Place 1-2 drops of vegetable oil (or other fat) in five test tubes. Pour 1 ml of ethyl alcohol into the first test tube, ethyl ether into the second, gasoline into the third, benzene into the fourth, and water into the fifth. Shake the contents of the tubes and let stand.

Does fat dissolve in all substances? Which substances are good fat dissolvers and which are bad? What conclusion can be drawn about the solubility of fats based on experience.

Output example.

1. Sunflower oil + water = the formation of an unstable emulsion, followed by a rapid separation of the mixture into two layers.
2. sunflower oil + ethyl alcohol = formation of a cloudy solution as a result of insufficient dissolution of the oil.

3. sunflower oil + benzene = the solution is almost transparent.

4. sunflower oil + gasoline = transparent solution. oil is completely soluble in gasoline

Completely soluble in ethyl ether

Vegetable oil, being non-polar, dissolves in non-polar solvents, i.e., in gasoline, ethyl ether

Water and alcohol are polar solvents; fat is poorly or practically insoluble in them.

Experience No. 2. Emulsification of fats. (Form the answer yourself if you have a hint)

Pour 3-4 drops of vegetable oil into five test tubes. Add 5 ml of water to the first test tube, 5% NaOH solution to the second, soda solution to the third, soap solution to the fourth, protein solution to the fifth. Shake the contents of each tube vigorously and observe the formation of an emulsion. Place the test tubes with the resulting emulsions in a rack for a few minutes.

In which test tube did separation occur? What substances give stable emulsions?

emulsion called a dispersion system consisting of two or more liquid phases, one of which (called the dispersion medium) is continuous.
If you take approximately the same amount of oil and water and mechanically, for example, with stirring, prepare an emulsion, then after that a rapid separation will occur.

The formation of stable emulsions occurs when a surfactant is added.

Experience No. 3. Saponification of fats in a water-alcohol solution of alkali. (Video demonstration) Brief description of the experience.

Place 2 g of fat in a test tube and add 6 ml of a 15% alkali alcohol solution. Stir the mixture with a glass rod, fix the test tube in a rack and stopper under reflux. Place the test tube with the mixture in a water bath and heat for 12-15 minutes until boiling. Saponification is carried out until the liquid becomes homogeneous. To determine the end of saponification, pour a few drops of the resulting mixture into a test tube, add 6 ml of water and heat the solution. If the taken mixture dissolves in water without droplets of fat, then saponification can be considered complete. If there are drops of fat in the solution, then continue heating the mixture in a water bath for a few more minutes.

Add a saturated solution of NaOH to the resulting thick liquid. The liquid becomes cloudy and a layer of soap is released that floats to the surface. Let the mixture stand and cool the test tube with cold water, remove the resulting soap and leave for the next experiments.

Questions for self-examination: (answers in a notebook for highlighted questions)

1. What substances are fats?

2. What is the role of fats in the body?

3. What process is called rancidity?

4. Compare vegetable oils and animal fats in composition, properties and

application.

5. Describe methods for obtaining animal fats and vegetable oils.

6. What is a surfactant?

What types of surfactants are divided into by the nature of hydrophilic and hydrophobic groups?

What type of surfactant is ordinary soap?

9. What is liquid soap (detergents), solid soap? (Cosmetic and laundry soaps)

10. Write the reaction equations for the synthesis of fats from: a) palmitic acid and

glycerin; b) linoleic acid and glycerin. Name the resulting fats.

11. Make the equations for the reactions of obtaining: a) oleolinoleopalmitin; b) butyric acid triglyceride; c) diolostearin.

12. Describe all the changes that occur with fats during the technological processing of food.

"Hydrolysis of carbohydrates, denaturation of proteins".

A) Carbohydrates (Text to read and repeat)

Carbohydrates (sugars) are common in nature and play an important role in human life. They make up to 80% of the mass of dry matter of plants and about 2% of the dry matter of animal organisms.

The name carbohydrates arose due to the fact that at first substances were known whose composition could be expressed by the formula Cn (H 2 O) m.

Monosaccharides are polyhydric aldehyde or keto alcohols.

Polysaccharides are divided into sugar-like (oligosaccharides) and non-sugar-like. Low molecular weight (sugar-like) polysaccharides contain a small number (2-10) of monosyl residues in the molecule. They dissolve well in water, have a sweet taste and a pronounced crystalline structure. Some of them (maltose, lactose) reduce copper (P) ions (Fehling's liquid), they are called reducing, others (sucrose, trehalose) do not reduce, and therefore they are classified as non-reducing oligosaccharides.

