Place 1-2 drops of vegetable oil (or other fat) in four test tubes. Pour 1 ml of ethyl ether into the first test tube, 1 ml of ethyl alcohol into the second, 1 ml of gasoline into the third, and 1 ml of water into the fourth. Shake the contents of the tubes and let stand. Did fat dissolve in each tube? Which substances are good fat dissolvers and which are bad? Why? What conclusion about the solubility of fats can be drawn from experience?
Output:
Experience No. 6 Addition of bromine to oleic acid
Add 3-4 drops of bromine water and 1 drop of oleic acid to the test tube and shake vigorously. Bromine water becomes colorless.
(CH 3) - (CH 2) 7 -CH \u003d CH- (CH 2) 7 - COOH + Br 2 → (CH 3) - (CH 2) 7 -CHBr -CHBr - (CH 2) 7 - COOH
(dibromostearic acid)
Experiment No. 7 Oxidation of oleic acid with potassium permanganate
Place 2 drops of oleic acid, sodium carbonate solution and potassium permanganate solution into a test tube. When the mixture is shaken, the pink color disappears. what does the decolorization of bromine water and potassium permanganate solution indicate?
output:
(CH 3) - (CH 2) 7 -CH \u003d CH- (CH 2) 7 -COOH + [O] + NOH → (CH 3) - (CH 2) 7 -CH - CH - (CH 2) 7 - UNSD
dihydroxystearic acid
Experiment No. 8 Dissolving soap in water.
A piece of soap (about 10 mg) is placed in a test tube, 5 drops of water are added and the contents of the test tube are thoroughly shaken for 1-2 minutes. After that, the contents of the test tube are heated in the flame of a burner. Sodium and other alkaline soaps (potassium, ammonium) dissolve well in water.
Control questions on the topic "Carboxylic acids":
1 Carry out the following transformations: C 2 H 6 → C 2 H 5 Cl → C 2 H 5 OH → CH 3 COOH → CH 3 COOH
2. How many grams of magnesium and acetic acid will be required to produce 6 liters of hydrogen.
3. Write the equations for the reactions of obtaining succinic acid from monochloroacetic acid?
4. Write the reaction equations and name the resulting compounds:
a) lactic acid + ethanol
b) lactic acid + sodium hydroxide
c) lactic acid + acetic acid
5. Write the structural formula of palmitodistearin
Laboratory work No. 9 Amino acids. Squirrels.
The composition of proteins includes carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus and other elements. The molecular weight of a protein can reach hundreds of thousands of carbon units. Proteins are unstable compounds, they are well hydrolyzed under the influence of acids, alkalis or enzymes. The end products of protein breakdown are amino acids of various compositions.
Amino acids can be considered as derivatives carboxylic acids, in which the hydrogen atom in the radical is replaced by an amino group:
Amino acids simultaneously have two types of functional groups: carboxyl, which is a carrier acid properties, and an amino group - a carrier of basic properties. Amino acids exhibit amphoteric properties, that is, the properties of both acids and bases, so proteins also exhibit amphoteric properties, since they are built from amino acid residues.
Proteins dissolve in various solvents. Many proteins dissolve in water, some in solutions of neutral salts, in alkalis or acids.
Under certain conditions, proteins are able to precipitate, and the precipitation can be reversible and irreversible. The ability of proteins to precipitate under various conditions is used to detect and separate them. Protein color tests are also used to detect proteins. These include xantoprotein, biuret and other reactions.
Reagents. protein solution; aminoacetic acid solution; sulphuric acid(conc.); nitric acid (conc.); hydrochloric acid (conc.); sodium hydroxide, 20% solution; lead acetate, 10 and 20% solutions; copper sulfate (saturated and 1% solutions) CuSO 4 ; ammonia (conc.) NH 3; sodium chloride NaCl, 10% solution; ammonium sulfate, saturated solution(NH 4) 2 SO 4; phenolphthalein; litmus paper, methyl orange; litmus red. aminoacetic acid, 0.2n. solution; copper (II) oxide CuO, powder; caustic soda, 2 n. NaOH solution.
Equipment. dry test tube; glass rod, test tube with gas tube.
