1. Can photo- and chemosynthetic organisms get energy from organic oxidation? Of course they can. Plants and chemosynthetics are characterized by oxidation, because they need energy! However, autotrophs will oxidize those substances that they themselves have synthesized.

2. Why do aerobic organisms oxygen? What is the role of biological oxidation? Oxygen is final electron acceptor that come from higher energy levels of oxidizable substances. During this process electrons release a significant amount of energy, and the role of oxidation is precisely in this! Oxidation is the loss of electrons or a hydrogen atom, reduction is their addition.

3. What is the difference between combustion and biological oxidation? As a result of combustion, all energy is completely released in the form heat. But with oxidation, everything is more complicated: only 45 percent of the energy is also released in the form of heat and is spent to maintain normal body temperature. But 55 percent - in the form of ATP energy and other biological batteries. Therefore, most of the energy still goes to create high energy connections.

Stages of energy metabolism

1. Preparatory stage characterized breaking down polymers into monomers(polysaccharides are converted to glucose, proteins to amino acids), fats to glycerol and fatty acids. At this stage, a certain amount of energy is released in the form of heat. The process takes place in the cell lysosomes, at the level of the organism - in digestive system. That is why after the start of the process of digestion, the body temperature rises.

2. glycolysis, or anoxic stage- incomplete oxidation of glucose occurs.

3. oxygen stage- the final breakdown of glucose.

glycolysis

1. glycolysis takes place in the cytoplasm. Glucose C 6 H 12 ABOUT 6 cleaved to PVC (pyruvic acid) C 3 H 4 ABOUT 3 - into two three-carbon PVC molecules. There are 9 different enzymes involved here.

1) At the same time, two PVC molecules have 4 hydrogen atoms less than glucose C 6 H 12 O 6, C 3 H 4 O 3 - PVC (2 molecules - C 6 H 8 O 6).

2) Where are 4 hydrogen atoms spent? Due to 2 atoms 2 NAD+ atoms are reduced to two NADH. Due to the other 2 hydrogen atoms, PVC can turn into lactic acid C 3 H 6 ABOUT 3 .

3) And due to the energy of electrons transferred from high energy levels of glucose to a lower level of NAD +, 2 ATP molecules from ADP and phosphoric acid.

4) Part of the energy is wasted in the form heat.

2. If there is no oxygen in the cell, or there is not enough of it, then 2 PVC molecules are restored due to two NADH to lactic acid: 2C 3 H 4 O 3 + 2NADH + 2H + \u003d 2C 3 H 6 O 3 (lactic acid) + 2HAD +. The presence of lactic acid causes muscle pain during exercise and lack of oxygen. After an active load, the acid is sent to the liver, where hydrogen is split off from it, that is, it turns back into PVC. This PVC can go into the mitochondria for complete breakdown and the formation of ATP. Part of the ATP is also used to convert most of the PVC back into glucose by reversing glycolysis. Blood glucose will go to the muscles and be stored as glycogen.

3. As a result anoxic oxidation of glucose is created in total 2 ATP molecules.

4. If the cell already has, or begins to enter it oxygen, PVC can no longer be restored to lactic acid, but is sent to the mitochondria, where it is completely oxidation to CO 2 AndH 2 ABOUT.

Fermentation

1. Fermentation- this is an anaerobic (oxygen-free) metabolic breakdown of molecules of various nutrients, such as glucose.

2. Alcoholic, lactic, butyric, acetic fermentation takes place under anaerobic conditions in the cytoplasm. Essentially how the process of fermentation corresponds to glycolysis.

3. Alcoholic fermentation is specific for yeast, some fungi, plants, bacteria, which in anoxic conditions switch to fermentation.

4. To solve problems, it is important to know that in each case, during fermentation, glucose is released from glucose 2 ATP, alcohol, or acids- oil, vinegar, milk. During alcoholic (and butyric) fermentation, not only alcohol, ATP, but also carbon dioxide are released from glucose.

Oxygen stage of energy metabolism includes two stages.

