Subject: Squirrels. Qualitative determination of proteins in products .

Educational: organize the activities of students in the study and primary consolidation of knowledge about the chemical properties of protein.

Developing: To create meaningful and organizational conditions for the development of students:- the ability to conduct analysis, synthesis and, based on them, generalization and conclusions;- skills of safe work with laboratory equipment and reagents;
- ability to set goals and plan their activities;

Educational:

Promote students' awareness of the value of the subjects studied in their professional activities.
- Provide developmentability to work independently and together, listen to the opinion of classmates, prove their opinion;

Equipment and reagents: reagent boxes, solutions of sodium hydroxide, copper sulfate (II), concentrated nitric acid, chicken protein solution, test tube rack, alcohol lamps, matches, test tube holders, minced meat, bread, potato tubers, milk (homemade and store-bought), cottage cheese, sour cream, boiled peas, buckwheat, distilled water.

I. Organizational moment.

Trade cycle teacher : Hello guys! We also welcome our guests!

II. Message about the topic and purpose of the lesson. (slide number 1)

Knowledge update:

Chemistry teacher: On theprevious lessons in chemistry, we began to get acquainted with proteins and learned about their structure and functions in the body

Professional cycle teacher: And while studying professional modules, they learned how to cook dishes from products that include proteins.

Chemistry teacher: Tell guys, what else would you like to know about proteins as chemicals.

(Suggested answer: Learn the chemical properties of a protein)

What reactions can be used to determine the presence of protein in products)

Professional cycle teacher: Okay, but from the side of cooking technology?

(Suggested answer: What changes happen to proteins when cooking?-)

I II . Learning new material:

Chemistry teacher: We have set goals for ourselves, and now we will begin to implement them. So. Chemical properties of protein. I want to ask you, as experts in this field, to ask. What will happen to the protein (for example, chicken egg) if you heat it, fry it?(slide number 2)

(Suggested answer: color, density, smell, taste will change) Chemistry teacher: Moreover, the same changes occur with the protein if salts act on it. heavy metals, acids, alcohols.

This process is called protein denaturation.. (slide number 3)

Trade cycle teacher : And where does this property manifest itself in the technology of cooking:

(Suggested answer: - Souring milk is used in the manufacture of curdled milk.
- The clarification of broths is based on the coagulation of proteins during heat treatment
- cooking meat, fish, cooking cereals, vegetables, etc.)(slide number 4;)

Chemistry teacher: And now let's get acquainted with the qualitative reactions to the protein. What does quality response mean?

(Suggested answer: this is one with which you can recognize the substance)

Demo: slides

1. Xantoprotein reaction (for benzene rings contained in some amino acids). Under the action of concentrated HNO3, the proteins turn yellow.Slide #5

2. Biuret reaction (for the detection of the –CONH– group). If a little NaOH is added to a small amount of a protein solution and a CuSO4 solution is added dropwise, a red-violet color appears.(slide number 6)

Trade cycle teacher : And if we don’t conduct an experiment, where do we get information about the presence of protein in the product?

(Suggested answer: from the information on the label with the composition, it says ...)

Chemistry teacher: But now you yourself will try to determine the presence of protein and its relative amount in products - this will be done by a group of laboratory assistants. And a group of other experts will study the presence of the protein according to the information given by the manufacturer.

(performing work in pairs according to the options according to the instructive cards)

Group of expert laboratory technicians :

Instructional card: To add a little to a small amount of the issued productNaOH and add CuSO4 solution drop by drop.

Key: The appearance of a red-violet color indicates the presence of protein. The intensity of the color indicates the quantitative composition.

Option number 1: homemade and store milk

Option number 2: cottage cheese

Option number 3: Baton

Option number 4: Peas

Option number 5: Meat, bouillon cube Maggi

Option number 6: Buckwheat

Option number 7: Raw potatoes

Option number 8 Sour cream

2 Panels of theoretical experts :

Examine the composition of the issued products indicated by the manufacturer, confirm or refute the conclusions of the laboratory assistants.

№n, n

The product's name

Protein content in 100g of product, g

The discussion of the results. Conclusions:

Chemistry teacher: (referring to the professional cycle teacher) It turns out that the largest amount of protein is animal food. Maybe then give up vegetable protein altogether and eat meat instead of cereals?

Trade cycle teacher : No, that's where you're wrong! And what proteins are more beneficial for the body and how to cook them correctly will soon be told by the future chef, confectioner - ...... (student information) (presentation slide No. 7)

(Suggested answer: No. 1 Animal and vegetable proteins are absorbed by the body differently. If the proteins of milk, dairy products, eggs are digested by 96%, meat and fish - by 93-95%, then the proteins of bread - by 62-86%, vegetables - by 80%, potatoes and some legumes - by 70%. However, the mixture of these products is biologically more complete.The culinary processing of products is also important. On moderate heat food products, especially of plant origin, the digestibility of proteins increases slightly. With intensive heat treatment, digestibility decreases.Chemistry teacher: Thank you!

