: buy cheap in Rostov-on-Don.

75 comments to “How to Test Protein for Authenticity and Protein Content”

Perhaps this article will be useful for athletes. Of course, I lead a healthy lifestyle. But I don't use extra protein.

What's on the spoon?

• Burnt original 80% KSB in a spoon
  ("Textrion Progel 800" to be exact).

Hello dear site owner! I really liked your site. You have a lot of useful and interesting information.

The main thing is the result from the use.
In most cases, they buy protein for mass gain.
There may be a content of 90% (soy isolate) - but nothing will be absorbed.

Buying from the USA - the probability of a fake is minimal. But there are problems with delivery.

And buying by weight is buying a cat in a “poke”, they can send anything. Somewhere here it was indicated - Shchuchinsky KSB for 70 UAH - I was offered to buy, but after reading, I found out that this was an overdue batch (shelf life there is 6 months in total). This one needs to be thrown away. Although all tests show everything is OK

• The result may not be the fault of the protein.

  Soy isolate is not 100% digestible. But to say that “nothing will be assimilated” is not correct. Soy protein is digested by 80-60%. (See the article "Biological value of protein"). If the percentage of assimilation is correlated with the price, then soy protein is a very good source of protein (ideally interfere: 70-80% CSB + 30-20% soy isolate).

  By weight it is worth buying only from trusted sellers.

Dmitry, can you somehow check what kind of protein is there? That is, for example, find out soy or whey. Just falsification can be replaced by more cheap protein concentrate(which is soy).

• Visually and by any other physical properties, it is impossible to reliably distinguish whey protein from soy protein.

  But, if there is a personal experience of using different protein concentrates, then it is easy to distinguish whey from soy (just like from casein, albumin, etc.). Because These protein concentrates are very different in taste and solubility.

  If there is no personal experience, then there are two options:
  - or ask someone who has personal experience to try,
  Or buy from a trusted seller.

  Ps: In laboratory conditions (sanitary stations, for example), only the nutrient composition is determined: the amount of proteins, carbohydrates.

And who will tell contacts of the official distributor "DMV" Ukraine or maybe his website, otherwise I can’t find something in any way ...

• During souring of milk - when bacterial enzymes convert milk sugar (lactose) into lactic acid (lactate) - under the action of lactic acid, calcium caseinate (or rather, caseinate-calcium phosphate complex) coagulates (curdles), turning into free protein casein. At the same time, calcium6, detached from calcium caseinate, attaches lactic acid, forming calcium lactate, and precipitates. As a result, the digestibility of casein increases significantly. Therefore, curdled milk, kefir and cottage cheese have an advantage over milk in terms of the efficiency of casein absorption. It should be noted that casein in a bound state (calcium caseinate) is highly soluble in water. Pure casein is insoluble. The latter quality of casein is well known to athletes who use casein blends. The latter, like whey protein, are produced in the form of a powder for rational (including sports) and therapeutic nutrition.

  What do you think about this, maybe this sediment is pure casein, and the sediment is the so-called calcium lactate?

  Dmitry, thank you for the quick response.

  • The fact is, Stanislav, that casein is obtained (isolated from milk) by precipitation (during precipitation, the protein denatures). Therefore, it is not possible to reprecipitate the protein (because the protein can only be denatured once). My opinion: casein protein concentrate should not precipitate (I could be wrong).

Signature: “How to check the presence of protein incorrectly” - highlight - for especially stupid and not attentive.

• Written in capital letters and highlighted in bold. Thanks for the note, Michael.

How to test a gainer? Do all mixtures have to be white or close to white?

• Eugene, check the gainer for the presence of what (what nutrient) are you interested in?

  If for protein, then only qualitatively (either there is protein or not; its amount cannot be determined at home).
  - If carbohydrates - so they should be in the gainer.

  The color of the gainer depends on the dyes. The color of proteins and carbohydrates is white (or beige).

  As for me, the only thing that should be of interest to the consumer of a gainer is whether the amount (%) of proteins corresponds to what is stated on the package and the quality of carbohydrates (their glycemic index). But it is possible to determine the amount of protein only in laboratory conditions (and even then, not in all).

Bought a gainer. And after opening the package, I realized that it was fake. I'll explain why.
- Firstly, the consistency, a very light cocoa-colored powder, in fact, it smells like cocoa, although the taste is chocolate.
- Secondly, it does not curl up, but dissolves like cocoa in boiling water.
- Thirdly, when mixed with milk, “chocolate milk” is obtained without any dense mass.
- Fourthly, a gainer or protein should crunch like snow, and it just “crumbles” like flour or cocoa.
After that, I carefully studied the packaging and did not find any information in Russian. Although this product should be with a Russian label, according to Rospotrebnadzor.
And finally, it seems to me that any sane a person who has had previous experience with sports nutrition distinguishes a real product from a fake .
It's a shame that a considerable amount has been spent, which cannot be returned without a trial, and what was left without quality product, which was going to be used for its intended purpose, and not "dye the water."

• Eugene, the main criterion in determining the authenticity of a gainer is your own experience (the rest of the analysis is secondary when analyzing a multi-component product).

  The absence of a label in the native language is not yet an indicator of a fake. It is rather an indicator of the smuggling of the product. So, for example, some KSB, which are imported into Ukraine (and, moreover, in a considerable amount), do not have domestic certification. At the same time, these German KSBs are enough High Quality(there is no doubt in the regulatory norms of the European Union).

I didn't believe my own experience at first. He dumped everything on "it seemed". And then I decided to make sure with various artisanal samples, and then it already became clear that they were bred.

What is on many forums the topic of fakes has become very popular, visible to the naked eye. I understand that many forums are also created for PR of some particular product or for not validating negative reviews about fakes, for example. But I was in no way ready that a store that seemed to be popular on the network, with a large assortment and a considerable audience, would be selling counterfeit products, and so obviously. Therefore, everyone who starts exercising in gyms, I urge you to be careful, because one thing is the loss of money, and another thing is the loss of health, and, God forbid, life. Nobody is immune from this.

I buy everything only in trusted sports nutrition stores. In Vkontakte groups, it is hardly possible to purchase a worthwhile gainer or protein at all. And stores with a long history will not spoil their reputation and sell only high-quality protein.

• ✸ "Verified Stores" is right. But verification takes time. And for a beginner who decides to buy sports nutrition for the first time in his life (and has not encountered falsification), there are no trusted stores. Often for such buyers the main criterion is "cheaper". Besides, in social networks many feel very comfortable and safe :).

  ✸ Vkontakte you can buy the original sports nutrition, but I, like you, prefer the online store (“checked” personally). Vkontakte bought falsified protein - he became more experienced and smarter. Once is enough, the second time for the same rake ... no

Hello. I bought whey isolate from Syntrax nectar. There is not a word in Russian on the package, the label is pasted a little unevenly, it smells like dry milk. Tell me how to check the isolate? Looking forward to your reply, thanks in advance.