1. Tricarboxylic acid cycle (Krebs cycle).

2. Oxidative phosphorylation.

energy exchange(catabolism, dissimilation) - a set of reactions of splitting organic substances, accompanied by the release of energy. The energy released during the breakdown of organic substances is not immediately used by the cell, but is stored in the form of ATP and other high-energy compounds. ATP is the universal energy source of the cell. ATP synthesis occurs in the cells of all organisms in the process of phosphorylation - the addition of inorganic phosphate to ADP.

At aerobic organisms (living in an oxygen environment) distinguish three stages of energy metabolism: preparatory, oxygen-free oxidation and oxygen oxidation; at anaerobic organisms (living in an oxygen-free environment) and aerobic organisms with a lack of oxygen - two stages: preparatory, oxygen-free oxidation.

Preparatory stage

It consists in the enzymatic breakdown of complex organic substances to simple ones: protein molecules - to amino acids, fats - to glycerol and carboxylic acids, carbohydrates - to glucose, nucleic acids - to nucleotides. The breakdown of high-molecular organic compounds is carried out either by enzymes of the gastrointestinal tract or by enzymes of lysosomes. All the released energy is dissipated in the form of heat. The resulting small organic molecules can be used as "building material" or can be further broken down.

Anoxic oxidation, or glycolysis

This stage consists in the further splitting of organic substances formed during the preparatory stage, occurs in the cytoplasm of the cell and does not need the presence of oxygen. The main source of energy in the cell is glucose. The process of oxygen-free incomplete breakdown of glucose - glycolysis.

The loss of electrons is called oxidation, the acquisition is called reduction, while the electron donor is oxidized, the acceptor is reduced.

It should be noted that biological oxidation in cells can occur both with the participation of oxygen:

A + O 2 → AO 2,

and without his participation, due to the transfer of hydrogen atoms from one substance to another. For example, substance "A" is oxidized at the expense of substance "B":

AN 2 + B → A + BH 2

or due to electron transfer, for example, ferrous iron is oxidized to trivalent:

Fe 2+ → Fe 3+ + e -.

Glycolysis is a complex multi-step process that includes ten reactions. During this process, glucose dehydrogenation occurs, the coenzyme NAD + (nicotinamide adenine dinucleotide) serves as a hydrogen acceptor. As a result of a chain of enzymatic reactions, glucose is converted into two molecules of pyruvic acid (PVA), while a total of 2 ATP molecules and a reduced form of the hydrogen carrier NAD H 2 are formed:

C 6 H 12 O 6 + 2ADP + 2H 3 RO 4 + 2NAD + → 2C 3 H 4 O 3 + 2ATP + 2H 2 O + 2NAD H 2.

The further fate of PVC depends on the presence of oxygen in the cell. If there is no oxygen, yeast and plants undergo alcoholic fermentation, in which acetaldehyde is first formed, and then ethyl alcohol:

1. C 3 H 4 O 3 → CO 2 + CH 3 SON,
2. CH 3 SON + NAD H 2 → C 2 H 5 OH + OVER +.

In animals and some bacteria, with a lack of oxygen, lactic acid fermentation occurs with the formation of lactic acid:

C 3 H 4 O 3 + NAD H 2 → C 3 H 6 O 3 + OVER +.

As a result of glycolysis of one glucose molecule, 200 kJ are released, of which 120 kJ is dissipated in the form of heat, and 80% is stored in ATP bonds.

Oxygen oxidation, or respiration

It consists in the complete breakdown of pyruvic acid, occurs in mitochondria and with the obligatory presence of oxygen.

Pyruvic acid is transported to mitochondria (the structure and functions of mitochondria - lecture No. 7). Here, dehydrogenation (hydrogen elimination) and decarboxylation (carbon dioxide elimination) of PVC take place with the formation of a two-carbon acetyl group, which enters into a cycle of reactions called the Krebs cycle reactions. There is further oxidation associated with dehydrogenation and decarboxylation. As a result, three molecules of CO 2 are removed from the mitochondrion for each destroyed PVC molecule; five pairs of hydrogen atoms are formed associated with carriers (4NAD H 2, FAD H 2), as well as one ATP molecule.

