In which organs does the formation of organic substances occur? Oxidation of organic substances and compounds: reaction process and final products of formation

Under the conditions of modern Earth, the natural formation of organic compounds from inorganic ones practically does not occur. Moreover, the emergence of living organic matter is impossible. As for the early Earth, the conditions on it were completely different. A reducing atmosphere with a high concentration of hydrogen, methane and ammonia, intense ultraviolet radiation from the Sun, not absorbed by such an atmosphere, and powerful electrical discharges in the atmosphere created the necessary and, apparently, sufficient conditions for the formation of organic compounds. Indeed, laboratory experiments carried out under conditions simulating the supposed atmosphere of the early Earth have produced a number of organic compounds, including amino acids that are part of living proteins.

The absence of oxygen in the atmosphere was a necessary condition for the spontaneous synthesis of organic matter. However, from the point of view of subsequent transformations, this factor turned out to be destructive. In fact, the oxygen-deprived atmosphere almost freely transmits powerful ultraviolet radiation (the atmosphere of the modern Earth has an ozone layer that arose along with the oxygen component, which absorbs this radiation). Radiation, while providing energy for the chemical reactions of the synthesis of organic compounds, at the same time tends to immediately destroy them. Therefore, biopolymers, lipids and hydrocarbons formed in the atmosphere, as soon as they emerged, were doomed. In order not to die, they needed to hide from the harmful effects of solar ultraviolet radiation. It is believed that some of these organic compounds escaped destruction by entering the aquatic environment of primary reservoirs.

Here, in an aqueous environment, organic compounds entered into a variety of chemical reactions, among which the reactions that led to the self-development of the most active catalysts took advantage. Nature very strictly pursued the natural selection of cyclic reactions capable of self-sustaining, including due to the energy released during the reaction. The problem of energy supply for evolutionary reactions, in particular polymerization reactions (the combination of molecules of the same type - monomers into macromolecules) seems to be the most important at this stage of evolution, since the aqueous environment contributes little to the activation of chemical reactions. That is why only high-energy reactions involving particularly effective, self-developing catalysts could “survive.”

Here came one of the key moments of development. Let us assume that the chemical reactions necessary for the transition to bioevolution arose and acquired the property of self-sustaining. For their preservation (and, of course, further development), the corresponding volumes must be somehow isolated from the unorganized environment, without losing the ability to exchange matter and energy with it. The simultaneous fulfillment of these two, at first glance, incompatible conditions was mandatory for chemical evolution to reach a qualitatively new level.

This opportunity was found due to the formation of special structures from lipids - membrane shells . The results of modern laboratory experiments give reason to believe that at a certain concentration of lipids in water and external conditions simulating the state of the atmosphere and hydrosphere of the then Earth, a characteristic process of self-organization occurs, leading to self-assembly of lipid shells with membrane properties.

Further, it is not difficult to assume that the processes of selection of cyclic catalytic reactions and self-assembly of lipid shells coincided in time and space. Thus, natural formations could well have appeared, isolated from the destructive influence of the environment, but connected with it by metabolism. Self-sustaining reactions began to occur in a kind of reactor, which helps maintain the significant nonequilibrium of the biopolymer system contained in it. Now the position of the chemical reagents has become orderly, adsorption processes on the shell contributed to an increase in their concentration and, thereby, activation of the catalytic effect. In fact, it took place transition from chemical mixtures to organized systems adapted to further upward development.

A number of other models are also considered that lead to a similar important, but still intermediate event on the path to the transition to biological evolution. One of them considers the processes associated with the formation of initial organic compounds in the atmosphere, under the assumption that the early Earth with its rarefied reducing atmosphere was a cold body with a temperature of the order of -50°C. An essential point of this model is the assumption that the atmosphere under these conditions was ionized, i.e., was in a state of cold plasma. This plasma is considered the main source of energy for chemical evolution reactions. The assumption of low temperature is used to explain the preservation of biopolymers formed in the atmosphere: freezing, they fell onto the Earth’s ice cover and were stored in this natural refrigerator “until better times.” In this form, ultraviolet radiation and powerful discharges of electricity were no longer so dangerous for them.

It is further assumed that “better times” came with the intensification of tectonic activity and the beginning of massive volcanic eruptions. The release of products of volcanic activity into the atmosphere led to its compaction and a shift of the ionization boundary to higher layers. With a change in temperature conditions, the ice cover naturally melted, primary reservoirs were formed, in which, after defrosting, biopolymers, lipids and hydrocarbons accumulated over a long time began active chemical activity. Therefore, we can talk about their high concentration in "primordial broth"(as the resulting substance is often called), which was another positive factor from the point of view of intensifying chemical evolution.

Repeated experiments have confirmed that during thawing, lipids actually demonstrate self-assembly, forming microspheres with a diameter of tens of micrometers. It doesn’t matter how the biopolymers end up inside them - whether they penetrate through the membrane layer or the lipid shell envelops them gradually. The important thing is that in a volume surrounded by a membrane shell, a new stage of evolution could begin - the transition from chemical reactions to biochemical ones.

As for the decisive moment - the transition to the simplest cell, it can be considered as the result of a jump characteristic of the self-organization of matter. To prepare for this leap, some more structures had to appear in the process of chemical evolution capable of performing the functions necessary for the protocell. Such structural fragments are considered factions , ensuring the transfer of charged particles, which is necessary for the transport of matter. Other groups must provide energy supply - these are mainly molecules of phosphorus-containing compounds (ADP-ATP system). Finally, it is necessary to form polymer structures such as DNA and RNA, the main function of which is to serve catalytic matrix for self-reproduction.