• The fact that the information on the packaging is not written in Russian does not mean falsification. Almost all sports nutrition in Russia, Ukraine and Belarus is not legalized (does not have domestic certificates of conformity).
  But a crookedly glued label is very alarming - a self-respecting company with a name will not allow this.
  If the protein is unflavored, then it should have a milky smell.
  It is very easy to check the product for the presence of protein - dissolve 1 tablespoon in 100 ml of water and boil for 2 minutes.

  • Thanks for the answer, I checked, the protein turned out to be genuine.

    Hello Dmitry, tell me please, I bought “bsn syntha 6 isolate” and so, when I boil it, it doesn’t curdle, I have never taken isolate before and I don’t know if I took it genuine or not !?

    • • Thanks for the answer.

• Please note, Vladislav, that Optimum Nutrition produces a product with the name “ 100% Whey Gold Standard”, and not “100% Gold standard Whey protein” (look at the official website) [Although variations in the sound of the name are possible in everyday life].
  

  In addition, it is not profitable to sell branded sports nutrition by weight: even if “Gold Standard 100% Whey” is bought in 4.5 kg bags, and sold by weight in 1 kg, then all the same “the skin is not worth it”.

  Do you need to “distinguish casein protein from whey protein” if the falsification is obvious? (Both the name of the product, and "weight", and not sticking to the teeth and boiling confirmed this).

  Ps: When checking a branded sports nutrition for authenticity, the color of the water after dissolving and boiling the powder does not play a role.

Tell me, please, just to be sure: if you cook the protein while stirring, the protein will remain in any case, it cannot dissolve in any way?

• If you cook for several hours, then the protein will gradually dissolve (the protein is hydrolyzed to peptides) - and you get a broth. If you boil the protein solution for 10 minutes, the protein cannot dissolve (protein clumps will float).

Hello. I recently purchased a whey protein concentrate, or rather, they adjusted it to me “brotherly”; so I can't tell you what manufacturer it is from. When you try to stir the protein - it, the protein, begins to curl up strongly, a kind of balls form on the surface of the milk. Tell me, is it supposed to be like this?

• How the protein concentrate behaves when boiled depends on the type of the latter.
  - If it is KSB, then when boiled, the whey protein coagulates: ~ it looks like clots - like boiled rice, only the particles are a little larger.
  - If we are dealing with a complex protein (whey + casein), or micellar casein, or soy isolate, then this picture will not be observed. "Soya" turns into a kind of jelly.
  - Calcium caseinate also forms clots (larger than whey).

  Never any protein spontaneously [without exposure high temperature] does not collapse.
  If you stir the protein in cold milk, then small balls of milk fat form on the surface of the drink and along the walls of the shaker.

Thank you for your reply. He incorrectly expressed his thoughts by saying “it starts to curl up strongly”, you just had to write that white balls are formed.

Dmitry, good afternoon! I want to express my deep gratitude for your invaluable useful work on this site. Please help me to understand the authenticity of the purchased product and me.
My situation is the following. I bought the KSB for the first time through the VKontakte page. There is also no photo of the seller, as you described in other articles about scammers. Picked up by self-delivery from Ivanteevka in the Moscow region. Three of us came (the seller knew that the three of us would come, but he was not afraid to go out) paid 650 rubles per 1 kg. Seeing in the process of communication that we are inexperienced in this matter, the seller, being very friendly, told us a lot useful information about creatine and L-carnitine of interest to us. He offered to take it for free for testing (in principle, this was also offered on his page). The seller was open to communication, did not seem "muddy".
Yesterday, after reading your articles here, I conducted all the described experiments to test the protein, except for burning on a spoon) Result: in the mouth, the powder folds into lumps, when boiled, the same positive reaction, which is described by you, the creak of "snow" is also present, in an iodine solution it does not change color, but becomes slightly cloudy, there is practically no smell, it tastes very much like typical dry milk. Dmitry, what else can be a catch, if there is one, because the sale is not from the official site, and, as far as I understand, not officially at all? How can you determine if an expired product is being sold? Thank you.

• Vadim, why are you winding yourself up and trying to find a "trick" if the product is of high quality and beyond doubt.
  If everything was sold from "official sites", then 1) the variety of goods would be minimal, and 2) prices would be several times higher.
  Don't worry about the expiration date either. In KSB it is usually 18 months. And even if the product is overdue for several months, this will not affect its properties in any way, because. the moisture and fat content in the powder is negligible (approx. 5%), which means that oxidation processes are minimal.

  • Thanks;)

Most importantly: are there really factories abroad that sell protein in bags to everyone?

• If the buyer is from the same country as the factory, then [theoretically] anyone can buy the factory's products.
  = If the buyer is a foreign citizen, then in order to introduce the product into your home country, you must have a permit to conduct foreign economic activity (this applies to cases when the goods are purchased not for personal use, but for commercial purposes).
  = If there is an official representation of the factory in the native country, then the factory will send a foreign citizen straight to the local representative.

Well, why can't dairy plants produce protein in our country?

• In Ukraine, there are milk processing plants producing CSB and calcium caseinate (in Lviv and Kherson regions, for example).

Nevertheless, their products are not in demand in their country.

Well, why not establish an excellent production of such a product? We have a lot of milk, we have factories ... What's stopping you?

I don’t know how expensive the equipment is, but I’m sure that there is definitely an opportunity to install it at least at one plant!
But I am convinced that no one thinks about people, and they make money on shit, for which they fight a lot ...

• If high-quality protein concentrates could not be bought at all, then one could be upset about this. But high-quality KSB [from Europe] is available in Ukraine (although in most cases illegally) and you can buy it.

Well, of course you can buy anything today! But why overpay for expenses, say, from Holland, if you could buy your own at your side. Especially the one who is engaged, because for him it is necessary as water and in considerable portions. And with the prices of protein, even the one by weight, you don’t really get enough. Do not forget that you still need to pay for the hall and all the associated costs associated with it. And to build a couple of kg of muscle turns into a rather big sum ...

• Bodybuilding is one of the most expensive sports.
  For example, I have for February:
  — 300 UAH — KSB
  – 30 UAH – maltodextrin
  – 50 UAH – BCAA
  — 30 ​​UAH — vitamins
  — 120 UAH — subscription to the hall
  + some UAH creatine
  Total: 530 UAH (and this is taking into account the fact that I get sports nutrition at low prices).

  • Dmitry, I wanted to ask you, where do you buy sports nutrition, I would like to know a trusted supplier of high-quality sports nutrition, so as not to think later what if I bought a fake, and buying where you are I would be calm)))))

• And why Buchatsky KSB turned out to have less protein. Here, after looking at their website, there are 3 options for it: 35%, 60% and 70%. If they sell 70%, and 60 or 35 are poured there, then it is natural that it is less.