Experience number 1.The formation of copper salt aminoacetic acids
Reagents and materials:
A little copper oxide CuO powder, 4 drops of aminoacetic acid solution are placed in a test tube and heated in a burner flame, shaking the contents of the test tube. The tube is placed for some time in a tripod so that the excess of black copper oxide powder settles. To the settled blue solution, add 1 drop of sodium hydroxide solution. The solution remains clear.
Amino acids are characterized by the formation of copper salts, colored in blue color.
α-Amino acids give colored internal complex salts with copper, very stable:
An experienceNo. 2. The effect of amino acids on indicators
Pour 0.5 ml of aminoacetic acid solution into three test tubes and add phenolphthalein to the first, methyl orange to the second, and litmus to the third. The color of indicators does not change Why are aqueous solutions of monoamino acids neutral with respect to indicators?
Output:
An experienceNo. 3. Protein coagulation on heating
A small amount of protein solution is placed in a test tube and heated to a boil in a burner flame. Watch the protein fall out in the form of flakes or turbidity. How is this explained? Dilute the solution with water. Does the precipitate dissolve? if not, why not? Cool the protein solution slightly for use in the next experiment.
Output:
Experience No.4. Salting out proteins with sulfateammonium
Pour 1-1.5 ml of a solution of protein and ammonium sulfate into a test tube and shake the mixture, heat to a boil in a burner flame. The liquid becomes cloudy, and the amount of coagulated protein increases dramatically. the addition of neutral salts facilitates and accelerates the coagulation of proteins when heated. protein folding is a process of irreversible precipitation, since protein molecules change their structure in the process.
An experienceNo. 5. Precipitation of proteins with salts of heavymetals
Pour 1-2 ml of the protein solution into two test tubes and slowly, drop by drop, while shaking, pour into one of them a saturated solution of copper sulfate, and into the other a 20% solution of lead acetate. A flaky precipitate or turbidity is formed. Heavy metal salts precipitate proteins from solutions, forming water-insoluble salt-forming compounds, with copper salts - a blue precipitate, with lead salts - white.
An experienceNo. 6. Precipitation of proteins by mineralacids
Pour 1 ml of the protein solution into three test tubes. Carefully add concentrated nitric acid to the protein solution so that the acid does not mix with the protein. A ring of white flocculent sediment forms at the point of contact between the two liquids. Repeat this experiment with concentrated sulfuric and hydrochloric acids. Proteins form salt-like compounds with concentrated acids and at the same time cause protein coagulation. in most cases the precipitate formed is soluble in an excess of concentrated acids (except nitric acid).
An experienceNo. 7. Color reactions for proteins
1 xantoprotein reaction. The xantoprotein reaction indicates the presence in the protein of amino acids containing benzene nuclei, such as tyrosine. When such amino acids react with nitric acid, yellow nitro compounds are formed.
Add 5-6 drops of concentrated nitric acid to 1 ml of protein solution until a white precipitate or turbidity from coagulated protein appears. Heat the reaction mixture until the precipitate turns yellow. During hydrolysis, the precipitate dissolves. Cool the mixture and add to it carefully, drop by drop, an excess of concentrated NaOH sodium hydroxide solution. The color changes to orange, which indicates the formation of more intensely colored anions.
2 biuret reaction. Using the biuret reaction, the presence of peptide groups (-CO-NH-) in protein molecules is detected. Proteins with copper salts give a red-violet color due to the formation of complex compounds.
Pour 1-2 ml of a protein solution, 20% sodium hydroxide into a test tube. Then add 3-4 drops of a dilute, almost colorless solution of copper sulphate (CuSO * 5H 2 O) and mix the contents thoroughly. The liquid turns purple.
Control questions on the topic "Amino acids"
1. Briefly describe each structure of a protein molecule.
2..Make a diagram that reflects the transformation of food proteins in the human body.
3. Briefly describe the use of proteins.
4. What determines the specific biological activity of a protein molecule? In what cases can it be lost?
5. What types of protein hydrolysis do you know?
LABORATORY WORK №10.PROPERTIESMONOSACCHARIDES
In relation to hydrolysis, carbohydrates are divided into two main classes: simple carbohydrates, or monosaccharides (glucose, fructose, galactose), and complex sugars, or polysaccharides. Complex carbohydrates, in turn, are divided into two main groups: sugar-like (sucrose, lactose, maltose) and non-sugar-like carbohydrates (starch, fiber). Of the monosaccharides, glucose and fructose are of the greatest importance, the chemical properties of which are determined by the peculiarity of their structure. Sugar-like complex carbohydrates have a sweet taste, dissolve in water, and break down into monosaccharides upon hydrolysis. Non-sugar-like complex carbohydrates do not have a sweet taste; upon hydrolysis, they also break down into monosaccharides.