One more key point related to the violation of isomeric symmetry should not be overlooked. How the choice in favor of left-handed organic matter occurred can only be guessed at, but the fact that this fluctuation immediately preceded the origin of life seems completely natural. It can be assumed that biological evolution was “launched” by the emergence of a left-handed protocell.

Federal Agency for Education

State educational institution

Novgorod State University named after. Yaroslav the Wise

Faculty of Science and Natural Resources

Department of Chemistry and Ecology

formation and consumption of organic matter by plants

Collection of guidelines

Velikiy Novgorod

Formation and consumption of organic substances by plants: Collection of guidelines for laboratory work / Compiled by Kuzmina I. A. - NovSU, Veliky Novgorod, 2007. - 12 p.

The guidelines are intended for students of specialty 020801.65 - “Ecology” and all students studying “General Ecology”.

For the formation of organic matter - the basis of plant biomass on Earth - atmospheric carbon dioxide and water are needed, as well as soil minerals. Using light of a certain wavelength, carbon dioxide is fixed in plants during photosynthesis. As a result, oxygen is released into the atmosphere, which is formed during the photolysis of water. This is the first stage of the biochemical carbon cycle.

The amount of energy stored on Earth through photosynthesis is enormous. Every year, as a result of photosynthesis by green plants, 100 billion tons of organic substances are formed, which contain about 450-1015 kcal of solar energy converted into the energy of chemical bonds. These processes are accompanied by phenomena of such grand scale as the assimilation by plants of about 170 billion tons of carbon dioxide, the photochemical decomposition of about 130 billion tons of water, from which 115 billion tons of free oxygen are released.

Oxygen is the basis of life for all living creatures, which use it to oxidize various organic compounds during the process of respiration; stands out CO2. This is the second stage of the biochemical carbon cycle, associated with the carbon dioxide function of living organisms. In this case, the release of oxygen at the first stage is approximately an order of magnitude greater than its absorption at the second stage, as a result of which, during the functioning of green plants, oxygen accumulates in the atmosphere.

The energy bound by autotrophs in the process of photosynthesis is subsequently spent on the vital activity of various heterotrophs, including humans, partially turning into thermal energy, and is stored in a number of components that make up the biosphere (plants and soil). In terrestrial biomes, carbon during photosynthesis is most strongly sequestered by forests (-11 billion tons per year), then arable land (-4 billion tons), steppes (-1.1 billion tons), deserts (-0.2 billion tons ). But most of all carbon is bound by the World Ocean, which occupies about 70% of the Earth's surface (127 billion tons per year).

The resulting organic substances of autotrophs enter the food chains of various heterotrophs and, passing through them, are transformed, lose mass and energy (pyramids of mass, energy), the latter is spent on the vital processes of all organisms that are included as links in the food chains, goes into the world space in the form of thermal energy.

The organic matter of various living organisms, after they die, becomes the property (food) of heterotrophic microorganisms. Microorganisms decompose organic matter through the processes of feeding, respiration and fermentation. When carbohydrates decompose, carbon dioxide is formed, which is released into the atmosphere from terrestrial decomposed organic matter, as well as from the soil. The decomposition of proteins produces ammonia, which is partially released into the atmosphere, and mainly through the process of nitrification replenishes nitrogen reserves in the soil.

Some of the organic matter does not decompose, but forms a “reserve fund”. In prehistoric times, this is how coal, gas, shale were formed, and at present - peat and soil humus.

All of the above processes represent the most important stages and phases of biochemical cycles (carbon, oxygen, nitrogen, phosphorus, sulfur, etc.). Thus, living matter in the process of its metabolism ensures the stability of the existence of the biosphere with a certain composition of air, water, soil, and without human intervention this homeostasis of the Earth ecosystem would be maintained indefinitely.

2 Safety requirements

The experiments are carried out strictly in accordance with the methodological guidelines. When performing work, general safety regulations for chemical laboratories should be followed. If reagents come into contact with skin or clothing, the affected area should be quickly rinsed with plenty of water.

3 Experimental part

Work No. 1. Determination of the formation of organic matter in plant leaves during photosynthesis (based on carbon content)

Photosynthesis is the main process of accumulation of matter and energy on Earth, as a result of which CO2 And H2O organic substances are formed (glucose in this formula):

6СО2 + 6Н2О + light energy → С6Н12О6+ 602t

One way to measure the intensity of photosynthesis is to determine the formation of organic matter in plants by carbon content, which is taken into account by the wet combustion method developed for soils and modified for woody plants by F. 3. Borodulina.

In a sample of leaves, the carbon content is determined, then the leaves are exposed to light for 2-3 hours or more and the carbon content is determined again. The difference between the second and first determination, expressed per unit of leaf surface per unit of time, indicates the amount of organic matter formed.

During the combustion process, the carbon of the leaves is oxidized with a 0.4 N solution of potassium dichromate in sulfuric acid. The reaction proceeds according to the following equation:

2K2Cr2О7 + 8H2SO4 + 3C = 2K2SO4 + 2Cr2(SO4)3 + 8H2O + 3СО2

The unspent amount of potassium bichromate is determined by back titration with 0.2 N solution of Mohr's salt:

6FeSO4 ∙ (NH4)2SO4 + K2Cr2O7 + 7H2SO4 =

Cr2(SO4)3 + 3Fe2(SO4)3 + 6(NH4)2SO4 + K2SO4 + 7H2O

A colorless solution of diphenylamine is used as an indicator, which upon oxidation turns into blue-violet diphenylbenzidine violet. Potassium dichromate oxidizes diphenylamine and the mixture acquires a red-brown color. When titrated with Mohr's salt, hexavalent chromium is reduced to trivalent chromium. As a result, the color of the solution turns blue, and towards the end of the titration it turns blue-violet. When chromium is titrated, the subsequent addition of Mohr's salt causes the oxidized form of the indicator to transform into a reduced (colorless); A green color appears, which is given to the solution by trivalent chromium ions. The clear transition of the blue-violet color to green is hampered by ferric iron ions that appear during the reaction. To make the end of the titration reaction clearer, it is carried out in the presence of orthophosphoric acid, which binds Fe3+ ions into a colorless complex ion 3 and protects diphenylamine from oxidation.