The overall reaction of glycolysis and destruction of PVC in mitochondria to hydrogen and carbon dioxide is as follows:

C 6 H 12 O 6 + 6H 2 O → 6CO 2 + 4ATP + 12H 2.

Two ATP molecules are formed as a result of glycolysis, two - in the Krebs cycle; two pairs of hydrogen atoms (2NADHH2) were formed as a result of glycolysis, ten pairs - in the Krebs cycle.

The last step is the oxidation of hydrogen pairs with the participation of oxygen to water with simultaneous phosphorylation of ADP to ATP. Hydrogen is transferred to three large enzyme complexes (flavoproteins, coenzymes Q, cytochromes) of the respiratory chain located in the inner membrane of mitochondria. Electrons are taken from hydrogen, which are eventually combined with oxygen in the mitochondrial matrix:

O 2 + e - → O 2 -.

Protons are pumped into the intermembrane space of mitochondria, into the "proton reservoir". The inner membrane is impermeable to hydrogen ions, on the one hand it is charged negatively (due to O 2 -), on the other - positively (due to H +). When the potential difference across the inner membrane reaches 200 mV, protons pass through the channel of the ATP synthetase enzyme, ATP is formed, and cytochrome oxidase catalyzes the reduction of oxygen to water. So, as a result of the oxidation of twelve pairs of hydrogen atoms, 34 ATP molecules are formed.

The primary source of energy for organisms is the sun. Light quanta are absorbed by chlorophyll contained in the chloroplasts of green plant cells and accumulate in the form of the energy of chemical bonds of organic substances - products of photosynthesis. Heterotrophic cells of plants and animals receive energy from various organic substances (carbohydrates, fats and proteins) synthesized by autotrophic cells. Living beings that can use light energy are called phototrophs, and the energy of chemical bonds - chemotrophs.

The process of consuming energy and matter is called food. There are two types of nutrition: holozoic - by trapping food particles inside the body and holophytic - without capture, through the absorption of dissolved nutrients through the surface structures of the body. Nutrients that enter the body are involved in metabolic processes. Breathing can be called a process in which the oxidation of organic substances leads to the release of energy. Internal, tissue or intracellular respiration occurs in cells. Most organisms are characterized aerobic respiration, which requires oxygen (Fig. 8.4). At anaerobes, living in an environment deprived of oxygen (bacteria), or aerobes with its deficiency, dissimilation proceeds according to the type fermentation(anaerobic respiration). The main substances that break down during respiration are carbohydrates - a reserve of the first order. Lipids represent a reserve of the second order, and only when the reserves of carbohydrates and lipids are exhausted, proteins are used for respiration - a reserve of the third order. In the process of respiration, electrons are transferred through a system of interconnected carrier molecules: the loss of electrons by a molecule is called oxidation, attachment of electrons to a molecule (acceptor) - recovery, the energy released in this case is stored in macroergic bonds of the ATP molecule. One of the most common acceptors in biosystems is oxygen. Energy is released in small portions, mainly in the electron transport chain.

energy exchange, or dissimilation, is a set of reactions of splitting organic substances, accompanied by the release of energy. Depending on the habitat, a single process of energy metabolism can be conditionally divided into several successive stages. In most living organisms - aerobes living in an oxygen environment, three stages are carried out during dissimilation: preparatory, oxygen-free and oxygen, during which organic substances decompose to inorganic compounds.

Rice. 8.4.

First step. IN In the digestive system of multicellular organic food substances, under the action of the corresponding enzymes, they are broken down into simple molecules: proteins - into amino acids, polysaccharides (starch, glycogen) - into monosaccharides (glucose), fats - into glycerol and fatty acids, nucleic acids - into nucleotides, etc. . In unicellular, intracellular cleavage occurs under the action of hydrolytic enzymes of lysosomes. IN during digestion, a small amount of energy is released, which is dissipated in the form of heat, and the formed small organic molecules can undergo further splitting (dissimilation) or be used by the cell as a “building material” for the synthesis of its own organic compounds (assimilation).