  • As the person who handed over Buchatsky KSB-70 to the laboratory told me, the protein content in the powder was less than 50% (I do not guarantee that the information is 100% reliable - it was a long time ago and I remember accordingly).
    In addition, not only % protein is important in the WPC. When a product is consumed several times a day, its other properties are very important, such as: solubility, taste, digestibility.

I decided to resume the use of whey after a + -8 month break. The old prot remained, but after tasting it, I felt a change in taste, does this mean that it is time for it to go to the trash can? sorry for stupid question)

• If the protein was not stored in conditions of high humidity and direct sunlight did not fall on it, then it can be safely consumed blindly (despite the fact that its taste has changed slightly).

Dmitry, hello.
Tell me: how long and at what temperature can I store a bag of Lactomine 80 opened in a promotional package (20 kg)?

And one more thing ... Friends bought "Laktomin 80" - 20 kg., The packaging was original, as on the manufacturer's website, but inside it was simply poured into a multilayer paper bag, there was no polyethylene liner (bag).

• If stored under conditions that exclude exposure to direct sun rays and high humidity, then within 2 years the KSB should not deteriorate.
  If a bag without a polyethylene liner was purchased in the Russian Federation, then this is quite possible, because. Lactomine is imported into the Russian Federation not in bags and is packaged in bags “on the spot”.
  If such a bag was purchased in Ukraine, then there is a high probability of counterfeit.

Dmitry, please tell me how to test beef protein for authenticity?

• You can check the AUTHENTICity of beef protein in the same way as any other product: evaluate the packaging, label ...
  = But, it is possible to test for the PRESENCE of PROTEIN and, moreover, its quantitative content only in laboratory conditions. The only necessary information that can be obtained at home is the formation of broth during prolonged boiling [powder dissolved in water].

Dmitry, please tell me, we want to set up the release of good sports nutrition, but the question arose on a protein shake with cocoa, I can’t choose the type of cocoa that will dissolve in cold milk without sediment. I have already tried species from our Russian to German species, but to no avail. In combination with serum, there is no sediment, but with nat. the protein is precipitated, there is no desire to add chemistry, maybe you can tell the type of cocoa ?.

• Julia, I won’t advise you anything about cocoa powder, because. incompetent in this matter. I think that manufacturers of sports nutrition do not work with cocoa as a flavoring additive. As an option, you can master the production of micronized cocoa powder yourself. Well, add lecithin as a [natural] emulsifier.

  I don’t understand the phrase “there is no sediment with serum, but with nat. protein is precipitated. What then do you consider proteins to be natural, and which are not?

  Ps: You can check out kakao powder on amazon.

Tell me, what does the smell of plastic in whey protein indicate?

• I don't have an answer to your question. I can only say that I encountered a similar problem: several people made similar complaints about Meggle's milk protein concentrate - "MTM Sport 5".

My weight is 60 kg. Can I take protein powder? If possible, which one?

• Anton, weight is not the main reason for the use or non-use of protein. The need for protein supplements is dictated by the need for protein - if your protein needs (you have to calculate them) are not covered by regular foods, you should look at protein supplements.
  On the issue of protein selection, I will not particularly explain. Buy whey protein.

Bought protein by weight.
If you take it with your fingers, there is a sound like snow; in the mouth it also sticks to the palate and teeth. But when boiling, no clots appeared. And absolutely. Maybe I did it wrong, but it foamed a lot and ran out of the bowl (stirring did not help), so I had to remove it from the stove and then put it back. The powder is slightly sweet and white color, but after boiling it acquired the color of melted chocolate ice cream, maybe a little lighter. Despite the sound of snow and sticking there is no squirrel coming out?

• Arthur, you didn't say what kind of protein you bought: whey, soy, egg, casein. Because those signs that you expected to get, they are characteristic only (!) For whey protein. But, "melted ice cream" after boiling - it looks like soy isolate.

He diluted the cocktail, but he could not drink it completely. left in the fridge. in the morning in the shaker ((and it is transparent) a significant sedimentary layer was found. Is the product not real?
and another question - can you drink it after a day in the refrigerator ???

• The presence of sediment does not indicate falsification. Natural substances may precipitate. Branded protein should not precipitate due to the presence of an emulsifier. (…in theory).
  A pre-made protein shake can keep overnight in the refrigerator (although, for the future, it's best to dissolve the protein in less liquid and sip it fresh).
  The gainer, when standing for a long time, definitely gave a precipitate (I remember this). KSB does not precipitate (as far as I remember), and I haven’t used branded protein for a long time.

Hello. I bought a prot vader goldway 3 kg. Cardboard box inside a plastic bag with prot, also in the box is a measuring spoon. The box has a paper with a barcode on it. The barcode program issues a link to another vader product. But it determines what was released in Germany. It seems that all the inscriptions on the package coincide with those on other packages. There is no inscription on the package where it was produced

No. 1. Proteins: peptide bond, their detection.

Proteins are macromolecules of linear polyamides formed by a-amino acids as a result of a polycondensation reaction in biological objects.

Squirrels are macromolecular compounds built from amino acids. 20 amino acids are involved in making proteins. They link together into long chains that form the backbone of a large molecular weight protein molecule.

Functions of proteins in the body

The combination of peculiar chemical and physical properties of proteins provides this particular class of organic compounds with a central role in the phenomena of life.

Proteins have the following biological properties, or perform the following main functions in living organisms:

1. Catalytic function of proteins. All biological catalysts - enzymes are proteins. To date, thousands of enzymes have been characterized, many of them isolated in crystalline form. Almost all enzymes are powerful catalysts, increasing the rates of reactions by at least a million times. This function of proteins is unique, not characteristic of other polymeric molecules.

2. Nutritional (reserve function of proteins). These are, first of all, proteins intended for nutrition of the developing embryo: milk casein, egg ovalbumin, storage proteins of plant seeds. A number of other proteins are undoubtedly used in the body as a source of amino acids, which, in turn, are precursors of biologically active substances that regulate the metabolic process.

3. Transport function of proteins. Many small molecules and ions are transported by specific proteins. For example, respiratory function blood, namely the transfer of oxygen, is carried out by molecules of hemoglobin - a protein of erythrocytes. Serum albumins are involved in lipid transport. A number of other whey proteins form complexes with fats, copper, iron, thyroxine, vitamin A and other compounds, ensuring their delivery to the appropriate organs.