High-molecular (non-sugar-like) polysaccharides contain from tens to several tens of thousands of monosaccharide residues; they are insoluble in water, tasteless and do not have a pronounced crystalline structure.

Of the monosaccharides, glucose and fructose are the most important.

Glucose (C 6 H 12 O 6) is a colorless crystalline substance that is soluble in water.

The study of the structure and properties showed that glucose can exist in various forms: aldehyde and two cyclic forms.

Glucose is found in many fruits and berries (grapes) and is formed in the body during the breakdown of disaccharides and starch in food. It is quickly and easily absorbed from the intestines into the blood and is used by the body as an energy source for the formation of glycogen in the liver, to nourish the tissues of the brain, muscles and maintain the required level of sugar in the blood.

Under the action of enzymes, glucose is fermented.

Lipids.

organic substances.

Fats and lipoids also perform a building function; they are part of cell membranes. Due to poor thermal conductivity, fat is capable of a protective function. In some animals (seals, whales), it is deposited in the subcutaneous adipose tissue, forming a layer up to 1 m thick. The formation of some lipoids precedes the synthesis of a number of hormones. Consequently, these substances also have the function of regulating metabolic processes.

Fats and lipoids.

Double-stranded RNAs differ in structure. Double-stranded RNAs are the keepers of genetic information in a number of viruses, i.e. perform the functions of chromosomes. Single-stranded RNAs carry out the transfer of information about the structure of proteins from the chromosome to the site of their synthesis and participate in protein synthesis.

There are several types of single-stranded RNA. Their names are due to their function or location in the cell. Most of the cytoplasmic RNA (up to 80-90%) is ribosomal RNA (rRNA) contained in ribosomes. rRNA molecules are relatively small and consist of an average of 10 nucleotides. Another type of RNA (mRNA) that carries information about the sequence of amino acids in proteins to be synthesized to ribosomes. The size of these RNAs depends on the length of the DNA segment from which they were synthesized. Transfer RNAs perform several functions. They deliver amino acids to the site of protein synthesis, "recognize" (according to the principle of complementarity) the triplet and RNA corresponding to the transferred amino acid, and carry out the exact orientation of the amino acid on the ribosome.

Fats are compounds of fatty macromolecular acids and the trihydric alcohol glycerol. Fats do not dissolve in water - they are hydrophobic. There are always other complex hydrophobic fat-like substances in the cell, called lipoids.

One of the main functions of fats is energy. The fat content in the cell ranges from 5-15% of the dry matter mass. In the cells of living tissue, the amount of fat increases to 90%. Accumulating in the cells of adipose tissue of animals, in the seeds and fruits of plants, fat serves as a reserve source of energy.

They make up 20 - 30% of the composition of the cell. They can be simple (amino acids, glucose, fatty acids) and complex (proteins, polysaccharides, IC, lipids).

NUCLEIC ACIDS (polynucleotides), biopolymers that store and transfer genetic. information in all living organisms, as well as those involved in the biosynthesis of proteins. The primary structure of nucleic acids is a sequence of nucleotide residues. The latter in the nucleic acid molecule form unbranched chains. Depending on the nature of the carbohydrate residue in the nucleotide (D-deoxyribose or D-ribose), nucleic acids are divided respectively. on deoxyribonucleic (DNA) and ribonucleic (RNA) to-you.

DNA is the largest biopolymer containing up to 108-109 monomers - deoxyribonucleotides, which contain sugar - deoxyribose. DNA contains 4 types of deoxyribonucleotides: adenine - A, thymidine - T, guanine - G, cytosine - C.

§ 5. Triacylglycerols and fatty acids

Triacylglycerols are the most abundant lipids in nature. They are usually divided into fats and oils. Fats are solid at room temperature. When heated, they melt and turn into a liquid state. Oils are liquid at room temperature. Fats and oils do not dissolve in water. When vigorously mixed with water, they form emulsions.

In modern developed countries, fats in the diet of people account for up to 45% of total energy consumption. Such a large proportion of fat with limited movement is undesirable. The cause of many more and more widespread diseases, primarily diseases of the cardiovascular system, is the excess content of fats in food. At the same time, in many developing countries, on the contrary, there is not enough fat in food; in the total energy consumption, they account for no more than 10%.

Triacylglycerols play an important role in the body of an animal or plant. So, for example, the share of triacylglycerols in the human body accounts for about 10% of body weight (Fig. 4).

Rice. 4. The chemical composition of the human body.