Equipment, reagents, materials:

1) 250 ml conical flasks; 2) heat-resistant conical flasks of 100 ml; 3) small glass funnels used as reflux condensers; 4) burettes; 5) 0.4 N solution of potassium dichromate (in dilute sulfuric acid (1:1)); 6) 0.2 N solution of Mohr's salt; 7) diphenylamine; 8) 85% phosphoric acid; 9) a plug drill or other device for knocking out disks with a diameter of 1 cm; 10) graduated cylinder; 11) vegetative plants with symmetrical wide and thin leaf blades (geranium, fuchsia, leaves of woody plants).

Progress

The leaf of a vegetative plant is divided into two halves along the main vein and 3 disks with a diameter of 1 cm are cut out on one of them using a cork drill, placed on the bottom of a conical heat-resistant flask with a volume of 100 ml, into which 10 ml of a 0.4 N solution of K2Cr2O7 is poured. . The flask is closed with a small funnel with the spout down and placed on an electric stove with a closed spiral in a fume hood. When the solution boils, achieve a gentle boil for 5 minutes, sometimes lightly shaking the flask in a circular motion so that the disks are well covered with liquid. A belt made of several layers of thick paper is placed on the top of the flask (without covering the neck), which will prevent burns to your hands when stirring the contents of the flask and when rearranging it.

Then the flask is removed from the heat, placed on a ceramic tile and cooled. The liquid should be brownish in color. If its color is greenish, then this indicates an insufficient amount of potassium bichromate taken for the oxidation of organic matter. In this case, the determination must be repeated with more reagent or fewer cuts.

150 ml of distilled water is added to the cooled solution in small portions in several stages, then this liquid is gradually poured into a 250 ml flask, into which 3 ml of 85% orthophosphoric acid and 10 drops of diphenylamine are added. Shake the contents and titrate with 0.2 N Mohr's salt solution.

At the same time, a control determination is carried out (without plant material), carefully observing all the above operations. Mohr's salt loses its titer relatively quickly, so the solution must be checked periodically before starting the determination.

The amount of organic matter carbon contained in 1 dm2 of leaf surface is calculated using the formula:

a is the amount of Mohr’s salt in ml used for titration of the control solution;

b is the amount of Mohr’s salt in ml used for titration of the experimental solution;

k - correction to Mohr's salt titer;

0,6 - milligrams of carbon corresponding to 1 ml of exactly 0.2 N solution of Mohr's salt;

S - area of ​​cuttings, cm2.

Results recording scheme

Example of calculating the amount of carbon:

1. At the beginning of the experiment:

a = 19 ml, b = 9 ml, k = 1, S = πr2∙3 = (3.14 ∙ 12) ∙ 3 = 9.4 cm2

Hydrogen" href="/text/category/vodorod/" rel="bookmark">Hydrogen volatilizes in the form of carbon dioxide, water and nitrogen oxides. The remaining non-volatile residue (ash) contains elements called ash. The difference between the mass of the entire dry sample and The ash residue is a mass of organic matter.

1) analytical or precision technochemical balances; 2) muffle furnace; 3) crucible tongs; 4) electric stove with a closed spiral; 5) porcelain crucibles or evaporation cups; 6) dissecting needles; 7) desiccator; 8) alcohol; 9) distilled water; 10) calcium chloride; 11) wood shavings, crushed bark, leaves, humus-rich soil, dried to an absolutely dry mass.

Progress

Dry and crushed samples of wood, bark, leaves, as well as soil (3-6 g or more), selected by the average sample method, are weighed to 0.01 g on tracing paper. They are placed in calcined and weighed porcelain crucibles or evaporation dishes (5-7 cm in diameter), filled with a 1% solution of ferric chloride, which turns brown when heated and does not disappear when heated. Crucibles with organic matter are placed on a heated electric stove in a fume hood and heated until charring and the disappearance of black smoke. Moreover, if there is a larger amount of plant material, it can be supplemented from a pre-weighed sample.

Then the crucibles are placed in a muffle furnace at a temperature of 400-450 ° C and burned for another 20-25 minutes until the ash turns gray-white. At higher calcination temperatures there may be significant losses of sulfur, phosphorus, potassium and sodium. Fusion with silicic acid may also occur, preventing complete ashing. In this case, the calcination is stopped, the crucible is cooled and a few drops of hot distilled water are added to it; dry on a hotplate and continue calcining.

The following ash color options are possible: red-brown (with a high content of iron oxides in the sample), greenish (in the presence of manganese), gray-white.

In the absence of a muffle furnace, combustion can be carried out for educational purposes on an electric stove under traction. To create higher temperatures, it is necessary to protect the tile closely with an iron sheet in the form of a side 5-7 cm high from the tile sheet, and also cover it with a piece of asbestos on top. Combustion lasts 30-40 minutes. When burning, it is necessary to periodically stir the material with a dissecting needle. Incineration is also carried out to white ash.