4. Protective function of proteins. The main function of protection is performed by the immunological system, which provides the synthesis of specific protective proteins - antibodies - in response to the entry of bacteria, toxins or viruses (antigens) into the body. Antibodies bind antigens, interacting with them, and thereby neutralize their biological effect and maintain the normal state of the body. The coagulation of a blood plasma protein - fibrinogen - and the formation of a blood clot that protects against blood loss during injuries is another example of the protective function of proteins.

5. Contractile function of proteins. Many proteins are involved in the act of muscle contraction and relaxation. The main role in these processes is played by actin and myosin - specific proteins of muscle tissue. The contractile function is also inherent in the proteins of subcellular structures, which provides the finest processes of cell vital activity,

6. Structural function of proteins. Proteins with this function rank first among other proteins in the human body. Structural proteins such as collagen are widely distributed in connective tissue; keratin in hair, nails, skin; elastin - in the vascular walls, etc.

7. Hormonal (regulatory) function of proteins. Metabolism in the body is regulated by various mechanisms. In this regulation, an important place is occupied by hormones produced by endocrine glands. A number of hormones are represented by proteins or polypeptides, for example, hormones of the pituitary gland, pancreas, etc.

Peptide bond

Formally, the formation of a protein macromolecule can be represented as a polycondensation reaction of α-amino acids.

From a chemical point of view, proteins are high-molecular nitrogen-containing organic compounds (polyamides), whose molecules are built from amino acid residues. Protein monomers are α-amino acids, common feature which is the presence of a carboxyl group -COOH and an amino group -NH 2 at the second carbon atom (α-carbon atom):

Based on the results of studying the products of protein hydrolysis and put forward by A.Ya. Danilevsky's ideas about the role of peptide bonds -CO-NH- in the construction of a protein molecule, the German scientist E. Fischer proposed at the beginning of the 20th century the peptide theory of the structure of proteins. According to this theory, proteins are linear polymers of α-amino acids linked by a peptide bond - polypeptides:

In each peptide, one terminal amino acid residue has a free α-amino group (N-terminus) and the other has a free α-carboxyl group (C-terminus). The structure of peptides is usually depicted starting from the N-terminal amino acid. In this case, amino acid residues are indicated by symbols. For example: Ala-Tyr-Leu-Ser-Tyr- - Cys. This entry denotes a peptide in which the N-terminal α-amino acid is ­ lyatsya alanine, and the C-terminal - cysteine. When reading such a record, the endings of the names of all acids, except for the last ones, change to - "yl": alanyl-tyrosyl-leucyl-seryl-tyrosyl--cysteine. The length of the peptide chain in peptides and proteins found in the body ranges from two to hundreds and thousands of amino acid residues.

No. 2. Classification of simple proteins.

To simple (proteins) include proteins that, when hydrolyzed, give only amino acids.

Proteinoids ____simple proteins of animal origin, insoluble in water, salt solutions, dilute acids and alkalis. They perform mainly supporting functions (for example, collagen, keratin

protamines - positively charged nuclear proteins, with a molecular weight of 10-12 kDa. Approximately 80% are composed of alkaline amino acids, which makes it possible for them to interact with nucleic acids through ionic bonds. They take part in the regulation of gene activity. Well soluble in water;

histones - nuclear proteins that play an important role in the regulation of gene activity. They are found in all eukaryotic cells, and are divided into 5 classes, differing in molecular weight and amino acid. The molecular weight of histones is in the range from 11 to 22 kDa, and the differences in amino acid composition relate to lysine and arginine, the content of which varies from 11 to 29% and from 2 to 14%, respectively;

prolamins - insoluble in water, but soluble in 70% alcohol, chemical structure features - a lot of proline, glutamic acid, no lysine ,

glutelins - soluble in alkaline solutions ,

globulins - proteins that are insoluble in water and in a semi-saturated solution of ammonium sulphate, but soluble in aqueous solutions of salts, alkalis and acids. Molecular weight - 90-100 kDa;

albumins - proteins of animal and plant tissues, soluble in water and saline solutions. The molecular weight is 69 kDa;

scleroproteins - proteins of the supporting tissues of animals

Examples of simple proteins are silk fibroin, egg serum albumin, pepsin, etc.

No. 3. Methods for isolation and precipitation (purification) of proteins.

No. 4. Proteins as polyelectrolytes. Isoelectric point of a protein.

Proteins are amphoteric polyelectrolytes, i.e. exhibit both acidic and basic properties. This is due to the presence in protein molecules of amino acid radicals capable of ionization, as well as free α-amino and α-carboxyl groups at the ends of peptide chains. Acidic properties of the protein are given by acidic amino acids (aspartic, glutamic), and alkaline properties - by basic amino acids (lysine, arginine, histidine).

The charge of a protein molecule depends on the ionization of acidic and basic groups of amino acid radicals. Depending on the ratio of negative and positive groups, the protein molecule as a whole acquires a total positive or negative charge. When a protein solution is acidified, the degree of ionization of anionic groups decreases, while that of cationic groups increases; when alkalized - vice versa. At a certain pH value, the number of positively and negatively charged groups becomes the same, and the isoelectric state of the protein appears (the total charge is 0). The pH value at which the protein is in the isoelectric state is called the isoelectric point and is denoted pI, similar to amino acids. For most proteins, pI lies in the range of 5.5-7.0, which indicates a certain predominance of acidic amino acids in proteins. However, there are also alkaline proteins, for example, salmin - the main protein from salmon milt (pl=12). In addition, there are proteins that have a very low pI value, for example, pepsin, an enzyme of gastric juice (pl=l). At the isoelectric point, proteins are very unstable and precipitate easily, having the least solubility.

If the protein is not in an isoelectric state, then in an electric field its molecules will move towards the cathode or anode, depending on the sign of the total charge and at a speed proportional to its value; this is the essence of the electrophoresis method. This method can separate proteins with different pI values.

Although proteins have buffer properties, their capacity at physiological pH values ​​is limited. The exception is proteins containing a lot of histidine, since only the histidine radical has buffer properties in the pH range of 6-8. There are very few of these proteins. For example, hemoglobin, containing almost 8% histidine, is a powerful intracellular buffer in red blood cells, maintaining the pH of the blood at a constant level.

№5. Physicochemical characteristics proteins.

Proteins have different chemical, physical and biological properties, which are determined by the amino acid composition and spatial organization of each protein. chemical reactions proteins are very diverse, they are due to the presence of NH 2 -, COOH groups and radicals of various nature. These are reactions of nitration, acylation, alkylation, esterification, redox and others. Proteins have acid-base, buffer, colloidal and osmotic properties.

Acid-base properties of proteins

Chemical properties. With weak heating of aqueous solutions of proteins, denaturation occurs. This creates a precipitate.

When proteins are heated with acids, hydrolysis occurs, and a mixture of amino acids is formed.

Physico-chemical properties of proteins

Proteins have a high molecular weight.

