anaerobic conditions there is a similar process - alcohol fermentation, in this case, peyrograde acid is decarboxylated with the formation of acetic aldehyde, which is then restored to ethyl alcohol:

CH 3 -Co-coxy → CH 3 -Cly + CO 2;

CH 3 -Cly + OUN. N + H + → CH 3 -CH 2 -He + Over +.

Fig.28. Glucose anaerobic glycolyising scheme

10.6. Aerobic glucose decay

The aerobic glucose decay includes three stages:

1) Transformation of glucose to peer-grade acid (pyruvate) - aerobic glycoliz. This part is similar to the anaerobic glycolysis discussed above, with the exception of its last stage (transformation of pyruvate into lactic acid);

2) the common catabolism path;

3) The mitochondrial electron transfer circuit is the process of tissue respiration.

Common path of catabolism

The general path of catabolism will comprehend from two stages.

The 1st stage is the oxidative decarboxylation of peeling acid. This is a complex multistage process catalyzed by a multimenzing system - a pyruvate dehydrogenase complex; Localizes in mitochondria (inner membrane and matrix) and can be expressed by the total general scheme:

CH 3 -Co-coxy + HS-Koa + Over + → CH 3 -CO-SKOA + OUN. N + H + + CO 2.

The 2nd stage is the Krebs cycle (citrate cycle, or cycle of tricarboxylic and dicarboxylic acids) (Fig. 29); Localizes in mitochondria (in the matrix). In this cycle, acetyl residue included in acetyl-economy forms a range of primary hydrogen donors. Next, hydrogen with the participation of dehydrogenase enters the breathing chain. As a result of the conjugate action of the citrate cycle and the respiratory chain, acetyl residue is oxidized to CO 2 and H 2 O. The total equation of the entire sequence of glucose transformations during the aerobic decay as follows:

C 6H 12 O 2 + 6O 2 → 6SO 2 + 6N 2

The energy effect of aerobic decay is the synthesis of 38 ATP molecules when splitting 1 glucose molecules. Thus, in the energy relationship, the total oxidation of glucose to carbon dioxide and water is a more efficient process than anaerobic glycoliz. Oxygen slows down anaerobic glycoliz, so in the presence of an excess oxygen, there is a transition in plant and animal tissues from anaerobic glycolysis (fermentation) to breathing (aerobic glycolysis), i.e. Switching cells to a more efficient and economical way to obtain energy (pasteur effect). The role of anaerobic glycolysis in providing the body of energy is especially large in short-term intensive work, when the power of the oxygen transport mechanism towards mitochondria is not enough to provide aerobic glycolysis. So, running for ~ 30 seconds (200 m) is fully provided with anaerobic glycolism, while the speed of anaerobic glycolysis with breathing increase decreases, and the speed of the aerobic decay increases. 4-5 min. Run (1.5 km) - half of energy gives anaerobic, half an aerobic process. After 30 minutes. (10 km running) - Energy is supplied by almost the entire aerobic process.

Erythrocytes do not have mitochondria at all, and their need for ATP is fully satisfied due to anaerobic glycolysis.