In the case of slow burning, a small amount of alcohol is poured into cooled crucibles and ignited. There should be no noticeable black coal particles in the ash. Otherwise, the samples are treated with 1 ml of distilled water, stirred and calcination is repeated.

After combustion is completed, the crucibles are cooled in a desiccator with a lid and weighed.

Statement" href="/text/category/vedomostmz/" rel="bookmark">statement drawn on the board.

Results recording scheme

Any community of living organisms on Earth is characterized by its productivity and sustainability. Productivity is defined, in particular, as the difference between the accumulation and consumption of organic matter during such cardinal processes as photosynthesis and respiration. In the first process, organic matter is synthesized from carbon dioxide and water with the release of oxygen, in the second it decomposes due to oxidative processes taking place in the mitochondria of cells with the absorption of oxygen. Different plants vary greatly in the relationship between these processes. Yes, y C4 plants (corn, sorghum, sugar cane, mangroves) have a high intensity of photosynthesis with little light respiration, which ensures their high productivity compared to C3 plants (wheat, rice).

C3 - plants. These are the majority of plants on Earth that carry out C3- a way of fixing carbon dioxide during photosynthesis, resulting in the formation of three-carbon compounds (glucose, etc.). These are mainly plants of temperate latitudes with an optimum temperature of +20...+25°C, and a maximum of +35...+45°C.

C4 - plants. These are those whose fixation products CO2 are four-carbon organic acids and amino acids. This includes mainly tropical plants (corn, sorghum, sugarcane, mangroves). C4- fixation path CO2 is now found in 943 species from 18 families and 196 genera, including a number of cereal plants of temperate latitudes. These plants are distinguished by a very high intensity of photosynthesis and can tolerate high temperatures (their optimum is +35...+45°C, maximum +45...+60°C). They are very adapted to hot conditions, use water efficiently, tolerate stress well - drought, salinity, and are characterized by an increased intensity of all physiological processes, which determines their very high biological and economic productivity.

Aerobic respiration (with the participation of oxygen) is the reverse process of photosynthesis. In this process, organic substances synthesized in cells (sucrose, organic and fatty acids) are decomposed, releasing energy:

С6Н12О6 + 6О2 → 6СО2 + 6Н2О + energy

All plants and animals receive energy to maintain their vital functions through respiration.

The method for determining the respiration rate of plants is based on taking into account the amount of carbon dioxide released by plants, which is absorbed by barite:

Ba(OH)2 + CO2 = BaCO3 + H2O

Excess barite that has not reacted with CO2, titrate with hydrochloric acid:

Ba(OH)2 + 2HCl = BaCl2 + H2O

Equipment, reagents, materials

1) wide-neck conical flasks with a capacity of 250 ml; 2) rubber plugs with drilled holes into which a glass tube is inserted; a thin wire 12-15 cm long is pulled into the tube; 3) technochemical scales; 4) weights; 5) black opaque paper; 6) burettes with a Ba(OH)2 solution and a stopper on top into which a tube with soda lime is inserted; 7) 0.1 N solution of Ba(OH)2; 8) 0.1 N HCI solution; 9) 1% phenolphthalein solution in a dropper; 10) green leaves, freshly picked in the wild or leaves of indoor plants.

Progress

5-8 g of green, freshly picked plant leaves are weighed with petioles on a technochemical scale, the petioles are fastened with one end of a wire, which is pulled through the hole in the cork (Fig. 1).

Rice. 1. Mounted flask for determining respiration intensity:

1 - wire, 2 - glass tube, 3 - rubber stopper, 4 - bunch of leaves, 5 - barite.

It is recommended that you first carry out a test installation by lowering the material into the flask and closing the flask with a stopper. Make sure that the stopper tightly covers the flask, the bunch of leaves is located in the upper part of the flask, and the distance between the barite and the bunch is large enough. It is recommended to seal all the holes between the flask, stopper and tube with plasticine, and insulate the system with a piece of foil at the top exit of the wire from the tube.

10 ml of 0.1 N Ba(OH)2 solution is poured from a burette into the test flasks, the material is placed and isolated using the above method. The control (without plants) is performed in 2-3 times. All flasks are covered with black opaque paper to exclude photosynthesis and the identity of all flasks, the start time of the experiment is noted, which lasts 1 hour. During the experiment, the flasks should be periodically gently rocked to destroy the BaCO3 film that forms on the surface of the barite and prevents the complete absorption of CO2.

After one hour, open the stopper slightly and remove the material from the flasks by quickly pulling out the wire with leaves. Immediately close the stopper, insulating the top of the tube with foil. Before titration, add 2-3 drops of phenolphthalein to each flask: the solution turns crimson. Titrate free barite with 0.1 N HCl. In this case, the control flasks are titrated first. Take the average and then titrate the experimental flasks. Solutions should be titrated carefully until they become discolored. Write the results in a table (on the board and in your notebook).

Final product" href="/text/category/konechnij_produkt/" rel="bookmark">final products

Another form of decomposition of organic matter to the simplest compounds is microbiological processes in soils and waters, which results in the formation of soil humus and various bottom sediments of semi-decomposed organic matter (sapropel, etc.). The main of these processes is the biological decomposition by saprophytes of organic substances containing nitrogen and carbon, which is an integral part of the cycles of these elements in natural cycles. Ammonifier bacteria mineralize proteins from plant and animal residues, as well as other microorganisms (including nitrogen fixers), urea, chitin, and nucleic acids, resulting in the formation of ammonia (NH3). Plant and animal proteins containing sulfur also decompose, resulting in the formation of hydrogen sulfide (H2S). The waste products of microorganisms are indole compounds, which act as growth stimulants. The best known is β-indolylacetic acid or heteroauxin. Indolic substances are formed from the amino acid tryptophan.