IV . Fixing:

1. Why, when poisoning people with salts of heavy metals: Hg, Ag, Cu, Pb, etc., egg white is used as an antidote?(Heavy metal ions that enter the body, in gastrointestinal tract bind to proteins into insoluble salts and are excreted without having time to harm (cause denaturation) the proteins that make up the human body).

2. Why is there a decrease in the mass of finished products during the heat treatment of meat and fish?
( Under the action of temperature, a change occurs in the secondary, tertiary and quaternary structures of the protein molecule (denaturation). Primary structure, and therefore chemical composition proteins do not change. During denaturation, proteins lose moisture (hydrogen bonds are broken), which leads to a decrease in the mass of the finished product.)

V . Reflection:

What have we been able to find out?

What was the most interesting today?

Who wants to praise someone?

VI . Dz. To solve the task : It is known that an adult needs 1.5 g of protein per 1 kg of body weight per day. Knowing your mass, determine daily allowance protein intake for your body.

Proteins are one of the most important and vital essential substances in the human body.

How often do we feel a deficiency of vitamins and minerals almost every year due to the piled-up melancholy and fatigue, and willingly, out of habit, we attribute it to “avitaminosis”. But it is important to understand that many health problems can be associated with a lack of quality protein. And this, unfortunately, we very rarely worry about.

How can we determine if our body has enough protein and is it time to replenish its reserves? Protein deficiency in the body can be seen by the following signs:

Cravings for sweets

This is one of the main signs of a lack of protein when you pounce on sweets and the feeling of hunger does not leave you. It just so happens that with the restriction of protein foods, we are in no hurry to lean on meat and eggs - the main task of proteins is to maintain blood sugar levels. And it is sweets that help to quickly correct the situation.

Poor concentration

The concentration will be excellent only with a balanced blood sugar level. And when this level is subject to constant fluctuations, then it may well be a feeling of foggy consciousness, in which it is impossible to concentrate on work or study. Therefore, remember: the brain must be constantly fed with proteins.

Hair loss
It is important to know that proteins are an indispensable building material for all cells, including hair follicles. When these follicles are strong, the hair will be held on the head, but with a chronic lack of proteins, they begin to actively fall out.

Weakness

It is well known that proteins are the main building material for muscles. Therefore, when there is a lack of protein in the body, the muscles begin to decrease in size. Over time, this condition can lead to chronic weakness and loss of strength.

Soreness
The whole system directly depends on the systematic influx of protein. the immune system human. That is why it is quite frequent colds and infectious diseases- a clear indication of a lack of proteins.

What contains protein

Animal and vegetable proteins

Most plant foods do not contain protein. less than in milk or chicken. But the human body is arranged in such a way that, as usual, protein is partially absorbed, everything else is excreted with urine. You should consume protein of both plant and animal origin - but this is ideal. If you're into any type of vegetarian diet, you'll just need to balance your diet to make up for the lack of animal protein.

animal protein

Which foods contain animal protein?

• kefir;
• hard cheeses;
• seafood and fish;
• cottage cheese;
• milk;
• egg white;
• dietary meat - rabbit and turkey;
• red meat;
• chicken.

All of these products contain both protein and fat, but not in the least amount. It should not be forgotten that among products containing protein, it is recommended to give preference to dairy products, the fat content of which is not more than 3%, skinless chicken and lean meat. As for cheeses, then fat content is allowed up to 40%.

Vegetable protein

Since vegetarianism is in fashion at the moment, we will tell you which plants contain a large amount of protein.

So nuts:

• Brazilian nut;
• macadamia nut;
• hazelnut;
• pine nuts;
• walnuts;
• almond oil and almonds.

Plant protein is digestible from cereals, however, you need to know, at least to combine with animal protein, in which cereals the protein is contained in large quantities:

• peanut;
• quinoa;
• oats;
• pearl barley;
• peas;
• lentils;
• buckwheat.

The most favorable combination is vegetable and animal protein at the same time on the same plate. And for this reason, we advise you to combine dairy products, fish and meat with vegetable protein, for example, with vegetables.

• Brussels sprouts;
• potato;
• beet;
• pumpkins;
• zucchini;
• zucchini;
• asparagus.

Seeds are also high in protein.

• linen;
• sesame;
• sesame;
• sunflower;
• pumpkin.

In fruits contains almost no protein, but there is something in any case. Accordingly, it will be useful to know in which fruits it is:

• coconut;
• figs;
• avocado.

Apr 30, 2016 tigress…s

In the experiments ahead of us, we will confine ourselves to simple qualitative reactions that will allow us to understand the characteristic properties of proteins.