Second phase- anoxic, or fermentation, is carried out in the cytoplasm of the cell. The substances formed at the preparatory stage - glucose, amino acids, etc. - undergo further enzymatic decomposition without the use of oxygen. The main source of energy in the cell is glucose. Oxygen-free, incomplete breakdown of glucose (glycolysis) is a multi-stage process of glucose breakdown to pyruvic acid (P V K), and then to lactic, acetic, butyric acids or ethyl alcohol, occurring in the cytoplasm of the cell. During the reactions of glycolysis, a large amount of energy is released - 200 kJ / mol. Part of this energy (60%) is dissipated as heat, the rest (40%) is used for ATP synthesis. The products of glycolysis are pyruvic acid, hydrogen in the form of NADH (nicotinamide adenine dinucleotide) and energy in the form of ATP.

The overall reaction of glycolysis is as follows:

With different types of fermentation, the further fate of glycolysis products is different. In animal cells experiencing a temporary lack of oxygen, for example, in human muscle cells during excessive physical exertion, as well as in some bacteria, lactic acid fermentation occurs, in which PVC is reduced to lactic acid:

The well-known lactic acid fermentation (during the souring of milk, the formation of sour cream, kefir, etc.) is caused by lactic acid fungi and bacteria. During alcoholic fermentation (plants, some fungi, brewer's yeast), the products of glycolysis are ethyl alcohol and CO2. In other organisms, the fermentation products may be butyl alcohol, acetone, acetic acid, etc.

Third stage energy metabolism - complete oxidation, or aerobic respiration, occurs in mitochondria. During the tricarboxylic acid cycle (Krebs cycle), CO 2 is cleaved from PVA, and the two-carbon residue is attached to the coenzyme A molecule to form acetyl coenzyme A, in the molecule of which energy is stored

(acetyl-CoA is also formed during the oxidation of fatty acids and some amino acids). In the subsequent cyclic process (Fig. 8.4), interconversions of organic acids occur, as a result, from one molecule of acetyl coenzyme A, two CO2 molecules, four pairs of hydrogen atoms carried by NADH 2 and FADH 2 (flavin adenine dinucleotide), and two ATP molecules are formed. Electron carrier proteins play an important role in further oxidation processes. They transport hydrogen atoms to the inner mitochondrial membrane, where they are passed along a chain of proteins built into the membrane. The transport of particles along the transport chain is carried out in such a way that protons remain on the outer side of the membrane and accumulate in the intermembrane space, turning it into an H + reservoir, and electrons are transferred to the inner surface of the inner mitochondrial membrane, where they are ultimately combined with oxygen:

As a result, the inner membrane of mitochondria is negatively charged from the inside, and positively from the outside. When the potential difference across the membrane reaches a critical level (200 mV), positively charged H+ particles begin to push through the ATPase channel (an enzyme built into the inner mitochondrial membrane) by the force of the electric field and, once on the inner surface of the membrane, interact with oxygen, forming water. The process at this stage involves oxidative phosphorylation- addition of inorganic phosphate to ADP and the formation of ATP. Approximately 55% of the energy is stored in the chemical bonds of ATP, and 45% is dissipated as heat.

Total reactions of cellular respiration:

The energy released during the breakdown of organic substances is not immediately used by the cell, but is stored in the form of high-energy compounds, usually in the form of adenosine triphosphate (ATP). By its chemical nature, ATP belongs to mononucleotides and consists of a nitrogenous base of adenine, a ribose carbohydrate and three phosphoric acid residues, interconnected by macroergic bonds (30.6 kJ).

The energy released during ATP hydrolysis is used by the cell to perform chemical, osmotic, mechanical and other types of work. ATP is the universal energy source of the cell. The supply of ATP in the cell is limited and replenished due to the process of phosphorylation, which occurs at different rates during respiration, fermentation and photosynthesis.

Anchor points

• Metabolism consists of two closely interconnected and oppositely directed processes: assimilation and dissimilation.
• The vast majority of life processes occurring in the cell require energy in the form of ATP.
• The breakdown of glucose in aerobic organisms, in which the anoxic step is followed by the breakdown of lactic acid with the participation of oxygen, is 18 times more energy efficient than anaerobic glycolysis.