The process of decomposition of organic substances into simple compounds is enzymatic. The final stage of ammonification is ammonium salts available to plants.

Equipment, reagents, materials

1) technochemical scales; 2) thermostat; 3) test tubes; 4) cotton plugs; 5) beakers; 6) Petri dishes; 7) NaHCO3; 8) 5% PbNO3 or Pb(CH3COO)2; 9) Salkovsky reagent; 10) Ehrlich's reagent; 11) ninhydrin reagent; 12) Nessler's reagent; 13) humus soil; 14) fresh lupine leaves or dried leaves of other legumes; 15) fish, meat meal or pieces of meat, fish.

Progress

A. Ammonification of animal proteins

a) Place 0.5-1 g of fresh fish or a small piece of meat into a test tube. Add settled water to half the volume of the test tube and 25-50 mg NaHCO3 (at the tip of a scalpel) to neutralize the environment, which favors the activity of ammonifiers (a neutral or slightly alkaline environment at pH = 7 and above is favorable for them). Add a small lump of humus soil to introduce ammonifiers into the medium, mix the contents of the test tube, plug the test tube with a cotton stopper, having previously secured a piece of lead paper between the stopper and the test tube (Fig. 2) so that it does not touch the solution. Wrap each test tube at the top with foil to prevent gas from escaping from the test tube. Place everything in a thermostat at 25-30°C for 7-14 days.

Rice. 2. Mounted test tube for determining protein ammonification: 1 - test tube; 2 - cotton plug; 3 - lead paper; 4 - Wednesday.

This experiment simulates the decomposition of organic residues in the aquatic environment of a standing reservoir (for example, a pond), into which soil particles from adjacent fields can be washed away.

b) Pour humus soil into a glass, pour in settled water, bury a small piece of meat in the soil, strengthen lead paper between the soil and the edge of the glass, close the system with a Petri dish (side down), put in a thermostat at 25-30 ° C for one or two weeks.

This experiment simulates the decomposition of organic residues (worms, various soil animals) in the soil.

B. Ammonification of plant residues

Monitor the decomposition of green fertilizer in the soil by filling a 100 ml beaker with humus soil and burying several pieces of green stems and leaves of perennial lupine, peas, and beans planted in a pot in the fall. You can use dry parts of summer-harvested legumes steamed in water. Cover the glasses with a lid from a Petri dish, place in a thermostat at a temperature of 25-30°C for one to two weeks, maintaining normal soil moisture during the experiment (60% of the full moisture capacity), without overmoistening it.

Continuation of work No. 4 (carried out in 7-14 days)

a) Filter part of the culture solution from the test tubes in which the decomposition of animal proteins occurred. Pay attention to the formation of bad-smelling products (hydrogen sulfide - the smell of rotten eggs, indole compounds, etc.).

Detect the formation of ammonia by adding 2-3 drops of Nessler's reagent to 1 ml of culture solution. To do this, it is convenient to use a watch glass placed on a sheet of white paper or a porcelain cup. Yellowing of the solution indicates the presence of ammonia formed during the destruction of proteins.

Detect the presence of hydrogen sulfide by the blackening of the lead paper above the solution or when lowering it into the solution.

Drip the culture solution onto filter or chromatographic paper with a micropipette with a pulled-out spout (10-20 drops per point), dry it over a fan, drop in Salkovsky, Ehrlich or ninhydrin reagent. Heat over the stove. Indole compounds with Salkovsky's reagent give blue, red, crimson colors depending on the composition of the indole product (auxin indoleacetic acid gives a red color). Ehrlich's reagent gives a purple color with indole derivatives. Ninhydrin reagent is a reaction to the amino acid tryptophan (a precursor of indole auxins). When heated, it turns blue.

b) Remove a piece of meat or fish from the soil along with the soil adjacent to the piece, place it in a glass, pour in a little water, mash with a glass rod, shake, filter. Determine ammonia, hydrogen sulfide, and indole substances in the filtrate using the above methods. Similar processes occur in the soil when dead animals rot.

c) Remove half-decomposed stems of lupine green mass from the soil, clean them from the soil and grind them with a small amount of water. Filter 1-2 ml of the solution and make a test for ammonia nitrogen, released during the mineralization of plant proteins (with Nessler's reagent). Similar processes occur in the soil when plowing in green fertilizer or organic residues in the form of manure, peat, sapropel, etc.

Determine the presence of hydrogen sulfide, indole substances, tryptophan.

d) Place a drop of culture liquid from a test tube where the decomposition of animal protein occurred on a glass slide and examine it under a microscope at a magnification of 600. Numerous microorganisms are detected that cause the decomposition of organic substances. They often move vigorously and bend like a worm.

Introduction. 3

2 Safety requirements. 4

3 Experimental part. 4

Work No. 1. Determination of the formation of organic matter in plant leaves during photosynthesis (based on carbon content) 4

Work No. 2. Determination of the accumulation of organic matter in plant biomass and in soil. 8

Work No. 3. Determination of the consumption of organic matter by plants during respiration 11

Work No. 4. Decomposition of organic matter in water and soil with the determination of some end products. 14

One of the main assumptions of the heterotrophic hypothesis is that the emergence of life was preceded by the accumulation of organic molecules. Today we call organic molecules all those molecules that contain carbon and hydrogen. We also call molecules organic because it was originally believed that compounds of this kind could only be synthesized by living organisms.