One of the groups of proteins is albumins, which dissolve in water, but coagulate when the resulting solutions are heated for a long time. Albumins are found in the protein of a chicken egg, in blood plasma, in milk, in muscle proteins, and in general in all animal and plant tissues. As an aqueous solution of protein, it is best to take chicken egg protein for experiments.

You can also use bovine or porcine serum. Gently heat the protein solution to a boil, dissolve a few salt crystals in it and add a little dilute acetic acid. Flakes of coagulated protein fall out of the solution.

To a neutral or, better, to an acidified protein solution, add an equal volume of alcohol (denatured alcohol). At the same time, protein is also precipitated.

To the samples of the protein solution, add a little solution of copper sulfate, ferric chloride, lead nitrate, or a salt of another heavy metal. The resulting precipitation indicates that salts of heavy metals in large quantities are toxic to the body.

The problem of creating synthetic food not only for animals, but also for humans is one of the most important in modern organic chemistry. The most important thing is to learn how to get proteins, because agriculture provides us with carbohydrates, and it is possible to increase the supply of dietary fats at least by refusing to use them for technical purposes. In our country, in particular, Academician A.N. Nesmeyanov and his colleagues are working in this direction. They have already managed to obtain synthetic black caviar, which is cheaper than natural caviar and not inferior to it in quality.

Strong mineral acids, with the exception of orthophosphoric, precipitate the dissolved protein already at room temperature. This is the basis of the very sensitive Geller test, performed as follows. Pour nitric acid into the test tube and carefully add the protein solution along the wall of the test tube with a pipette so that both solutions do not mix. A white ring of precipitated protein appears at the boundary of the layers.

Another group of proteins is formed by globulins, which do not dissolve in water, but dissolve more easily in the presence of salts. They are especially abundant in muscles, in milk, and in many parts of plants. Plant globulins are also soluble in 70% alcohol.

In conclusion, we mention another group of proteins - scleroproteins, which dissolve only when treated with strong acids and undergo partial decomposition. They mainly consist of the supporting tissues of animal organisms, that is, they are the proteins of the cornea of ​​​​the eyes, bones, hair, wool, nails and horns.

Most proteins can be recognized using the following color reactions. The xantoprotein reaction consists in the fact that a sample containing protein, when heated with concentrated nitric acid, acquires a lemon-yellow color, which, after careful neutralization with a dilute alkali solution, turns orange. This reaction is based on the formation of aromatic nitro compounds from the amino acids tyrosine and tryptophan. True, other aromatic compounds can give a similar color.

When carrying out the biuret reaction, a dilute solution of potassium or sodium hydroxide (caustic potash or caustic soda) is added to the protein solution, and then a solution of copper sulfate is added dropwise. A reddish color appears at first, which turns into red-violet and then into blue-violet.

Like polysaccharides, proteins are broken down during prolonged boiling with acids, first to lower peptides, and then to amino acids. The latter give many dishes a characteristic taste. Therefore, the acid hydrolysis of proteins is used in the food industry for the manufacture of dressings for soups.

Grosse E., Weissmantel X.

Chemistry for the Curious. Fundamentals of chemistry and entertaining experiments.