Questions and tasks for repetition

• 1. What is dissimilation? Describe the steps in this process. What is the role of ATP in cell metabolism?
• 2. Tell us about the energy metabolism in the cell using the breakdown of glucose as an example.
• 3. What organisms are called heterotrophic? Give examples.
• 4. Where, as a result of what transformations of molecules and in what quantity is ATP formed in living organisms?
• 5. What organisms are called autotrophic? What groups are autotrophs divided into?

Alcoholic fermentation underlies the preparation of any alcoholic beverage. This is the easiest and most affordable way to get ethyl alcohol. The second method - ethylene hydration, is synthetic, rarely used and only in the production of vodka. We will look at the features and conditions of fermentation to better understand how sugar is converted to alcohol. From a practical point of view, this knowledge will help to create the optimal environment for yeast - to put mash, wine or beer correctly.

Alcoholic fermentation Yeast converts glucose into ethyl alcohol and carbon dioxide in an anaerobic (oxygen-free) environment. The equation is the following:

C6H12O6 → 2C2H5OH + 2CO2.

As a result, one molecule of glucose is converted into 2 molecules of ethyl alcohol and 2 molecules of carbon dioxide. In this case, energy is released, which leads to a slight increase in the temperature of the medium. Fusel oils are also formed during the fermentation process: butyl, amyl, isoamyl, isobutyl and other alcohols, which are by-products of amino acid metabolism. In many ways, fusel oils form the aroma and taste of the drink, but most of them are harmful to the human body, so manufacturers try to purify alcohol from harmful fusel oils, but leave useful ones.

Yeast- These are single-celled spherical fungi (about 1500 species), actively developing in a liquid or semi-liquid medium rich in sugars: on the surface of fruits and leaves, in the nectar of flowers, dead phytomass and even soil.

Yeast cells under a microscope

This is one of the very first organisms "tamed" by man, mainly yeast is used for baking bread and making alcoholic beverages. Archaeologists have found that the ancient Egyptians for 6000 years BC. e. learned how to make beer, and by 1200 BC. e. mastered the baking of yeast bread.

The scientific study of the nature of fermentation began in the 19th century, the first chemical formula was proposed by J. Gay-Lussac and A. Lavoisier, but the essence of the process remained unclear, two theories arose. The German scientist Justus von Liebig suggested that fermentation is mechanical in nature - the vibrations of the molecules of living organisms are transmitted to sugar, which is split into alcohol and carbon dioxide. In turn, Louis Pasteur believed that the basis of the fermentation process is biological in nature - when certain conditions are reached, the yeast begins to process sugar into alcohol. Pasteur managed to prove his hypothesis empirically, later the biological nature of fermentation was confirmed by other scientists.

The Russian word “yeast” comes from the Old Slavonic verb “drozgati”, which means “to crush” or “knead”, there is a clear connection with baking bread. In turn, the English name for yeast "yeast" comes from the Old English words "gist" and "gyst", which mean "foam", "to give off gas" and "boil", which is closer to distillation.

As a raw material for alcohol, sugar, sugar-containing products (mainly fruits and berries), as well as starch-containing raw materials: grain and potatoes are used. The problem is that yeast cannot ferment starch, so you first need to break it down to simple sugars, this is done by an enzyme called amylase. Amylase is found in malt, a germinated grain, and is activated at high temperature (usually 60-72 ° C), and the process of converting starch to simple sugars is called "saccharification". Saccharification with malt ("hot") can be replaced by the introduction of synthetic enzymes, in which the wort does not need to be heated, therefore the method is called "cold" saccharification.

Fermentation conditions

The following factors influence the development of yeast and the course of fermentation: sugar concentration, temperature and light, acidity of the environment and the presence of trace elements, alcohol content, oxygen access.

1. Sugar concentration. For most yeast races, the optimal sugar content of the wort is 10-15%. At concentrations above 20%, fermentation weakens, and at 30-35% it is almost guaranteed to stop, since sugar becomes a preservative that prevents yeast from working.

Interestingly, when the sugar content of the medium is below 10%, fermentation also proceeds poorly, but before sweetening the wort, you need to remember the maximum concentration of alcohol (4th point) obtained during fermentation.