Fats are the most efficient means of storing energy, as they have special advantages over other compounds. They do not dissolve in water, so they do not significantly change the physicochemical properties of the cytoplasm; moreover, they are chemically inert. And most importantly, their energy content is much higher than the energy content of other substances, such as carbohydrates and proteins. A limited amount of energy can also be stored in the form of carbohydrates (glycogen), but most of the excess energy supplied to the body is stored mainly in the form of fats. Almost all food products contain fats, although their content varies widely (Table 1).

Table 1

Average fat content of some foodstuff.

food product	Mass of fat in 100 g food product, g	food product	Mass of fat in 100 g food product, g
Butter	25 – 45 10,9 17,7 82,0	Sunflower oil Potato roasted peanuts White bread	99,9 49,0 1,7

Triacylglycerols

Triacylglycerols (fats and fatty oils of natural origin) are esters formed from glycerol and fatty acids. Fatty acids are the common name for the monobasic aliphatic carboxylic acids RCOOH. Hydrolysis of triacylglycerols produces glycerol and fatty acids:

The composition of triacylglycerol can include residues of both the same acid - such fats are called simple - and different (mixed fats). Fatty acids, depending on the structure of the radical, can be divided into rich, unsaturated, as well as branched And cyclic.

Saturated fatty acids have the general formula CH 3 (CH 2) n COOH, in which n can vary from 2 to 20 and slightly higher. An example of a short chain acid is butyric acid CH 3 (CH 2) 2 COOH, which is found in milk fat and butter. Examples of long chain acids are palmitic CH 3 (CH 2) 14 COOH and stearic CH 3 (CH 2) 16 COOH. They are part of the triacylglycerols of almost all fats and oils of animal and vegetable origin.

Unsaturated fatty acids contain one or more double bonds in the aliphytic chain, which can also be short or long. One of the most common acids in nature is oleic acid. It is found in olive oil, from which its name comes, as well as in pork fat CH 3 (CH 2) 7 CH \u003d CH (CH 2) 7 COOH. The double bond in oleic acid has cis-configuration. In nature, there are fatty acids with a large number of double bonds, for example, linoleic (two double bonds), linolenic (three double bonds), arachidonic (four double bonds).

Triacylglycerols containing short chain or highly unsaturated fatty acids tend to have lower melting points. Therefore, at room temperature, they are in the form of oils. This is characteristic of triacylglycerols of plant origin, which contain a large proportion of unsaturated acids. In contrast, animal fats are characterized by a high content of saturated fatty acids and are generally solid. This can be seen by comparing the composition of olive oil (vegetable oil) and butter (animal fat) (Table 2).

Table 2.

Distribution of fatty acids in olive and butter oils

fatty acid type	Number of carbon atoms
		in olive oil	in butter
Saturated
Total 12 61
Unsaturated
Total 84 33

Interesting to know! In the cells of warm-blooded animals, the content of unsaturated fatty acids is lower than in the cells of cold-blooded animals.

Margarine is a substitute for butter. It is obtained by hydrogenation of vegetable oils over a nickel catalyst. Double bonds found in the residues of unsaturated acids add hydrogen. As a result, unsaturated fatty acids are converted into saturated ones. By changing the degree of hydrogenation, hard and soft margarines can be obtained. Additionally, fat-soluble vitamins are added to margarine, as well as special substances that give margarine color, smell, and stability.

branched And cyclic fatty acids are rare in nature. Chaulmugric acid is an example of cyclic fatty acids, and tuberculostearic acid is an example of branched fatty acids:

Soaps

Soaps are sodium or potassium salts of long chain fatty acids. They are formed by boiling animal fat or vegetable oil with sodium or potassium hydroxide.

This process has been named saponification. Potassium soap is softer, often liquid, than sodium soap.

The cleansing effect of soap is due to the fact that soap anions have an affinity for both oily contaminants and water. The anionic carboxyl group has an affinity for water, with the molecules of which it forms hydrogen bonds, i.e. it is hydrophilic. The hydrocarbon chain, due to hydrophobic interactions, has an affinity for fatty pollutants. The hydrophobic tail of a soap molecule dissolves in a drop of dirt, leaving a hydrophilic head on the surface. The surface of a drop of dirt begins to actively interact with water and eventually breaks away from the fiber and passes into the water phase (Fig. 5).

Fig.5. Detergent effect of soap: 1 - hydrocarbon chains of soap anions dissolve in greasy mud, 2 - microdroplet of mud (micelle) suspended in water

Interacting with calcium ions, which are contained in hard water, soaps form water-insoluble calcium salts:

As a result, the soap falls out in the form of flakes and is wasted.