Chapter 7 - continued

FATS - FUEL FOR THE BODY

We are already familiar with fats. They represent esters, formed by trihydric alcohol glycerin with saturated and unsaturated fatty acids, for example stearic, palmitic and oleic. We have already decomposed them with alkalis and thus obtained soap.
We also know that fats are the most important food. They contain much less oxygen than carbohydrates. Therefore, fats have a much higher heat of combustion.
However, it would be unwise, on this basis, to strive to provide your body only with fats that are rich in energy, but difficult to digest. At the same time, the body would wear out in the same way as an ordinary home stove, if instead of firewood it was heated with a much more high-calorie coal or even more anthracite.
By origin, fats are classified into vegetable and animals. They are do not dissolve in water and thanks to its low density float on its surface. But on the other hand, they are highly soluble in carbon tetrachloride ( carbon tetrachloride), trichloromethane ( chloroform), broadcast and other organic solvents.
Therefore, they can extract(extract) from crushed plant seeds or from animal products with the indicated solvents by heating.
We confine ourselves to finding fats in the kernels of nuts, poppy seeds, sunflowers or other plants. A small amount of the test sample must be ground, placed in a test tube, a few milliliters of carbon tetrachloride ( carbon tetrachloride) and heat for a few minutes.
(Carbon tetrachloride vapors are harmful to health and must not be inhaled! Conduct the experiment only in the open air or in a fume hood! Due to the risk of fire, never use flammable solvents such as ether or acetone!) Let's put a few drops of the resulting solution on a piece of filter paper and get a beautiful - so unpleasant on clothes, but necessary in our experience - fatty spot! If you heat the paper over the stove, the stain will remain - unlike stains essential oils, which volatilize under such conditions.
Another peculiar way of detecting fat is based on the fact that it spreads in a thin layer on the surface of the water. If very small particles of camphor are applied to the surface of water that does not contain fat, then they begin to spin - as if dancing. As soon as even the slightest trace of fat gets into the water, this dance immediately stops.
In addition, we can put a small amount of oil or a piece of fat into a test tube and heat it quickly on a strong flame of a Bunsen burner. This produces yellowish-white smoke.
If you carefully sniff the test tube, we will feel irritation in the nose, and tears in the eyes. This is due to the fact that during the decomposition of glycerol, an unsaturated alkanal (aldehyde) is formed. acrolein having the formula CH 2 \u003d CH-CH \u003d O. Its smell is all too familiar to many housewives who have burnt roasts. Acrolein is lacrimal and quite toxic.
In everyday life, many fats are often used - sometimes in excessive abundance - for cooking, frying, baking and making sandwiches. In the latter case, only solid or semi-solid ones are suitable, mainly animal fats such as butter and lard. Some vegetable fats, such as coconut, are too hard to spread on bread, and liquid oils for this, of course, are also not suitable.
We are indebted to the German chemist Normann for the fact that at present liquid fats can be turned into solid ones by processing them into margarine.
Liquid vegetable oils contain unsaturated fatty acid , mainly oleic (octadecene). The latter differs from saturated stearic (octadecanoic) acid, which is part of hard fats, only by the absence of two hydrogen atoms in the molecule. Oleic acid contains a double bond - between the ninth and tenth carbon atoms:
CH 3 -(CH 2) 7 -CH \u003d CH-(CH 2) 7 -COOH
In 1906, Normann managed to add hydrogen to oleic acid and thereby turn it into stearic acid. This hydrogenation reaction is accelerated in the presence of catalysts - finely divided platinum, palladium or nickel. Let's try to independently carry out the hydrogenation of a small amount of fat.

Fat curing - not so easy!

Curing 2 g of pure olive oil or sunflower oil.
We need a catalyst. Let's prepare it as follows. 0.5 to 1 g methanate ( formate) nickel, the preparation of which was described earlier, we will place in a test tube of refractory glass and will calcinate for 15 minutes in the high-temperature zone of the flame of a Bunsen burner.
This decomposes the salt and forms nickel metal in the form of a very fine powder.
Let the test tube cool down, and during this time it should not be moved in order to reduce the contact of nickel with air as much as possible. It is best to immediately close the test tube after calcination by inserting a piece of asbestos cardboard into it with tweezers.
After cooling, pour 5 ml of pure alcohol (denatured is not good) or ether. Then add a solution of 2 g of oil in 15 ml of pure alcohol.
Connect the test tube, which serves as a reactor, with device for producing hydrogen. The end of the outlet tube, through which hydrogen enters the test tube, must be pulled back so that the gas is released in the form of small bubbles.
Hydrogen leaving the device for gas evolution, before entering the test tube, must be very well purified so as not to poison the catalyst (In the laboratory, the purest hydrogen is obtained by electrolysis of water. However, hydrogen obtained by the interaction of aluminum with caustic solu- tion This method is preferable in this case to zinc and dilute (1M) sulfuric acid.
To do this, let's skip it through two more wash bottles. In the first, pour a solution of potassium permanganate, and in the second - a concentrated solution of caustic soda or caustic potash. Air must not enter the reactor. Therefore, hydrogen must first be passed only through the system where it is obtained and purified, and thereby force the air out of it. Only after that we will connect this system to the reactor and let hydrogen pass through the reaction mixture for at least an hour.
Gas must exit the reaction tube through the outlet tube. If he gives negative test on the explosive gas, it can be set on fire. And if it is not set on fire, then the experiment can only be carried out in a fume hood or in the open air, and, of course, there should be no sources of heat nearby, and even more so - open fire.
After the passage of gas is stopped, flakes fall out in the test tube, which, due to the presence of a catalyst, are colored in grey colour. Dissolve them in heated carbon tetrachloride and separate the catalyst filtering through a double layer of as thick filter paper as possible. When the solvent evaporates, a small amount of white "fat" remains.
This fat, of course, is not yet margarine. But it is it that serves as a raw material for the industrial production of margarine.
Hydrogenation of fats is carried out in the GDR at the plant in Rodleben and, in accordance with the plan, is being expanded from year to year. Valuable vegetable oils, such as peanut and sunflower, cottonseed and rapeseed oils, are cured. By mixing coconut and palm fat, the best varieties margarine - confectionery and cream. In addition, skimmed milk, egg yolk, lecithin and vitamins are added to fats in the manufacture of margarine.
Thus, we see that margarine is a valuable food product that is made from vegetable oils and other food additives as a result of their "ennoblement" by chemical treatment.