However, back in 1828 Chemists learned to synthesize urea from inorganic substances. Urea is an organic compound that is excreted in the urine of many animals. Living organisms were considered the only source of urea until it could be synthesized in the laboratory. The laboratory conditions in which the organic compounds were obtained by chemists apparently, to some extent, imitate the environmental conditions on earth in the early period of its existence. These conditions could, according to the authors of the heterotrophic hypothesis, lead to the formation of organic compounds from oxygen, hydrogen, nitrogen and carbon atoms.

Nobel Prize winner Harold Urey, working at the University of Chicago, became interested in the evolution of chemical compounds on Earth in the early period of its existence. He discussed this problem with one of his students, Stanley Miller. In May 1953, Miller published an article entitled “The formation of amino acids under conditions similar to those that existed on Earth in the early period,” in which he indicated that A.I. Oparin was the first to express the idea that the basis of life, organic compounds, were formed during the period when the Earth’s atmosphere contained methane, ammonia, water and hydrogen, and not carbon dioxide, nitrogen, oxygen and water. Recently, this idea was confirmed in the robots of Urey and Bernal.

In order to test this hypothesis, in a specially created device, a mixture of gases CH4, NH3, H2O and H2 was passed through a system of pipes, and an electrical discharge was created at a certain point in time. The content of amino acids in the resulting mixture was determined.

An electric discharge was passed through an airtight device filled with methane, hydrogen and ammonia, designed by Miller. Water vapor came from a special device connected to the main part of the device. The steam, passing through the device, cooled and condensed in the form of rain. Thus, the laboratory quite accurately reproduced the conditions that existed in the atmosphere of the primitive Earth. These include heat, rain and brief flashes of light. A week later, Miller analyzed the gas that was under experimental conditions. He discovered that the previously colorless liquid had turned red.

Chemical analysis showed that some compounds appeared in the liquid that were not present at the beginning of the experiment. The atoms of some gas molecules recombined to form new and more complex organic molecules. By analyzing the compounds in the liquid, Miller discovered that organic molecules known as amino acids were formed there. Amino acids are made up of carbon, hydrogen, oxygen and nitrogen atoms.

Each carbon atom is capable of forming four chemical bonds with other atoms. Miller's experiments indicate that similar processes could have occurred in the Earth's atmosphere in the early period of its existence. These experiments provided important confirmation of the heterotrophic hypothesis.

Let’s not force ourselves into a strict framework from the very beginning and describe the term as simply as possible: the process of oxidation of organic substances (organics; these are, for example, proteins, fats and carbohydrates) is a reaction that results in an increase in the volume of oxygen (O2) and a decrease in the volume of hydrogen ( H2).

Organic substances are various chemical compounds that contain (C). The exceptions are carbonic acid (H2CO3), carbides (for example, carborundum SiC, cementite Fe3C), carbonates (for example, calcite CaCO3, magnesite MgCO3), carbon oxides, cyanides (such as KCN, AgCN). Organic substances interact with the most well-known oxidizing agent, oxygen O2, forming water H2O and carbon dioxide CO2.

The process of oxidation of organic substances

If we think logically, then since the process of complete oxidation is combustion, then the process of incomplete oxidation is the oxidation of organic matter, because with such an effect the substance does not ignite, but only heats it (accompanied by the release of a certain amount of energy in the form of ATP - adenosine triphosphate - and heat Q ).

The reaction of organic oxidation is not too complicated, so they begin to analyze it at the beginning of the chemistry course, and students quickly learn the information, if, of course, they make at least some effort. We have already learned what this process is, and now we have to delve into the very essence of the matter. So, how does the reaction proceed and what is it?

Oxidation of organic matter is a kind of transition, the transformation of one class of compounds into another. For example, the whole process begins with the oxidation of a saturated hydrocarbon and its transformation into an unsaturated one, then the resulting substance is oxidized to form alcohol; the alcohol, in turn, forms an aldehyde, and a carboxylic acid “flows” from the aldehyde. As a result of the entire procedure, we obtain carbon dioxide (when writing the equation, do not forget to put the corresponding arrow) and water.

This is an oxidation-reduction reaction, and in most cases the organic substance exhibits reducing properties, but itself is oxidized. Each element involved has its own classification - it is either a reducing agent or an oxidizing agent, and we give the name based on the result of the ORR.

The ability of organic substances to oxidize

Now we know that the process of redox reaction (redox reaction) involves an oxidizing agent, which takes electrons and has a negative charge, and a reducing agent, which donates electrons and has a positive charge. However, not every substance can enter into the process that we are considering. To make it easier to understand, let's look at the points.

Compounds do not oxidize:

• Alkanes – otherwise called paraffins or saturated hydrocarbons (for example, methane, which has the formula CH4);
• Arenas are aromatic organic compounds. Among them, benzene is not oxidized (in theory, this reaction can be carried out, but through several long steps; benzene cannot be oxidized independently);
• Tertiary alcohols are alcohols in which the hydroxyl group OH is bonded to a tertiary carbon atom;
• Phenol is another name for carbolic acid and is written in chemistry as the formula C6H5OH.

Examples of organic substances capable of oxidation:

• Alkenes;
• Alkynes (as a result we will trace the formation of an aldehyde, carboxylic acid or ketone);
• Alkadienes (either polyhydric alcohols or acids are formed);
• Cycloalkanes (in the presence of a catalyst, dicarboxylic acid is formed);
• Arenes (any substance that has a structure similar to benzene, that is, its homologues, can be oxidized to benzoic acid);
• Primary, secondary alcohols;
• Aldehydes (have the ability to oxidize carbons);
• Amines (during oxidation, one or more compounds with the nitro group NO2 are formed).