The charge of a protein molecule. All proteins have at least one free -NH and -COOH group.

Protein solutions- colloidal solutions with different properties. Proteins are acidic and basic. Acidic proteins contain a lot of glu and asp, which have additional carboxyl and fewer amino groups. There are many lys and args in alkaline proteins. Each protein molecule in an aqueous solution is surrounded by a hydration shell, since proteins have many hydrophilic groups (-COOH, -OH, -NH 2, -SH) due to amino acids. In aqueous solutions, the protein molecule has a charge. The charge of protein in water can change depending on the pH.

Protein precipitation. Proteins have a hydration shell, a charge that prevents sticking. For deposition, it is necessary to remove the hydrate shell and charge.

1. Hydration. The process of hydration means the binding of water by proteins, while they exhibit hydrophilic properties: they swell, their mass and volume increase. Swelling of the protein is accompanied by its partial dissolution. The hydrophilicity of individual proteins depends on their structure. The hydrophilic amide (–CO–NH–, peptide bond), amine (NH2) and carboxyl (COOH) groups present in the composition and located on the surface of the protein macromolecule attract water molecules, strictly orienting them to the surface of the molecule. Surrounding the protein globules, the hydrate (water) shell prevents the stability of protein solutions. At the isoelectric point, proteins have the least ability to bind water; the hydration shell around the protein molecules is destroyed, so they combine to form large aggregates. Aggregation of protein molecules also occurs when they are dehydrated with some organic solvents, such as ethyl alcohol. This leads to the precipitation of proteins. When the pH of the medium changes, the protein macromolecule becomes charged, and its hydration capacity changes.

Precipitation reactions are divided into two types.

Salting out of proteins: (NH 4)SO 4 - only the hydration shell is removed, the protein retains all types of its structure, all bonds, retains its native properties. Such proteins can then be re-dissolved and used.

Precipitation with loss of native protein properties is an irreversible process. The hydration shell and charge are removed from the protein, various properties in the protein are violated. For example, salts of copper, mercury, arsenic, iron, concentrated inorganic acids - HNO 3 , H 2 SO 4 , HCl, organic acids, alkaloids - tannins, mercury iodide. The addition of organic solvents lowers the degree of hydration and leads to precipitation of the protein. Acetone is used as such solvent. Proteins are also precipitated with the help of salts, for example, ammonium sulfate. The principle of this method is based on the fact that with an increase in the salt concentration in the solution, the ionic atmospheres formed by the protein counterions are compressed, which contributes to their convergence to a critical distance, at which the intermolecular forces of van der Waals attraction outweigh the Coulomb forces of repulsion of the counterions. This leads to the adhesion of protein particles and their precipitation.

When boiling, protein molecules begin to move randomly, collide, the charge is removed, and the hydration shell decreases.

To detect proteins in solution, the following are used:

color reactions;

precipitation reactions.

Methods for isolation and purification of proteins.

homogenization- the cells are ground to a homogeneous mass;

extraction of proteins with water or water-salt solutions;

1. salting out;

   electrophoresis;

   chromatography: adsorption, splitting;

   ultracentrifugation.

Structural organization of proteins.

Primary Structure- determined by the sequence of amino acids in the peptide chain, stabilized by covalent peptide bonds (insulin, pepsin, chymotrypsin).

secondary structure- spatial structure of the protein. This is either a spiral or a folding. Hydrogen bonds are created.

Tertiary structure globular and fibrillar proteins. They stabilize hydrogen bonds, electrostatic forces (COO-, NH3+), hydrophobic forces, sulfide bridges, are determined by the primary structure. Globular proteins - all enzymes, hemoglobin, myoglobin. Fibrillar proteins - collagen, myosin, actin.

Quaternary structure- found only in some proteins. Such proteins are built from several peptides. Each peptide has its own primary, secondary, tertiary structure, called protomers. Several protomers join together to form one molecule. One protomer does not function as a protein, but only in conjunction with other protomers.

Example: hemoglobin \u003d -globule + -globule - carries O 2 in the aggregate, and not separately.

Protein can renature. This requires a very short exposure to agents.

6) Methods for detecting proteins.

Proteins are high-molecular biological polymers, the structural (monomeric) units of which are -amino acids. Amino acids in proteins are linked to each other by peptide bonds. the formation of which occurs due to the carboxyl group standing at -carbon atom of one amino acid and -amine group of another amino acid with the release of a water molecule. The monomeric units of proteins are called amino acid residues.

Peptides, polypeptides and proteins differ not only in quantity, composition, but also in the sequence of amino acid residues, physicochemical properties and functions performed in the body. The molecular weight of proteins varies from 6 thousand to 1 million or more. The chemical and physical properties of proteins are due to the chemical nature and physico-chemical properties of the radicals that make up their amino acid residues. Methods for the detection and quantification of proteins in biological objects and food products, as well as their isolation from tissues and biological fluids, are based on the physical and chemical properties of these compounds.

Proteins when interacting with certain chemicals give colored compounds. The formation of these compounds occurs with the participation of amino acid radicals, their specific groups or peptide bonds. Color reactions allow you to set the presence of a protein in a biological object or solution and prove the presence certain amino acids in a protein molecule. On the basis of color reactions, some methods for the quantitative determination of proteins and amino acids have been developed.

Consider universal biuret and ninhydrin reactions, since all proteins give them. Xantoprotein reaction, Fohl reaction and others are specific, since they are due to the radical groups of certain amino acids in the protein molecule.

Color reactions allow you to establish the presence of a protein in the material under study and the presence of certain amino acids in its molecules.

Biuret reaction. The reaction is due to the presence in proteins, peptides, polypeptides peptide bonds, which in an alkaline medium form with copper(II) ions complex compounds colored in purple (with a red or blue tinge) color. The color is due to the presence of at least two groups in the molecule -CO-NH- connected directly to each other or with the participation of a carbon or nitrogen atom.

Copper (II) ions are connected by two ionic bonds with =C─O ˉ groups and four coordination bonds with nitrogen atoms (=N−).

The color intensity depends on the amount of protein in the solution. This makes it possible to use this reaction for the quantitative determination of protein. The color of the colored solutions depends on the length polypeptide chain. Proteins give a blue-violet color; the products of their hydrolysis (poly- and oligopeptides) are red or pink in color. The biuret reaction is given not only by proteins, peptides and polypeptides, but also by biuret (NH 2 -CO-NH-CO-NH 2), oxamide (NH 2 -CO-CO-NH 2), histidine.

The complex compound of copper (II) with peptide groups formed in an alkaline medium has the following structure:

Ninhydrin reaction. In this reaction, solutions of protein, polypeptides, peptides and free α-amino acids, when heated with ninhydrin, give a blue, blue-violet or pink-violet color. The color in this reaction develops due to the α-amino group.