Reagents. Glucose, 20% and 2% solutions; Selivanov's reagent; crystalline sucrose and 10% freshly prepared solution; lactose, 10% solution; Fehling's liquid (I); sulfuric acid, 10% solution; ammonia solution, 2.5% NH 3 *H 2 O; sodium hydroxide NaOH, 1% solution; silver nitrate, 1% AgNO 3 solution;
Equipment. Glass with a capacity of 100 ml; water bath; funnel; filter paper; .
Experience number 1. Oxidation glucose with ammonia solution silver oxide (silver mirror reaction)
Pour 1-2 ml of ammonia solution into a test tube and add 1 ml of AgNO 3 silver nitrate; first, a brown precipitate of silver oxide precipitates, which then dissolves in an excess of ammonia solution ([Ag (NH 3) 2 ]OH). To the prepared ammonia solution of silver oxide, add 2 ml of a 20% glucose solution and a few drops of 2% sodium hydroxide and gently heat the resulting mixture until the solution begins to turn black. Further, the reaction proceeds without heating and metallic silver is released on the walls of the test tube in the form of a mirror coating.
glucose gluconic acid
An experience No. 2. Oxidation of glucose with Fehling's reagent
3 drops of glucose solution and a drop of Fehling's reagent are injected into the test tube. Holding the tube at an angle, gently heat the top of the solution. in this case, the heated part of the solution turns orange-yellow due to the formation of copper (I) hydroxide, which subsequently turns into a red precipitate of copper (I) oxide Cu 2 O.
oxidation with Fehling's reagent serves as a qualitative reaction for glucose.
The task: write the equation for this reaction and draw the conclusion
Experience No. 3 Refining glucose with alkali
4 drops of glucose solution are placed in a test tube and 2 drops of sodium hydroxide solution are added. heat the mixture to a boil and gently boil for 2-3 minutes. The solution turns yellow and then turns dark brown. When heated with alkalis, monosaccharides are resinous and turn brown. the process of resinification leads to the formation of a complex mixture of substances.
Experience No. 4 Selivanov's reaction to ketosis
A crystal of resorcinol, 2 drops of hydrochloric acid and 2 drops of a fructose solution are placed in a test tube. The contents of the test tube are heated until boiling begins. liquid gradually turns red.
When heated with concentrated mineral acids, hexose molecules gradually split, forming a mixture of various products (hydroxymethylfurfural is also one of the products), which forms a colored compound with resorcinol. this reaction makes it possible to quickly detect the presence of ketohexoses in a mixture of sugars.
Control questions on the topic "Properties of monosaccharides and disaccharides"
What compounds are called monosaccharides?
Based on what experiments can one draw a conclusion about the structure of glucose?
During alcoholic fermentation of glucose, 112 liters of CO 2 were released. How much ethyl alcohol did you get and how much glucose did it take?
4. Using the text of the textbook paragraph, prepare written answers to the following questions: a) What are the physical properties of glucose? b) Where is glucose found in nature? c) What is the molecular formula of glucose
5. Which monosaccharides are called pentoses, and which hexoses?
6. Which forms of sugars are called furanose and which are pyranose
7. What features underlie the definition of right and left isomers of sugars by their chemical stringing?
LABORATORY WORK №11 PROPERTIESPOLYSACCHARIDES
Reagents. Starch, powder and solution; sucrose solution; potato; Rye bread; potato; iodine solution; sulfuric acid, 20% solution of H 2 SO 4 I (conc.); sodium carbonate Na 2 CO 3 ; calcium carbonate CaCO 3;; ammonia, 1% solution of NH 3 * H 2 O; Fehling's liquid (I);
Equipment. Glass with a capacity of 100 ml; funnel; water bath; porcelain cups - 2 PCS.; mortar and pestle; glass rod, filter paper; cotton wool
Experience No. 1. Interaction of starch with iodine. Qualitative reaction to starch.