PROTEIN NOT ONLY IN EGGS

Life is a way of existence of complex protein bodies. Proteins are an important component of the protoplasm of all plant and animal cells. They are contained in the cell sap of plants, and in the muscles of animals, and in their nerve fibers, and in brain cells.
Proteins are the most complex chemical compounds. Their constituent parts have a simple structure. The German chemist Fischer, the founder of protein chemistry, as a result of many years of complex research, proved that proteins are built from amino acids.
The simplest amino acid glycine, or aminoethanoic (aminoacetic) acid. It corresponds to the formula NH 2 -CH 2 -COOH.
Characteristically, the glycine molecule includes the NH 2 group along with the COOH group inherent in carboxylic acids. Some amino acids also contain sulfur.
In amino acid molecules, there are not only simple carbon chains, but also aromatic rings, including those with heteroatoms. To date, about 30 amino acids have been isolated from proteins and studied. Of these, at least ten are indispensable for human nutrition. The body needs them to build its proteins and cannot synthesize them on its own.
Proteins of animal and especially plant origin usually do not contain all the amino acids necessary for life in sufficient quantities, therefore, human protein nutrition should be as varied as possible. It turns out that our tendency to eat a variety of foods is scientifically based.
All amino acids have the ability to form peptide bonds. In this case, the NH 2 group of one amino acid molecule reacts with the COOH group of another molecule. As a result, water is split off and products of complex composition are obtained, called peptides.
For example, if two glycine molecules are connected to each other in this way, then the simplest peptide arises - glycyl-glycine:

NH 2 -CH 2 -CO-NH-CH 2 - COOH

If not two, but a lot of molecules of different amino acids are combined, then more complex molecules are formed. proteins. These giant molecules, containing thousands or even millions of carbon atoms, are twisted into a ball or have a spiral-like structure.
AT last years remarkable progress has been made in protein synthesis. There were even production plans synthetic proteins on a large industrial scale as valuable animal feed (The problem of creating synthetic food not only for animals, but also for humans is one of the most important in modern organic chemistry. The most important thing is to learn how to get proteins, because agriculture provides us with carbohydrates, and increase the reserve of dietary fats can be at least due to the refusal to use them for technical purposes. In our country, Academician A. N. Nesmeyanov and his colleagues worked in this direction, in particular. They have already managed to obtain synthetic black caviar, cheaper than natural, and not inferior to it in quality. - Approx. transl.).
Every day science learns more and more about these important substances. Recently it was possible to unravel another mystery of nature - to reveal the secret of the "drawings" according to which the molecules of many proteins are built. Step by step, researchers are stubbornly moving forward, revealing the essence of those chemical processes that occur in the body with the decisive participation of proteins.
Of course, there is still a lot of work to be done to overcome the long road leading us to a complete understanding of these processes and the synthesis of the simplest forms of life.

In the experiments ahead of us, we will confine ourselves to simple qualitative reactions that will allow us to understand the characteristic properties of proteins.
One of the groups of proteins is albumins, which dissolve in water, but coagulate when the resulting solutions are heated for a long time. Albumins are found in the protein of a chicken egg, in blood plasma, in milk, in muscle proteins and in general in all animal and plant tissues. As an aqueous solution of protein, it is best to take chicken egg protein for experiments.
You can also use bovine or porcine serum. We carefully heat the protein solution to a boil, dissolve in it a few crystals of table salt and add a little dilute acetic acid. Flakes of coagulated protein fall out of the solution.
To a neutral or, better, to an acidified protein solution, add an equal volume of alcohol (denatured alcohol). At the same time, protein is also precipitated.
To the samples of the protein solution, add a little solution of copper sulfate, ferric chloride, lead nitrate, or a salt of another heavy metal. The resulting precipitation indicates that salts of heavy metals in large quantities poisonous for the body.
Strong mineral acids, with the exception of orthophosphoric, precipitate the dissolved protein already at room temperature. This is the basis of a very sensitive teller test, performed as follows. Pour nitric acid into the test tube and carefully add the protein solution along the wall of the test tube with a pipette so that both solutions do not mix. A white ring of precipitated protein appears at the boundary of the layers.
Another group of proteins is globulins, which do not dissolve in water, but dissolve more easily in the presence of salts. They are especially abundant in muscles, in milk, and in many parts of plants. Plant globulins are also soluble in 70% alcohol.
In conclusion, we mention another group of proteins - scleroproteins, which dissolve only when treated with strong acids and at the same time undergo partial decomposition. They mainly consist of the supporting tissues of animal organisms, that is, they are the proteins of the cornea of ​​​​the eyes, bones, hair, wool, nails and horns.