-amino acids react very easily with ninhydrin. Along with them, Rueman's blue-violet is also formed by proteins, peptides, primary amines, ammonia, and some other compounds. Secondary amines, such as proline and hydroxyproline, give a yellow color.

The ninhydrin reaction is widely used to detect and quantify amino acids.

xantoprotein reaction. This reaction indicates the presence of aromatic amino acid residues in proteins - tyrosine, phenylalanine, tryptophan. It is based on the nitration of the benzene ring of the radicals of these amino acids with the formation of yellow-colored nitro compounds (Greek "Xanthos" - yellow). Using tyrosine as an example, this reaction can be described in the form of the following equations.

In an alkaline environment, nitro derivatives of amino acids form salts of the quinoid structure, colored orange. The xantoprotein reaction is given by benzene and its homologues, phenol and other aromatic compounds.

Reactions to amino acids containing a thiol group in a reduced or oxidized state (cysteine, cystine).

Fohl's reaction. When boiled with alkali, sulfur is easily split off from cysteine ​​in the form of hydrogen sulfide, which in an alkaline medium forms sodium sulfide:

In this regard, the reactions for determining thiol-containing amino acids in solution are divided into two stages:

The transition of sulfur from organic to inorganic state

Detection of sulfur in solution

To detect sodium sulfide, lead acetate is used, which, when interacting with sodium hydroxide, turns into its plumbite:

Pb(CH 3 COO) 2 + 2NaOH Pb(ONa) 2 + 2CH 3 COOH

As a result of the interaction of sulfur ions and lead, black or brown lead sulfide is formed:

Na 2 S + Pb(ONa) 2 + 2 H 2 O PbS (black precipitate) + 4NaOH

To determine sulfur-containing amino acids, an equal volume of sodium hydroxide and a few drops of lead acetate solution are added to the test solution. With intensive boiling for 3-5 minutes, the liquid turns black.

The presence of cystine can be determined using this reaction, since cystine is easily reduced to cysteine.

Millon reaction:

This is a reaction to the amino acid tyrosine.

Free phenolic hydroxyls of tyrosine molecules, when interacting with salts, give compounds of the mercury salt of the nitro derivative of tyrosine, colored pinkish red:

Pauli reaction for histidine and tyrosine . The Pauli reaction makes it possible to detect the amino acids histidine and tyrosine in the protein, which form cherry-red complex compounds with diazobenzenesulfonic acid. Diazobenzenesulfonic acid is formed in the reaction of diazotization when sulfanilic acid reacts with sodium nitrite in an acidic medium:

An equal volume of an acidic solution of sulfanilic acid (prepared using hydrochloric acid) and a double volume of sodium nitrite solution are added to the test solution, mixed thoroughly and soda (sodium carbonate) is immediately added. After stirring, the mixture turns cherry red, provided that histidine or tyrosine is present in the test solution.

Adamkevich-Hopkins-Kohl (Schulz-Raspail) reaction to tryptophan (reaction to the indole group). Tryptophan reacts in an acidic environment with aldehydes, forming colored condensation products. The reaction proceeds due to the interaction of the indole ring of tryptophan with aldehyde. It is known that formaldehyde is formed from glyoxylic acid in the presence of sulfuric acid:

R
Solutions containing tryptophan in the presence of glyoxylic and sulfuric acids give a red-violet color.

Glyoxylic acid is always present in small amounts in glacial acetic acid. Therefore, the reaction can be carried out using acetic acid. At the same time, an equal volume of glacial (concentrated) acetic acid is added to the test solution and gently heated until the precipitate dissolves. After cooling, a volume of concentrated sulfuric acid equal to the added volume of glyoxylic acid is added to the mixture carefully along the wall (to avoid mixing liquids). After 5-10 minutes, the formation of a red-violet ring is observed at the interface between the two layers. If you mix the layers, the contents of the dish will evenly turn purple.

To

condensation of tryptophan with formaldehyde:

The condensation product is oxidized to bis-2-tryptophanylcarbinol, which in the presence of mineral acids forms blue-violet salts:

7) Classification of proteins. Methods for studying the amino acid composition.

Strict nomenclature and classification of proteins still does not exist. The names of proteins are given randomly, most often taking into account the source of protein isolation or taking into account its solubility in certain solvents, the shape of the molecule, etc.

Proteins are classified according to composition, particle shape, solubility, amino acid composition, origin, etc.

1. Composition Proteins are divided into two large groups: simple and complex proteins.

Simple (proteins) include proteins that give only amino acids upon hydrolysis (proteinoids, protamines, histones, prolamins, glutelins, globulins, albumins). Examples of simple proteins are silk fibroin, egg serum albumin, pepsin, etc.

Complex (proteids) include proteins composed of a simple protein and an additional (prosthetic) group of non-protein nature. The group of complex proteins is divided into several subgroups depending on the nature of the non-protein component:

Metalloproteins containing in their composition metals (Fe, Cu, Mg, etc.) associated directly with the polypeptide chain;

Phosphoproteins - contain residues of phosphoric acid, which are attached to the protein molecule by ester bonds at the site of the hydroxyl groups of serine, threonine;

Glycoproteins - their prosthetic groups are carbohydrates;

Chromoproteins - consist of a simple protein and a colored non-protein compound associated with it, all chromoproteins are biologically very active; as prosthetic groups, they may contain derivatives of porphyrin, isoalloxazine, and carotene;

Lipoproteins - prosthetic group lipids - triglycerides (fats) and phosphatides;

Nucleoproteins are proteins that consist of a single protein and a nucleic acid linked to it. These proteins play a colossal role in the life of the body and will be discussed below. They are part of any cell, some nucleoproteins exist in nature in the form of special particles with pathogenic activity (viruses).