Oxidation of organic substances in the cells of plant, animal and human organisms

This is the most important question not only for those people who are interested in chemistry. Everyone should have this kind of knowledge in order to form a correct idea about various processes in nature, about the value of any substances in the world, and even about oneself - a person.

From school biology courses, you probably already know that the oxidation of organic matter plays an important biological role in the human body. As a result of redox reactions, the breakdown of BFA (proteins, fats, carbohydrates) occurs: heat, ATP and other energy carriers are released in the cells, and our body is always provided with a sufficient supply to perform actions and normal functioning of organ systems.

The occurrence of this process helps maintain a constant body temperature in the body not only of humans, but also of any other warm-blooded animal, and also helps regulate the constancy of the internal environment (this is called homeostasis), metabolism, ensures the high-quality functioning of cell organelles, organs, and also performs many more necessary functions.

During photosynthesis, plants absorb harmful carbon dioxide and produce oxygen necessary for respiration.

The biological oxidation of organic substances can occur exclusively with the use of various electron carriers and enzymes (without them, this process would take an incredibly long time).

The role of organic oxidation in industry

If we talk about the role of oxidation of organics in industry, then this phenomenon is used in synthesis, in the work of acetic acid bacteria (with incomplete organic oxidation, they form a number of new substances), and in some cases with organics it is also possible to produce explosive substances.

Principles of writing equations in organic chemistry

In chemistry, one cannot do without drawing up an equation - this is a kind of language of this science, which all scientists on the planet can speak, regardless of nationality, and understand each other.

However, the greatest difficulties arise when composing equations when studying organic chemistry.

Discussing this topic requires a very long period of time, so here we have selected only a short algorithm of actions for solving a chain of equations with some explanations:

1. Firstly, we immediately look at how many reactions occur in a given process and number them. We also determine the classes, names of the starting substances and substances that are ultimately formed;
2. Secondly, it is necessary to write out all the equations one by one and find out the type of their reactions (compound, decomposition, exchange, substitution) and conditions.
3. After this, you can create electronic balances, and don’t forget to set the coefficients.

Oxidation reactions of organic substances and their final products of formation

Benzene oxidation

Even under the most aggressive conditions, benzene is not susceptible to oxidation. However, benzene homologues are capable of oxidizing under the influence of a solution of potassium permanganate in a neutral environment to form potassium benzoate.

If you change the neutral environment to an acidic one, then benzene homologues can be oxidized with potassium permanganate or dichromate with the final formation of benzoic acid.

Formula for the formation of benzoic acid

Oxidation of alkenes

When alkenes are oxidized with inorganic oxidizing agents, the end products are so-called dihydric alcohols - glycogens. The reducing agents in these reactions are carbon atoms.

A clear example of this is the chemical reaction of a solution of potassium permanganate in connection with a weak alkaline environment.

Aggressive oxidation conditions lead to the destruction of the carbon chain at the double bond with the final products of formation in the form of two acids. Moreover, if the environment has a high alkaline content, two salts are formed. Also, acid and carbon dioxide can be formed as a result of the breakdown of the carbon chain, but in a strong alkaline environment, the products of the oxidative reaction are carbonate salts.

Alkenes are capable of oxidizing when immersed in the acidic environment of potassium dichromate according to a similar scheme given in the first two examples.

Alkyne oxidation

Unlike alkenes, alkynes are oxidized in a more aggressive environment. The destruction of the carbon chain occurs at the triple bond. A common property with alkenes is their reducing agents in the form of carbon atoms.

The output reaction products are carbon dioxide and acids. Potassium permanganate placed in an acidic environment will act as an oxidizing agent.

The oxidation products of acetylene, when immersed in a neutral medium with potassium permanganate, is potassium oxalate.

When a neutral environment is changed to an acidic one, the oxidation reaction proceeds to the formation of carbon dioxide or oxalic acid.

Aldehyde oxidation

Aldehydes are easily susceptible to oxidation due to their properties as strong reducing agents. As oxidizing agents for aldehydes, we can distinguish, as in the previous versions, potassium permanganate with potassium dichromate, as well as a solution of silver hydroxydiamine - OH and copper hydroxide - Cu(OH)2, which are predominantly characteristic of aldehydes. An important condition for the occurrence of the aldehyde oxidation reaction is the influence of temperature.

In the video you can see how the presence of aldehydes is determined in the reaction with copper hydroxide.

Aldehydes can be oxidized to carboxylic acids under the influence of silver hydroxydiamine in the form of a solution with the release of ammonium salts. This reaction is called the “silver mirror”.

The video below demonstrates an interesting reaction called the “silver mirror.” This experiment takes place in the interaction of glucose, which is also an aldehyde, with a solution of silver ammonia.

Oxidation of alcohols

The oxidation product of alcohols depends on the type of carbon atom to which the OH group of the alcohol is bonded. If the group is linked by a primary carbon atom, the oxidation product will be aldehydes. If the OH group of an alcohol is connected to a secondary carbon atom, then the oxidation product is ketones.

Aldehydes, in turn formed during the oxidation of alcohols, can then be oxidized to form acids. This is achieved by the oxidation of primary alcohols with potassium dichromate in an acidic environment during the boiling of the aldehyde, which in turn do not have time to oxidize during evaporation.

Under the condition of the excessive presence of oxidizing agents such as potassium permanganate (KMnO4) and potassium dichromate (K2Cr2O7), in almost any conditions, primary alcohols are capable of oxidizing with the release of carboxylic acids, into secondary alcohols, in turn, ketones, examples of reactions of which with the products of formation will be considered below.