2. Temperature and light. For most yeast strains, the optimum fermentation temperature is 20-26°C (bottom-fermenting brewer's yeast requires 5-10°C). The allowable range is 18-30 °C. At lower temperatures, fermentation slows down significantly, and at values ​​below zero, the process stops and the yeast “falls asleep” - falls into suspended animation. To resume fermentation, it is enough to raise the temperature.

Too high a temperature will kill the yeast. The threshold of endurance depends on the strain. In general, values ​​above 30-32 °C are considered dangerous (especially for wine and beer), however, there are separate races of alcohol yeast that can withstand wort temperatures up to 60 °C. If the yeast is “cooked”, you will have to add a new batch to the wort to resume fermentation.

The fermentation process itself causes a temperature increase of several degrees - the larger the volume of the wort and the more active the yeast, the stronger the heating. In practice, temperature correction is done if the volume is more than 20 liters - it is enough to keep the temperature below 3-4 degrees from the upper limit.

The container is left in a dark place or covered with a thick cloth. The absence of direct sunlight avoids overheating and has a positive effect on the work of yeast - fungi do not like sunlight.

3. Acidity of the environment and the presence of trace elements. Medium acidity 4.0-4.5 pH promotes alcoholic fermentation and inhibits the development of third-party microorganisms. In an alkaline environment, glycerol and acetic acid are released. In neutral wort, fermentation proceeds normally, but pathogenic bacteria actively develop. The acidity of the wort is corrected before adding the yeast. Often, amateur distillers increase the acidity with citric acid or any acidic juice, and to reduce the must, they quench the must with chalk or dilute it with water.

In addition to sugar and water, yeast requires other substances - primarily nitrogen, phosphorus and vitamins. These trace elements are used by yeast for the synthesis of amino acids that make up their protein, as well as for reproduction at the initial stage of fermentation. The problem is that at home it will not be possible to accurately determine the concentration of substances, and exceeding the permissible values ​​\u200b\u200bcan negatively affect the taste of the drink (especially for wine). Therefore, it is assumed that starch-containing and fruit raw materials initially contain the required amount of vitamins, nitrogen and phosphorus. Usually only pure sugar mash is fed.

4. Alcohol content. On the one hand, ethyl alcohol is a waste product of yeast, on the other hand, it is a strong toxin for yeast fungi. At an alcohol concentration in the wort of 3-4%, fermentation slows down, ethanol begins to inhibit the development of yeast, at 7-8% the yeast no longer reproduces, and at 10-14% they stop processing sugar - fermentation stops. Only a few strains of cultured yeast, bred in the laboratory, are tolerant of alcohol concentrations above 14% (some continue to ferment even at 18% and above). About 0.6% alcohol is obtained from 1% sugar in the wort. This means that to obtain 12% alcohol, a solution with a sugar content of 20% (20 × 0.6 = 12) is required.

5. Access to oxygen. In an anaerobic environment (without access to oxygen), yeast is aimed at survival, not reproduction. It is in this state that the maximum alcohol is released, so in most cases it is necessary to protect the wort from air access and at the same time organize the removal of carbon dioxide from the tank in order to avoid increased pressure. This problem is solved by installing a water seal.

With constant contact of the wort with air, there is a danger of souring. At the very beginning, when fermentation is active, the released carbon dioxide pushes air away from the surface of the wort. But at the end, when fermentation weakens and less and less carbon dioxide appears, air enters the uncovered container with the wort. Under the influence of oxygen, acetic acid bacteria are activated, which begin to process ethyl alcohol into acetic acid and water, which leads to spoilage of wine, a decrease in the yield of moonshine and the appearance of a sour taste in drinks. Therefore, it is so important to close the container with a water seal.

However, yeast requires oxygen to multiply (to reach its optimal amount). Usually, the concentration that is in the water is enough, but for accelerated reproduction of the mash, after adding the yeast, it is left open for several hours (with air access) and mixed several times.