Place 2 drops of starch paste and 1 drop of iodine solution into a test tube. The contents of the tube turn blue. The resulting dark blue liquid is heated to a boil. The color disappears, but reappears on cooling.
Starch is a mixture of two polysaccharides - amylose (20%) and amylopectin (80%). Amylose is soluble in warm water and gives a blue color with iodine. Both amylose and amylopectin are composed of glucose residues linked by α-glycosidic bonds, but they differ in the shape of the molecules. Amylose is a linear polysaccharide built from several
Amylopectin is insoluble in warm water, swells in it, forming a starch paste. Amylopectin, unlike amylose, contains branched chains of glucose residues. Amylopectin with iodine gives a reddish-violet color.
Obtaining starch paste.
We dilute 12 g of starch in 40 ml of cold water until starch milk is obtained. Bring 160 ml of water to a boil, pouring starch milk into it while stirring. bring the resulting starch paste to a boil and cool to room temperature
Experience number 2. Updatestarch reduction in bread and potatoes.
Place one drop of iodine on a slice of white bread and on a slice of raw potatoes. How will the color change? Make a conclusion.
An experience№3. Evidence for the presence of hydroxyl groups in sucrose
Place 1 drop of sucrose solution, 5 drops of alkali solution and 4-5 drops of water into a test tube. Add a drop of copper(II) sulfate solution. The mixture acquires a faint bluish color due to the formation of copper sucrose.
The solution is saved for the next experiment.
Experience No. 4 Lack of reducing ability in sucrose
The copper saccharate solution is gently heated to boiling over a burner flame, holding the tube so that only the top of the solution is heated. Sucrose does not oxidize under these conditions, which indicates the absence of a free aldehyde group in its molecule.
Experience No. 5Acid hydrolysis of sucrose
Place 1 drop of sucrose solution, 1 I drop of 2 N. of hydrochloric acid, 3 drops of water and gently heated over a burner flame for 20-30 minutes. Half of the solution is poured into another test tube and 4-5 drops of alkali solution are added to it (up to alkaline reaction per litmus) and 3-4 drops of water. Then add 1 drop of copper sulfate solution and heat upper part blue solution to a boil. An orange-yellow color appears, indicating the formation of glucose. To the rest of the hydrolyzed sucrose solution (first tube) add a crystal of resorcinol, 2 drops of concentrated hydrochloric acid and heat to a boil. a reddish color appears, indicating the formation of fructose. the sucrose molecule is easily split upon hydrolysis into a glucose molecule and a fructose molecule. Both monosaccharides are part of sucrose in cyclic forms. Both glycosidic hydroxyls are involved in creating a bond between them.
In sucrose, the fructose residue is in the form of a fragile five-membered ring - furanose; such complex sugars are very easily hydrolyzed.
Output:
Experience number 6. Acid hydrolysis of starch
IN 7 test tubes are placed in 3 drops of very dilute, almost colorless iodine water. Pour 10 ml of starch paste into a porcelain cup, add 5 ml of sulfuric acid solution and mix the contents with a glass rod. Put the cup with the solution on the asbestos mesh and heat it on a small flame. Every 30 s, 1 drop of the solution is taken with a pipette with a capillary hole and transferred to another test tube with iodine water. Successive samples show a gradual color change upon reaction with iodine. Sample Coloring
First. . Blue
Second. blue purple
Third Red-violet
Fourth ...... Reddish orange
Fifth........ Orange
6th Orange-yellow
Seventh Light yellow (color of iodine water)
The solution is cooled, neutralized with a solution of alkali on red litmus paper to a strongly alkaline reaction, a drop of Fehling's reagent is added and heated. The appearance of an orange color proves that the end product of hydrolysis is glucose.
(FROM 6 H 10 ABOUT 5 ) X + xN 2 0 = xC 6 H 12 0 6
glucose starch
When heated with dilute mineral acids, as well as under the influence of enzymes, starch undergoes hydrolysis. The hydrolysis of starch occurs stepwise with the formation of more and more simple carbohydrates.