Most proteins can be recognized using the following color reactions.
xantoprotein reaction is that a sample containing protein, when heated with concentrated nitric acid, acquires a lemon-yellow color, which, after careful neutralization with a dilute alkali solution, turns orange (This reaction is found on the skin of the hands with careless handling of nitric acid. - Note transl. ).
This reaction is based on the formation of aromatic nitro compounds from amino acids. tyrosine and tryptophan. True, other aromatic compounds can give a similar color.

When conducting biuret reaction a dilute solution of potassium or sodium hydroxide (caustic potash or caustic soda) is added to the protein solution, and then a solution of copper sulfate is added dropwise. A reddish color appears at first, which turns into red-violet and then into blue-violet.
Like polysaccharides, proteins are cleaved during prolonged boiling with acids, first to lower peptides, and then to amino acids. The latter give many dishes a characteristic taste. Therefore, acid hydrolysis of proteins is used in the food industry for the manufacture of dressings for soups.

In a wide-mouthed 250 ml Erlenmeyer flask, place 50 g of dried and chopped pieces of beef or cottage cheese. Then pour concentrated hydrochloric acid there so that the entire protein is completely saturated (about 30 ml). We will heat the contents of the flask in a boiling water bath for exactly one hour. During this time, the protein will partially break down and a thick dark brown broth will form.
If necessary, after heating for half an hour, 15 ml of half diluted concentrated hydrochloric acid can be added. In total, it is advisable to take exactly as much acid as is needed for protein hydrolysis, because if there is too much of it, then after neutralization there will be a lot of salt in the broth.
In a second flask or in a clay pot, mix finely chopped or mashed vegetables and spices, for example 20 g celery, 15 g onions or leeks, a little nutmeg and black or red pepper, with 50 ml of 10% hydrochloric acid. We will prepare the latter by diluting 1 volume of concentrated acid with 2.5 volumes of water. We will also heat this mixture in a water bath until a brown color appears (usually this happens after about 20 minutes).
Then both mixtures are placed in a heat-resistant glass crystallizer or a large porcelain evaporating dish and mixed thoroughly. Pour 50 ml of water and neutralize the acid by gradually adding sodium bicarbonate (baking soda). This should be done gradually, in small portions, with a wooden or plastic spoon. The mixture must be thoroughly stirred all the time.
In this case, a lot of carbon dioxide will be released, and sodium chloride is formed from hydrochloric acid, or, more simply, table salt, which will remain in the broth. Thanks to salt, the broth is better preserved. The end of neutralization is easy to see by the cessation of foam formation when another small portion of baking soda is added. It must be added so much that the finished mixture shows a very slightly acidic reaction when tested with litmus paper.
Of course, the resulting concentrate can be used to make soup only if completely pure hydrochloric acid was taken for protein hydrolysis, i.e. pure for analysis or used for medical purposes (The latter can be purchased at a pharmacy. - Approx. Transl.) , because technical acid may contain impurities of toxic arsenic compounds (!).
The quality and taste of this soup may be different - depending on what products we have prepared it from. However, with absolutely exact observance of the above prescription, it is quite possible to eat it.
In industry, food concentrates of soups are introduced protein hydrolysates, obtained in a similar way from wheat bran (Often, other proteins are used for this, mainly of plant origin, from waste processing of oilseeds, as well as milk protein - casein. The obtained hydrolysates have a pleasant meat or mushroom taste. You can even get a hydrolyzate that is not inferior in taste to chicken broth. - Approx. transl.).
In recent years, one of the amino acids - glutamine, which is found in abundance in globulins. It is used in the free state or in the form sodium salt - monosodium glutamate. Let's add to our concentrate some pure monosodium glutamate or glutamic acid itself, the tablets of which can be bought at the pharmacy. This will give the concentrate a stronger taste. By itself, glutamic acid has only a mild taste, but it excites the taste buds and thus enhances the characteristic flavor of the food.

WHAT TURNS INTO WHAT?

Can you imagine what a giant chemical plant looks like? Huge pipes emit clouds of black, poisonous yellow or brown smoke into the air. Huge distillation columns, refrigeration units, gas holders and large industrial buildings give a peculiar outline to a chemical enterprise.
If we get to know the plant closer, we will be carried away by the intense rhythm of its continuous work. We will stop in front of huge boilers, walk along pipelines, hear the noise of compressors and the sharp, at first frightening sound with which steam escapes from safety valves.
However, there are also chemical plants that do not smoke or make noise, where there are no apparatuses and where day after day the old workshops are destroyed, giving way to new ones. Such chemical enterprises are living organisms.