Par.22 In the cells of which organisms does alcoholic fermentation occur? In most plant cells, as well as in the cells of some fungi (for example, yeast), instead of glycolysis, alcoholic fermentation occurs; under anaerobic conditions, the glucose molecule is converted into ethyl alcohol and CO2. Where does the energy come from to synthesize ATP from ADP? It is released in the process of dissimilation, i.e., in the reactions of splitting organic substances in the cell. Depending on the specifics of the organism and the conditions of its habitat, dissimilation can take place in two or three stages. What are the stages in energy metabolism? 1 - preparatory; concluding in the breakdown of large organic molecules to simpler ones: polys.-monoses., lipids-glyc.and fat. acids, proteins-a.k. Cleavage occurs in PS. Little energy is released, while it is dissipated in the form of heat. The resulting compounds (monosacs, fatty acids, a.k., etc.) can be used by the cell in formation exchange reactions, as well as for further expansion in order to obtain energy. 2- anoxic = glycolysis (an enzymatic process of sequential breakdown of glucose in cells, accompanied by the synthesis of ATP; under aerobic conditions leads to the formation of pyruvic acid, under anaerobic conditions leads to the formation of lactic acid); С6Н12О6 + 2Н3Р04 + 2ADP --- 2С3Н6О3 + 2ATP + 2Н2О. consists in the enzymatic decomposition of org.vest-in, which were obtained during the preparatory stage. O2 does not participate in the reactions of this stage. Glycolysis reactions are catalyzed by many enzymes and take place in the cytoplasm of cells. 40% of the energy is stored in ATP molecules, 60% is dissipated as heat. Glucose breaks down not to end products (CO2 and H2O), but to compounds that are still rich in energy and, oxidized further, can give it in large quantities (lactic acid, ethyl alcohol, etc.). 3- oxygen (cellular respiration); organic substances formed during stage 2 and containing large reserves of chemical energy are oxidized to the final products CO2 and H2O. This process takes place in the mitochondria. As a result of cellular respiration, during the breakdown of two molecules of lactic acid, 36 ATP molecules are synthesized: 2C3H6O3 + 6O2 + 36ADP + 36H3PO4 - 6CO2 + 42H2O + 36ATP. A large amount of energy is released, 55% is stored in the form of ATP, 45% is dissipated in the form of heat. What is the difference between energy metabolism in aerobes and anaerobes? Most of the living creatures that live on Earth are aerobes, i.e. used in the processes of RH O2 from the environment. In aerobes, energy exchange occurs in 3 stages: preparation, oxygen-free and oxygen. As a result of this, organic matter decomposes to the simplest inorganic compounds. In organisms that live in an oxygen-free environment and do not need oxygen - anaerobes, as well as in aerobes with a lack of oxygen, assimilation occurs in two stages: preparatory and oxygen-free. In the two-stage version of the energy exchange, much less energy is stored than in the three-stage one. TERMS: Phosphorylation is the attachment of 1 phosphoric acid residue to an ADP molecule. Glycolysis is an enzymatic process of sequential breakdown of glucose in cells, accompanied by the synthesis of ATP; under aerobic conditions leads to the formation of pyruvic acid, into anaerobic. conditions leads to the formation of lactic acid. Alcoholic fermentation is a fermentation chemical reaction as a result of which a glucose molecule under anaerobic conditions turns into ethyl alcohol and CO2 Par.23 Which organisms are heterotrophs? Heterotrophs - organisms that are not able to synthesize organic substances from inorganic ones (living, fungi, many bacteria, plant cells, not able to photosynthesis) What organisms on Earth practically do not depend on the energy of sunlight? Chemotrophs - use for the synthesis of organic substances the energy released during the chemical transformations of inorganic compounds. TERMS: Nutrition - a set of processes that include the intake, digestion, absorption and assimilation of nutrients by the body. In the process of nutrition, organisms receive chemical compounds that they use for all life processes. Autotrophs are organisms that synthesize organic compounds from inorganic ones, receiving carbon from the environment in the form of CO2, water and mineral salts. Heterotrophs - organisms that are not able to synthesize organic substances from inorganic ones (live, fungi, many bacteria, plant cells, not able to photosynthesis)