2. Particle shape- proteins are divided into fibrillar (thread-like) and globular (spherical) (see page 30).

3. By solubility and characteristics of the amino acid composition the following groups of simple proteins are distinguished:

Proteinoids - proteins of supporting tissues (bones, cartilage, ligaments, tendons, hair, nails, skin, etc.). These are mainly fibrillar proteins with a large molecular weight (> 150,000 Da), insoluble in common solvents: water, salt and water-alcohol mixtures. They dissolve only in specific solvents;

Protamines (the simplest proteins) - proteins that are soluble in water and contain 80-90% arginine and a limited set (6-8) of other amino acids, are present in the milk of various fish. Due to the high content of arginine, they have basic properties, their molecular weight is relatively small and is approximately equal to 4000-12000 Da. They are a protein component in the composition of nucleoproteins;

Histones are highly soluble in water and dilute solutions of acids (0.1 N), are distinguished by a high content of amino acids: arginine, lysine and histidine (at least 30%) and therefore have basic properties. These proteins are found in significant amounts in the nuclei of cells as part of nucleoproteins and play an important role in the regulation of nucleic acid metabolism. The molecular weight of histones is small and equal to 11000-24000 Da;

Globulins are proteins that are insoluble in water and saline solutions with a salt concentration of more than 7%. Globulins are completely precipitated at 50% saturation of the solution with ammonium sulfate. These proteins are characterized by a high content of glycine (3.5%), their molecular weight > 100,000 Da. Globulins are weakly acidic or neutral proteins (p1=6-7.3);

Albumins are proteins that are highly soluble in water and strong saline solutions, and the salt concentration (NH 4) 2 S0 4 should not exceed 50% of saturation. At higher concentrations, albumins are salted out. Compared to globulins, these proteins contain three times less glycine and have a molecular weight of 40,000-70,000 Da. Albumins have an excess negative charge and acidic properties (pl=4.7) due to the high content of glutamic acid;

Prolamins are a group of plant proteins found in the gluten of cereals. They are soluble only in 60-80% aqueous solution ethyl alcohol. Prolamins have a characteristic amino acid composition: they contain a lot (20-50%) of glutamic acid and proline (10-15%), which is why they got their name. Their molecular weight is over 100,000 Da;

Glutelins - vegetable proteins are insoluble in water, salt solutions and ethanol, but soluble in dilute (0.1 N) solutions of alkalis and acids. In terms of amino acid composition and molecular weight, they are similar to prolamins, but contain more arginine and less proline.

Methods for studying the amino acid composition

Proteins are broken down into amino acids by enzymes in the digestive juices. Two important conclusions were made: 1) proteins contain amino acids; 2) methods of hydrolysis can be used to study the chemical, in particular amino acid, composition of proteins.

To study the amino acid composition of proteins, a combination of acidic (HCl), alkaline [Ba(OH) 2 ], and, more rarely, enzymatic hydrolysis, or one of them, is used. It has been established that during the hydrolysis of a pure protein that does not contain impurities, 20 different α-amino acids are released. All other amino acids discovered in the tissues of animals, plants and microorganisms (more than 300) exist in nature in a free state or in the form of short peptides or complexes with other organic substances.

The first step in determining the primary structure of proteins is the qualitative and quantitative assessment of the amino acid composition of a given individual protein. It must be remembered that for the study you need to have a certain amount of pure protein, without impurities of other proteins or peptides.

Acid hydrolysis of protein

To determine the amino acid composition, it is necessary to destroy all peptide bonds in the protein. The analyzed protein is hydrolyzed in 6 mol/l HC1 at a temperature of about 110 °C for 24 hours. As a result of this treatment, peptide bonds in the protein are destroyed, and only free amino acids are present in the hydrolyzate. In addition, glutamine and asparagine are hydrolyzed to glutamic and aspartic acids (i.e., the amide bond in the radical is broken and the amino group is cleaved off from them).

Separation of amino acids using ion exchange chromatography

The mixture of amino acids obtained by acid hydrolysis of proteins is separated in a column with a cation exchange resin. Such a synthetic resin contains strongly bound negatively charged groups (for example, sulfonic acid residues -SO 3 -), to which Na + ions are attached (Fig. 1-4).

A mixture of amino acids is introduced into the cation exchanger in an acidic environment (pH 3.0), where the amino acids are mainly cations, i. carry a positive charge. Positively charged amino acids attach to negatively charged resin particles. The greater the total charge of the amino acid, the stronger its bond with the resin. Thus, the amino acids lysine, arginine, and histidine bind most strongly to the cation exchanger, while aspartic and glutamic acids bind the most weakly.

The release of amino acids from the column is carried out by eluting (eluting) them with a buffer solution with increasing ionic strength (ie, with increasing NaCl concentration) and pH. With an increase in pH, amino acids lose a proton, as a result, their positive charge decreases, and hence the bond strength with negatively charged resin particles.

Each amino acid exits the column at a specific pH and ionic strength. By collecting the solution (eluate) from the lower end of the column in the form of small portions, fractions containing individual amino acids can be obtained.

(for more details on "hydrolysis" see question #10)

8) Chemical bonds in the protein structure.

9) The concept of the hierarchy and structural organization of proteins. (see question #12)

10) Protein hydrolysis. Reaction chemistry (stepping, catalysts, reagents, reaction conditions) - a complete description of hydrolysis.

11) Chemical transformations of proteins.

Denaturation and renaturation

When protein solutions are heated to 60-80% or under the action of reagents that destroy non-covalent bonds in proteins, the tertiary (quaternary) and secondary structure of the protein molecule is destroyed, it takes the form of a random random coil to a greater or lesser extent. This process is called denaturation. Acids, alkalis, alcohols, phenols, urea, guanidine chloride, etc. can be used as denaturing reagents. The essence of their action is that they form hydrogen bonds with = NH and = CO - groups of the peptide backbone and with acid groups of amino acid radicals, replacing their own intramolecular hydrogen bonds in the protein, as a result of which the secondary and tertiary structures change. During denaturation, the solubility of the protein decreases, it "coagulates" (for example, when cooking chicken egg), the biological activity of the protein is lost. This is based, for example, on the application aqueous solution carbolic acid (phenol) as an antiseptic. Under certain conditions, with slow cooling of a solution of a denatured protein, renaturation occurs - the restoration of the original (native) conformation. This confirms the fact that the nature of the folding of the peptide chain is determined by the primary structure.

The process of denaturation of an individual protein molecule, leading to the disintegration of its "rigid" three-dimensional structure, is sometimes called the melting of the molecule. Almost any noticeable change in external conditions, such as heating or a significant change in pH, leads to a consistent violation of the quaternary, tertiary and secondary structures of the protein. Usually, denaturation is caused by an increase in temperature, the action of strong acids and alkalis, salts of heavy metals, certain solvents (alcohol), radiation, etc.

Denaturation often leads to the process of aggregation of protein particles into larger ones in a colloidal solution of protein molecules. Visually, this looks, for example, as the formation of a "protein" when frying eggs.

Renaturation is the reverse process of denaturation, in which proteins return to their natural structure. It should be noted that not all proteins are able to renature; in most proteins, denaturation is irreversible. If, during protein denaturation, physicochemical changes are associated with the transition of the polypeptide chain from a densely packed (ordered) state to a disordered state, then during renaturation, the ability of proteins to self-organize is manifested, the path of which is predetermined by the sequence of amino acids in the polypeptide chain, that is, its primary structure determined by hereditary information . in living cells this information, is probably crucial for the transformation of a disordered polypeptide chain during or after its biosynthesis on the ribosome into the structure of a native protein molecule. When double-stranded DNA molecules are heated to a temperature of about 100 ° C, the hydrogen bonds between the bases are broken, and the complementary strands diverge - the DNA denatures. However, upon slow cooling, the complementary strands can reconnect into a regular double helix. This ability of DNA to renature is used to produce artificial DNA hybrid molecules.