The scheme of gradual hydrolysis of starch is as follows:
(FROM 6 H 10 ABOUT 5 ) X → (C 6 H 10 ABOUT 5 )y →(FROM 6 H 10 ABOUT 5 ) z → FROM 12 H 22 0 11 → FROM 6 H 12 ABOUT b
soluble starch dextrins maltose glucose
The first product of hydrolysis - soluble starch - does not form a paste, with iodine it gives a blue color. Upon further hydrolysis, dextrins- simpler polysaccharides, giving color from blue-violet to orange with iodine. Maltose and then glucose do not change the normal color of iodine.
Experience number 7. Cellulose or cellulose
Fiber is the basis of individual organs of all plants, their skeleton. It is built in the same way as starch - from a large number glucose residues. Individual units of glucose are linked in cellulose to each other through beta-glucosidic hydroxyls.
The difference in the interlocking of glucose molecules in starch and fiber leads to a sharp difference in some of their properties. Cellulose dissolves in an ammonia solution of copper oxide hydrate (Schweitzer's reagent). At the same time, its molecules are partially split into smaller fragments. If such a solution is neutralized with acid, then the fiber will again appear in the form of a flocculent mass, but with a slightly changed length and structure of the molecules.
After a short treatment with strong sulfuric acid, the fiber dissolves, forming a sticky mass - amyloid. Amyloid stains blue with iodine. Filter paper after treatment with sulfuric acid becomes more durable and translucent. This is due to the fact that amyloid sticks together individual fibers of cellulose (vegetable parchment)
B. Obtaining vegetable parchment a. Dip a strip of filter paper halfway into a cup of 80% sulfuric acid for 30-40 seconds. Then lower the paper into a vessel with water and finally rinse it in an ammonia solution. Compare the untreated and acid-treated parts of the paper strip (transparency, strength). Be careful when doing this experiment; do not spray sulfuric acid when transferring paper to water!
Write down the results of the experiment.
Control questions on the topic "Properties of polysaccharides"
1. What compounds are called polysaccharides
2. What compounds are called disaccharides?
3. Using the text of the textbook paragraph, prepare written answers to the following questions:
a) What are the physical properties of cellulose?
b) Where is cellulose found in nature? c) What is the formula of the elementary unit of the cellulose macromolecule?
d) what is the main difference between starch, glycogen and fiber?
4. Draw a chart showing the use of starch.
5. List the chemical properties of cellulose.
6. What is called invert sugar?
Lab #12Heterocyclic compounds
Reagents and materials: furfural freshly prepared; silver nitrate, 0.2 n. solution; ammonia, 2 n. solution; fuchsine sulfuric acid; aniline; phloroglucinol; hydrochloric acid (^=1.19 g/cm3); acetic acid glacial. mucic acid; ammonia, concentrated solution; glycerol; hydrochloric acid (ρ = 1.19 g / cm 3). indigo (finely ground powder); sulfuric acid (ρ = 1.84 g / cm 3); tin (II) chloride, 1 N. solution in hydrochloric acid medium; caustic soda, 1 N. solution.
Equipment: pine splinter, glass rod. white cloth; filter paper; water bath; mortar and pestle.
An experienceNo. 1. Furfural reactions
Equipment: watch glass; glass rod; filter paper.
2 drops of furfural, 8 drops of water are placed in a test tube and shaken until complete dissolution of furfural.
Reaction with fuchsine sulfuric acid. 4 drops of fuchsine sulfuric acid, a drop of furfural solution are placed on a watch glass and mixed with a glass rod. After a while, a slightly noticeable pink coloration appears.
Reaction with silver ammonia. Place a drop of silver nitrate and a drop of ammonia solution on a watch glass. A precipitate of silver hydroxide precipitates. Another drop of ammonia is added and a clear solution of the silver complex salt [Ag(]NH3) 2 ]OH is obtained.
A drop of furfural solution is added to the silver ammonia solution. Free silver appears on the glass in the form of a black spot or a silvery coating.
3. reaction with aniline. On a watch glass, a drop of aniline is mixed with a drop of acetic acid. A strip of filter paper is moistened with the resulting solution and a drop of furfural is applied to it. A pink-red spot appears.
4. Reaction with phloroglucinol. Place 3 drops of furfural solution, 1 drop of hydrochloric acid and 2 phloroglucin crystals into a test tube. When heated, the mixture turns dark green. Furfural has the properties of aromatic aldehydes. It easily gives a "silver mirror" reaction, colors fuchsine sulfuric acid, and forms phenylhydrazone.