Ethylene glycol or the so-called dihydric alcohol, depending on the environment, can be oxidized to form products such as oxalic acid or potassium oxalate. If ethylene glycol is in a solution of potassium permanganate with the addition of acid, oxalic acid is formed, if dihydric alcohol is in the same solution of potassium permanganate or potassium dichromate, but in a neutral environment, then potassium oxalate is formed. Let's consider these reactions.

We found out everything that needs to be understood at first and even began to analyze such a difficult topic as solving and composing equations. In conclusion, we can only say that balanced practice and frequent study will help you quickly consolidate the material you have covered and learn to solve problems.

I. Development of ideas about the origin of life on Earth.

1. Basic ideas explaining the origin of life on our planet:

• Life on earth was created by God.
• Living things on the planet have repeatedly spontaneously generated from non-living things.
• Life has always existed.

*Biogenesis – an empirical generalization (in the middle of the 19th century), asserting that everything

living things come only from living things.

• Life on earth was brought from outside (for example, from other planets).

*Hypothesis panspermia (proposed by G. Richter in 1865 and formulated by S. Arrhenius in 1895)

• Life arose at a certain period in the development of the Earth as a consequence of biochemical evolution. Theory abiogenesis (coacervate theory of A.I. Oparin).

2. The essence and significance of the works of Francesco Redi (1626-1698), Louis Pasteur (1822-1895).

II. Basic properties of living systems (criteria of living):

• complexity and high degree of organization
• unity of chemical composition
• discreteness
• metabolism (metabolism)
• self-regulation (autoregulation → homeostasis)
• irritability
• variability
• heredity
• self-reproduction (reproduction)
• development (ontogenesis and phylogeny)
• openness
• energy dependence
• rhythm
• adaptability
• a single principle of structural organization - the cell*

III. Modern ideas about the origin of life on Earth, based

on the theory of abiogenesis.

Conclusions:

1 – biological evolution was preceded by a long chemical evolution ( abiogenic );

2 - the emergence of life is a stage in the evolution of matter in the universe;

3 – the pattern of the main stages of the origin of life can be verified experimentally in the laboratory and expressed in the form of the following diagram:

atoms → simple molecules → macromolecules →

ultramolecular systems (probionts) → unicellular organisms;

4 – the primary atmosphere of the Earth had restorative character (CH 4, NH 3, H 2 O, H 2), due to this, the first organisms were heterotrophs ;

5 – Darwinian principles of natural selection and survival of the fittest

can be transferred to prebiological systems;

6 – currently living things come only from living things (biogenically). Opportunity

The re-emergence of life on Earth is excluded.

I. Inorganic evolution and conditions for the emergence of life on Earth.

1. The emergence of atoms of chemical elements is the initial stage of inorganic evolution.

In the depths of the Sun and stars, in the plasma, the formation of complex nuclei from the simplest occurs. Matter is in continuous movement and development.

Planet Earth was formed 4.5 - 7 billion years ago (gas and dust cloud).

The appearance of hard crust ( geological age) 4 – 4.5 billion years ago

Formation of the simplest inorganic compounds.

C, H, O, N, F (biogenic elements) are widespread in space and had a great opportunity to react with each other, which was facilitated by electromagnetic radiation and heat.

The Earth's primary atmosphere had restorative character: CH 4, NH 3, H 2 O, H 2.

Composition of the primary lithosphere: Al, Ca, Fe, Mg, Na, K, etc.

Primary hydrosphere: less than 0.1 volume of water in today's oceans, pH = 8-9.

Formation of the simplest organic compounds.

This stage is associated with the specific valency of carbon - the main carrier of organic life, its ability to combine with almost all elements, to form chains and cycles, with its catalytic activity and other properties.

Organic molecules are characterized mirror isomerism , i.e. they can exist in two structural forms, similar and at the same time different from each other. This feature of molecules existing in two mirror forms is called chirality. Among the organic substances that possess it are the molecular “building blocks” of life – amino acids and sugars. They are characterized by absolute chiral purity: proteins contain only “left-handed” amino acids, and nucleic acids contain only “right-handed” sugars. This is the most important feature that distinguishes living from non-living. Inanimate nature has a tendency to establish mirror symmetry (racemization) - a balance between left and right. Violation of mirror symmetry is a prerequisite for the emergence of life.

4. Abiogenic synthesis of biopolymers– proteins and nucleic acids.

Set of conditions : fairly high temperature of the planet’s surface, active volcanic activity, gaseous electrical discharges, ultraviolet radiation.

Adsorbed on the muddy bottom of drying sea lagoons, various monomers underwent polymerization, condensation, and dehydration under the influence of solar energy. The ocean was enriched with polymers, the formation of a “primary broth”, and the formation of coacervates.

Coacervates– clots of high-molecular compounds capable of adsorbing various substances. Chemical compounds can enter them osmotically from the environment and the synthesis of new compounds can take place. Coacervates act as open systems capable of metabolism and growth. Maybe mechanical crushing.

II. The transition from chemical evolution to biological.

A.I. Oparin (1894-1980) suggested that the transition from chemical evolution to biological is associated with the emergence of the simplest phase-separated organic systems - probionts , capable of using substances from the environment ( metabolism) and energy and implement on this basis the most important life functions are to grow and undergo natural selection.

The true beginning of biological evolution is marked by the emergence of probionts with code relationships between proteins and nucleic acids. The interaction of proteins and nucleic acids led to the emergence of such properties of living things as self-reproduction, preservation of hereditary information and its transmission to subsequent generations. Probably, at earlier stages of prelife, molecular systems of polypeptides and polynucleotides, independent of each other, existed. As a result of their combination, the ability to self-reproduction nucleic acids supplemented catalytic protein activity.