Natural protein bodies are endowed with a certain, strictly defined spatial configuration and have a number of characteristic physicochemical and biological properties at physiological temperatures and pH values. Under the influence of various physical and chemical factors, proteins undergo coagulation and precipitate, losing their native properties. Thus, denaturation should be understood as a violation of the general plan of the unique structure of the native protein molecule, mainly its tertiary structure, leading to the loss of its characteristic properties (solubility, electrophoretic mobility, biological activity, etc.). Most proteins denature when their solutions are heated above 50–60°C.

External manifestations of denaturation are reduced to a loss of solubility, especially at the isoelectric point, an increase in the viscosity of protein solutions, an increase in the number of free functional SH-groups, and a change in the nature of X-ray scattering. The most characteristic sign of denaturation is a sharp decrease or complete loss by the protein of its biological activity (catalytic, antigenic or hormonal). During protein denaturation caused by 8M urea or another agent, mostly non-covalent bonds (in particular, hydrophobic interactions and hydrogen bonds) are destroyed. Disulfide bonds are broken in the presence of the reducing agent mercaptoethanol, while the peptide bonds of the backbone of the polypeptide chain itself are not affected. Under these conditions, globules of native protein molecules unfold and random and disordered structures are formed (Fig.)

Denaturation of a protein molecule (scheme).

a - initial state; b - beginning reversible violation of the molecular structure; c - irreversible deployment of the polypeptide chain.

Denaturation and renaturation of ribonuclease (according to Anfinsen).

a - deployment (urea + mercaptoethanol); b - refolding.

1. Protein hydrolysis: H+

[− NH2─CH─ CO─NH─CH─CO − ]n +2nH2O → n NH2 − CH − COOH + n NH2 ─ CH ─ COOH

│ │ ‌‌│ │

Amino acid 1 amino acid 2

2. Precipitation of proteins:

a) reversible

Protein in solution ↔ protein precipitate. Occurs under the action of solutions of salts Na+, K+

b) irreversible (denaturation)

During denaturation under the action external factors(temperature; mechanical action - pressure, rubbing, shaking, ultrasound; the action of chemical agents - acids, alkalis, etc.) there is a change in the secondary, tertiary and quaternary structures of the protein macromolecule, i.e. its native spatial structure. The primary structure, and, consequently, the chemical composition of the protein does not change.

During denaturation, the physical properties of proteins change: solubility decreases, biological activity is lost. At the same time, the activity of some chemical groups increases, the effect of proteolytic enzymes on proteins is facilitated, and, consequently, it is more easily hydrolyzed.

For example, albumin - egg white - at a temperature of 60-70 ° is precipitated from a solution (coagulates), losing the ability to dissolve in water.

Scheme of the process of protein denaturation (destruction of the tertiary and secondary structures of protein molecules)

3. Burning proteins

Proteins burn with the formation of nitrogen, carbon dioxide, water, and some other substances. Burning is accompanied by the characteristic smell of burnt feathers.

4. Color (qualitative) reactions to proteins:

a) xantoprotein reaction (for amino acid residues containing benzene rings):

Protein + HNO3 (conc.) → yellow color

b) biuret reaction (for peptide bonds):

Protein + CuSO4 (sat) + NaOH (conc) → bright purple color

c) cysteine ​​reaction (for amino acid residues containing sulfur):

Protein + NaOH + Pb(CH3COO)2 → Black staining

Proteins are the basis of all life on Earth and perform various functions in organisms.

Salting out proteins

Salting out is the process of isolating proteins from aqueous solutions with neutral solutions of concentrated salts of alkali and alkaline earth metals. When high concentrations of salts are added to the protein solution, the dehydration of the protein particles and the removal of the charge occur, while the proteins precipitate. The degree of protein precipitation depends on the ionic strength of the precipitant solution, the size of the particles of the protein molecule, the magnitude of its charge, and hydrophilicity. Different proteins precipitate at different salt concentrations. Therefore, in sediments obtained by gradually increasing the concentration of salts, individual proteins are in different fractions. Salting out of proteins is a reversible process, and after the salt is removed, the protein regains its natural properties. Therefore, salting out is used in clinical practice in the separation of blood serum proteins, as well as in the isolation and purification of various proteins.

Added anions and cations destroy the hydrated protein shell of proteins, which is one of the stability factors of protein solutions. Most often, solutions of Na and ammonium sulfates are used. Many proteins differ in the size of the hydration shell and the magnitude of the charge. Each protein has its own salting out zone. After removal of the salting out agent, the protein retains its biological activity and physicochemical properties. In clinical practice, the salting out method is used to separate globulins (with the addition of 50% ammonium sulfate (NH4)2SO4 a precipitate forms) and albumins (with the addition of 100% ammonium sulfate (NH4)2SO4 a precipitate forms).

Salting out is influenced by:

1) nature and concentration of salt;

2) pH environments;

3) temperature.

The main role is played by the valencies of the ions.

12) Features of the organization of the primary, secondary, tertiary structure of the protein.

At present, the existence of four levels of structural organization of a protein molecule has been experimentally proven: primary, secondary, tertiary and quaternary structure.

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 tuber, 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 happens to the protein (for example, a chicken egg) if it is heated-fried?(slide number 2)

(Suggested answer: color, density, smell, taste will change) Chemistry teacher: Moreover, the same changes occur with the protein if it is affected by salts of 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. Findings:

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). The primary structure, and, consequently, the chemical composition of the protein does 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. Solve a problem : It is known that an adult needs 1.5 g of protein per 1 kg of body weight per day. Knowing your weight, determine the daily rate of protein intake for your body.

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 carbohydrates provide us Agriculture, and it is possible to increase the supply of dietary fats at least by refusing to use it 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 into a test tube nitric acid and with a pipette carefully add the protein solution along the wall of the test tube 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 much more high-calorie coal, or even more so with 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. AT last case only solid or semi-solid 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, of course, are also not suitable for this.
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 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 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 of margarine are obtained - confectionery and creamy. 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 found 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.
Remarkable advances have been made in protein synthesis in recent years. 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. ).
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 the hydrolysis of the protein, 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 an earthenware pot, mix finely chopped or mashed vegetables and spices, for example, 20 g of celery, 15 g of 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 the waste of processing 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 of table salt crushed to the smallest powder, 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 will 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 stain 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. So be careful with city gas and other gases containing carbon monoxide!
We now know that blood plays a vital role in metabolism. vehicle. Gas transport, removal of 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 every hour, the contents of the glass will be stirred 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 tint 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.
Unpleasant sour smell 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, rapidly 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.