In recent decades, synthetic detergents have become widespread. In their molecules, often instead of a carboxyl group, there is a sulfo group R-SO 3 Na. Calcium salts of sulfonic acids are soluble in water.

Interesting to know! Natural fatty acids are usually straight chain with an even number of carbon atoms. Synthetic detergents contain branched chains that are difficult for bacteria to break down. This leads to significant pollution of natural water bodies, where household waste eventually ends up. Until recently, another problem with washing powders was their high content (up to 30%) of inorganic phosphates. Phosphates are a good breeding ground for certain algae. Therefore, the ingress of a large amount of phosphates into water bodies causes the rapid growth of these algae, which intensively absorb oxygen dissolved in water. With a lack of oxygen, a massive death of aquatic plants and animals occurs, followed by their decomposition. As a result, the pond becomes swampy.

Rancidity of fats

Fats during storage under the influence of light and oxygen acquire an unpleasant odor and taste. This process is called rancidity. As a result, fat is oxidized. Unsaturated fatty acids are most easily oxidized:

The resulting products have an unpleasant odor and taste. To prevent rancidity, fats should be stored in the dark without oxygen and at low temperatures.

Breakdown and synthesis of fats in the body

Digestion of fats begins in the stomach and continues in the intestines. This process requires bile acids, with their participation, emulsification of fats occurs. Emulsified fats are broken down lipases. The hydrolysis of fats proceeds in several stages:

The hydrolysis of triacylglycerols in the first and second stages proceeds rapidly, while the hydrolysis of monoacylglycerols proceeds more slowly. As a result of hydrolysis, a mixture is formed containing fatty acids, mono-, di-, triacylglycerols, which are absorbed by intestinal epithelial cells. These cells resynthesize lipids, which then enter other tissues, where they are stored or oxidized. As a result of the oxidation of fats, water and carbon monoxide (IV) are formed, and the released energy is stored in the form of ATP. When 1 g fat is oxidized, 39 kJ of energy is released.

Answer from Elena Kazakova[guru]
They are hydrophobic.
Hydrophobic molecules surrounded by water tend to get closer, because in this case the structure of water, stabilized by hydrogen bonds, is disturbed to the least extent. In this case, the total surface area wetted by water is the smallest.

Answer from Yustas[guru]
Because fats are hydrophobes for the most part. After all, small parts of molecules interact with water with hydrophobes, so, accordingly, they partially dissolve, but not completely, but poor interaction due to the small angle of interaction between water and a fat molecule)

Answer from Aka Diesel[guru]
Because nope!

Answer from Krosh[newbie]
Fat is lighter than water!

Answer from Serserkov[guru]
Water is a polar solvent, it dissolves substances with a polar molecular structure. Fats are non-polar. hence their hydrophobicity. In fact, they dissolve, but very poorly.

Answer from Elena Yashina[active]
The water is human, the fat is God's. "Give it to God" (Pentateuch of Moses, it seems Leviticus). Water is a symbol of repentance, John the Baptist, the best of men. Oil, oil symbol of God. The interaction of God and man, Under the influence of the sun, fire (the Word of God is fire), water breaks up rises to heaven, turns into clouds, again into water and falls to the ground either in the form of fertile rain, watering dry land, or irrigating again and again fertile land , or in the form of more formidable rainfall, punishing the wicked if necessary. Water above, in the sky, and water below on earth, in the earth. Just the other day, I had a constellation in my mind: according to the Old Testament, when God's people walked together according to the action of God through Moses, the water parted, and the sea, and already before entering the Promised Land, the river. They went dry. According to the New Testament in John the Baptist, through repentance before God, we promise God a good conscience before God in every person. That is, the water remains around me, then suddenly the Lord comes (Malachi 3.1), and then I in Jesus (God in me, I and God are one) already walk on the water: that is, those who think not like God already according to me, pagans (goyim, peoples not of God), who do not have the truth of God, which means the power of God. And in Christ Jesus, indeed, God's people are united into one Body of the Lord, as someone before me answered, oil is united into one. Wrong reason can no longer prevent me from doing right. That is, "the law did not bring anything to perfection, but a better hope is being introduced." The water cycle in nature prolongs life on earth, giving it new colors of the rainbow. After all, with a rainbow, God confirmed his promise that there would be no more global flood (Genesis 9 chapter). Even in the Old Testament, the coming of Jesus was promised. And now we live a new life. "Behold, I make all things new", "Whoever is in Christ, he is a new creation (creation)."