METABOLISM

"Combustion" of food in the body is carried out in the cells. The oxygen required for this is provided by respiration and, in many living organisms, is carried by a special fluid - blood. In higher animals, blood consists of plasma and red and white blood cells suspended in it.
Red blood cells are erythrocytes, which give blood its color, consist of 79% of a complex protein. hemoglobin. This protein contains a red dye gem, attached to a colorless protein globin, from the group globulins.
The composition of hemoglobin in different animals varies greatly, but the structure of heme is always the same. From gema you can get another connection - hemin.
The anatomist Teichman was the first to isolate hemin crystals and thereby find a reliable method for identifying blood. This reaction makes it possible to detect the slightest traces of blood and is successfully used in forensic examination in the investigation of crimes. Put a drop of blood on a glass slide with a glass rod, smear it and dry it in air. Then we apply on this glass, a thin layer crushed to the smallest powder table salt, add 1-2 drops glacial acetic acid(in extreme cases, you can take high concentration acetic acid instead) and put a coverslip on top. We heat the glass slide with a weak (!) flame until the first bubbles form (glacial acetic acid boils at 118.1 ° C).
Then, with gentle heating, completely evaporate the acetic acid. After cooling, examine the sample under a microscope with a magnification of 300 times. We will see red-brown rhombic tablets ( prisms). If such crystals are not formed, then we again apply acetic acid to the border of contact of the glasses, let it seep inside and heat the glass slide again.
This reaction allows you to detect traces of dried blood on the tissue. To do this, we will treat such a spot with water containing carbon dioxide, for example mineral water, filter the extract, evaporate the filtrate on a glass slide and then process the sample in the same way as above.
For the first time, the German chemist Hans Fischer managed to synthesize and break down hemin in 1928. Comparing the formula of hemin (or heme) with the formula of the green pigment of chlorophyll plants indicates an amazing similarity of these compounds: The benzidine test also allows you to detect a small amount of blood. Let's prepare the reagent first. To do this, we dissolve 0.5 g of benzidine in 10 ml of concentrated acetic acid and dilute the solution with water to 100 ml. To 1 ml of the resulting solution, add 3 ml of a 3% solution peroxide(peroxides) hydrogen and immediately mix with a very dilute aqueous extract of blood. We will see a green coloration that quickly turns to blue.
In 5 liters of blood contained in the human body, there are 25 billion red blood cells, and they contain from 600 to 800 g of hemoglobin.
About 1.3 ml of oxygen can join 1 g of pure hemoglobin. However, not only oxygen can join hemoglobin. Its affinity for carbon monoxide (carbon monoxide) is 425 times greater than for oxygen.
The formation of a stronger bond of carbon monoxide with hemoglobin leads to the fact that the blood loses its ability to carry oxygen, and the poisoned person suffocates. That's why be careful with city gas and other gases containing carbon monoxide!
We now know that blood plays a vital role in metabolism. vehicle. Gas transfer, removal foreign substances, wound healing, transport of nutrients, metabolic products, enzymes and hormones are the main functions blood. All food that a person eats undergoes chemical processing in the stomach and intestines. These transformations are carried out under the action of special digestive juices - saliva, gastric juice, bile, pancreatic and intestinal juice.
The active principle of digestive juices are mainly biological catalysts- so called enzymes, or enzymes.
For example, enzymes pepsin, trypsin and erepsin, as well as rennet chymosin, acting on proteins, split them into the simplest fragments - amino acids from which the body can build its own proteins. Enzymes amylase, maltase, lactase, cellulase participate in the breakdown of carbohydrates, while bile and enzymes of the group lipase promote the digestion of fats. The influence of bile on the digestion of fats can be confirmed by the following experiment. Insert glass funnels into two identical flasks or Erlenmeyer flasks. In each of the funnels, lightly moisten a strip of filter paper with water.
Then, in one of the funnels, we soak the paper with bile (cow, pig or goose) and pour a few milliliters of food into both funnels. vegetable oil.
We will see that the oil only penetrates the strip of paper that has been treated with bile. The fact is that bile acids cause emulsification of fats, crushing them into tiny particles. Therefore, bile helps the body with enzymes that promote the digestion of fats. This is especially evident in the following experiment. If you can find the pork stomach, you need to turn it out, rinse with water and scrape off the mucous membrane with a blunt knife into a beaker. Pour four times the amount of 5% ethanol there and leave the glass for 2 days.
The resulting water-alcohol extract is filtered through a piece of cloth. Filtration can be greatly accelerated by suction on the suction filter with a water jet pump.
Instead of preparing such an extract, you can buy powdered pepsin at the pharmacy and dissolve it in 250 ml of water.
In conclusion, grate chicken egg white, hard-boiled (boil for 10 minutes), and mix it in a beaker with 100 ml of water, 0.5 ml of concentrated hydrochloric acid and a prepared extract containing pepsin, or with 50 ml of commercial pepsin solution.