The color reactions of furfural with aniline and phloroglucinum are based on a condensation reaction. Furfural in the presence of hydrochloric or acetic acid gives colored condensation products with aniline, benzidine, resorcinol, xylidine.
An experienceNo. 2. Getting pyrrole.Qualitative reaction to pyrrole
(An experiencecarry outinfume hoodcloset!)
Several crystals of mucic acid, 2 drops of ammonia solution are placed in a test tube and the contents of the test tube are thoroughly mixed with a glass rod. Add 2 drops of glycerin and stir the mixture again. The test tube is gently heated in the flame of a burner. A pine splinter is moistened with 1 drop of hydrochloric acid and brought into the upper part of the test tube, continuing to heat it. Pyrrole vapors turn the pine torch red.
When ammonia is added, the ammonium salt of mucic acid is obtained, which then decomposes. The breakdown products include pyrrole. Glycerin influences the course of the reaction, making it more uniform. Pyrrole is easily resinified by acids, turning red.
An experienceNo. 3. Properties of indigo
1. Solubility of indigo in water. Indigo powder is placed in a test tube at the tip of a microscapula and 5-6 drops of water are added. The contents of the tube carefully
shaken at room temperature and then heated in a burner flame. One drop of the resulting mixture is applied to a strip of filter paper - a colorless spot is formed, in the center of which blue indigo powder settles. Indigo does not dissolve in water, as in most common solvents.
2 "Cubic" dyeing. Place 5 drops of tin (II) chloride solution in a test tube and add sodium hydroxide solution drop by drop until the formed precipitate dissolves. In a small mortar, carefully grind a few indigo crystals with 5-6 drops of water. Pipette 2 drops of the resulting suspension into a test tube with sodium stannite solution and heat the tube in a boiling water bath until the reaction mixture becomes clear.
In the resulting alkaline solution of white indigo, a small strip of white cloth, pre-stretched and wrung out, is placed. The fabric is carefully soaked in a solution of reduced indigo, then squeezed out and left in the air. The fabric first takes on a green color, and then blue.
Indigo blue is a “vat” dye; in an alkaline environment, indigo blue is reduced to white indigo, which has a phenolic character and is soluble in alkalis. An alkaline solution of white indigo is called a "cube". A fabric is dipped into such a solution, impregnated with a solution and then left in the air for “aging”. On the fibers of the fabric, white indigo is oxidized by atmospheric oxygen into insoluble blue indigo.
indigo blue indigo white
Experience number 4. Oxidation of indigo with a strong oxidizing agent
When indigo is oxidized with a strong oxidizing agent, isatin is obtained, which has a yellow color in solutions (solid isatin is red):
Pour about 1 ml of indigo carmine solution and 5-10 drops of concentrated nitric acid into a test tube. What is observed? How did the color of the solution change?
Write down the result of the experiment
indigo Isatin
Control questions on the topic "Heterocyclic compounds"
1. What compounds are called heterocyclic
2. write the formulas and names of the most important five-membered heterocycles
2. write the formulas and names of the most important six-membered heterocycles
§ 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 excessive content of fats in food. At the same time, in many developing countries On the contrary, there are not enough fats 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. Chemical composition 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 physiochemical properties 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 by glycerol and fatty acids. Fatty acids are the common name for the monobasic aliphatic carboxylic acids RCOOH. Hydrolysis of triacylglycerols produces glycerol and fatty acid:
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. Fatty acids are found in nature a large number double bonds, for example, linoleic (two double bonds), linolenic (three double bonds), arachidonic (four double bonds).
Triacylglycerols are short chain fatty acids or a high degree unsaturation, as a rule, have more low temperatures melting. 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 widespread use of synthetic detergents. 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 new life. "Behold, I make all things new", "Whoever is in Christ, he is a new creation (creation)."
Lipids.
organic matter.
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.
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 with the addition of surfactants.
Experience No. 3. Saponification of fats in a water-alcohol solution of alkali. (Video demo) Short description 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 refrigerate the tube cold water, remove the resulting soap and leave for the following 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.
Highest value monosaccharides are glucose and fructose.
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.