Hydrochloric acid must be added because pepsin acts only in an acidic environment - at a pH of 1.4 to 2. The pH value of gastric juice due to the presence of hydrochloric acid in it is in the range from 0.9 to 1.5.
The glass will stand for several hours at a temperature of approximately 40 ° C in a warm place - at home near the stove or oven or in the laboratory in a drying cabinet. During the first quarter of each hour, the contents of the glass will be stirred with a glass rod.
After 2 hours, we will notice that the amount of protein has decreased significantly. After 6-8 hours, all the protein will dissolve and a small amount of white skin with a slight yellowish tinge will form. In this case, egg white, which has a complex structure, is hydrolyzed by water and turns into a mixture of compounds of a simpler structure - egg white. peptone. What a chemist can achieve only with concentrated acids, we have managed to achieve in our artificial stomach under exceptionally mild conditions.
The unpleasant sour smell of the contents of the glass is close to the smell of incompletely digested food. Now we will independently conduct a few more test-tube experiments related to the study of food digestion. Some of them deserve a brief explanation.
The breakdown of starch can be carried out in a test tube under the action of saliva on a liquid starch paste (37 ° C, 30 minutes -1 hour). The resulting sugar is detected using Fehling's reagent. The same result can be obtained by heating 10 ml of starch paste with 5 ml of bovine pancreas extract for 15 minutes in a water bath at 40°C. The extract is prepared by rubbing the pancreas with a small amount propanetriol(glycerin).
Such gruel from the pancreas is also useful for studying the digestion of fats. To this end, in a test tube half-filled with whole milk, add a 0.5% solution of soda (sodium carbonate) until a red color appears with phenolphthalein. If we now add gruel from the pancreas and heat it in a water bath to 40 ° C, then the red color will disappear again. In this case, free fatty acids are formed from the fat of natural milk.
Finally, using rennet (rennet) or a strip of purified calf gastric mucosa, we can isolate protein from raw milk casein. Chemists and biologists have discovered hundreds of interesting reactions that allow us to detect a wide variety of substances contained in the body. Let's take a look at some of these reactions. Cholesterol It is present in all organs, but most of all it is found in the brain, in bile and in the ovaries. This essential substance belongs to the group of polycyclic alcohols. sterols to which some sex hormones also belong. In addition, cholesterol is very similar in structure to ergosterol, an intermediate substance from which vitamin D is obtained.
Cholesterol was originally found in gallstones and is therefore called "hard bile". were later opened sterols vegetable origin. Previously, cholesterol was found only in vertebrates, including humans. Therefore, his presence was considered a sign of a high level of development of living beings. However, scientists from the GDR were the first to detect cholesterol in bacteria.
Extract cholesterol from egg yolk with diethyl ether.
Then mix 0.5 ml of glacial acetic acid and 2 ml of concentrated sulfuric acid, heat for 1 minute and finally cool thoroughly. In a test tube, under the layer of egg yolk extract, carefully introduce the cooled mixture of acids - so that the contents do not mix. Let's leave the tube for a while. After some time, several zones with different colors are formed in it.
Above the layer of colorless acid, we will see a red layer, and above it, a blue layer. Even higher is a yellowish hood, and above it is a green layer. This beautiful play of colors will probably please readers. The reaction carried out is called the Lieberman reaction.
(Often, cholesterol is determined using the beautiful Lieberman-Burchard color reaction. To a solution of 5 mg of cholesterol in 2 ml of chloroform, add 1 ml of acetic anhydride and 1 drop of concentrated sulfuric acid. When shaken, a pink color is formed, quickly changing to red, then blue, and finally green. - Approx. transl.).
Cholesterol can also be detected using another color reaction - according to the Salkovsky method. In this case, several milliliters of the extract are mixed with an equal volume of dilute (approximately 10%) sulfuric acid. acid layer fluoresces in green, and the extract acquires a color from yellow to intense red.
(Both reactions - Lieberman and Salkovsky - may not work the first time if the ratios of the reagents are unsuccessfully chosen. The Salkovsky test is easier to obtain. If, for example, the extract is obtained by diluting 6 ml of the yolk to 50 ml with ether, then it is best to add to 1 ml of such an extract 2 ml of 10% sulfuric acid.
A beautiful color reaction is also obtained when a bile pigment is found in the urine. To do this, nitric acid is carefully added dropwise to the wall in a test tube half-filled with urine. As a result, a green zone is formed in the lower part of the test tube, which turns into blue, purple and red.
The presence of bile pigment in the urine indicates a person's disease. In general, when recognizing certain diseases, reliable conclusions can be obtained through the analysis of urine and feces - the end products of metabolism in a living organism. These are slags that the body does not need and therefore must be turned off from the metabolism. However, we know that these substances do not waste uselessly, but are included as a necessary link in the cycle of substances in nature.