What does glucose react with under normal conditions. What is glucose? Obtaining glucose and its properties
Carbohydrates are organic substances whose molecules consist of carbon, hydrogen and oxygen atoms. Moreover, hydrogen and oxygen in them are in the same proportions as in water molecules (1: 2)
The general formula of carbohydrates is C n (H 2 O) m, i.e. they seem to consist of carbon and water, hence the name of the class, which has historical roots. It appeared on the basis of the analysis of the first known hydrocarbons. Later it was found that there are carbohydrates in the molecules of which there is no ratio 1H: 2O, for example, deoxyribose - C 5 H 10 O 4 . Organic compounds are also known, the composition of which fits the given general formula, but which do not belong to the class of carbohydrates. These include, for example, formaldehyde CH 2 O and acetic acid CH 3 COOH.
However, the name "hydrocarbons" has taken root and is generally recognized for these substances.
Hydrocarbons according to their ability to hydrolyze can be divided into three main groups: mono-, di- and polysaccharides.
Monosaccharides- carbohydrates that are not hydrolyzed (not decomposed by water). In turn, depending on the number of carbon atoms. Monosaccharides are classified into trioses(whose molecules contain three carbon atoms), tetroses(four atoms), pentoses(five), hexoses(six), etc.
In nature, monosaccharides are predominantly provided pentoses And hexoses. Pentoses include, for example, ribose C 5 H 10 O 5 and deoxyribose(ribose, from which the oxygen atom was “taken away”) C 5 H 10 O 4. They are part of RNA and DNA and determine the first part of the names of nucleic acids.
Hexoses having the general molecular formula C 6 H 12 O 6 include, for example, glucose, fructose, galactose.
disaccharides- carbohydrates that are hydrolyzed to form two molecules of monosaccharides, such as hexoses. The general formula of the vast majority of disaccharides is not difficult to deduce: you need to “add” the two hexose formulas and “subtract” the water molecule from the resulting formula - C 12 H 22 O 10. Accordingly, the general hydrolysis equation can also be written:
C 12 H 22 O 10 + H 2 O → 2C 6 H 12 O 6
Disaccharides include:
1) C sucrose(ordinary food sugar), which, when hydrolyzed, forms one glucose molecule and a fructose molecule. It is found in large quantities in sugar beets, sugar cane (hence the names - beet and cane sugar), maple (Canadian pioneers extracted maple sugar), sugar palm, corn, etc.
2) Maltose(malt sugar), which is hydrolyzed to form two molecules of glucose. Maltose can be obtained by hydrolysis of starch under the action of enzymes contained in malt - germinated, dried and ground barley grains.
3)Lactose(milk sugar), which is hydrolyzed to form glucose and galactose molecules. It is found in the milk of mammals, has a low sweetness, and is used as a filler in pills and pharmaceutical tablets.
The sweet taste of different mono- and disaccharides is different. So, the sweetest monosaccharide - fructose - is 1.5 times sweeter than glucose, which is taken as a standard. . sucrose(disaccharide), in turn, is 2 times sweeter than glucose, and 4-5 times sweeter than lactose, which is almost tasteless.
Polysaccharides - starch, glycogen, dextrins, cellulose, etc. - carbohydrates that are hydrolyzed to form many monosaccharide molecules, most often glucose.
To derive the formula of polysaccharides, it is necessary to “subtract” a water molecule from a glucose molecule and write an expression with the index n: (C 6 H 10 O 5) n. After all, it is precisely due to the elimination of water molecules that di- and polysaccharides are formed in nature.
The role of carbohydrates in nature and their price in human life is extremely important. Formed in plant cells as a result of photosynthesis, they act as a source of energy for animal cells. First of all, this applies to glucose.
Many carbohydrates (starch, glycogen, sucrose) perform a storage function, the role of a reserve of nutrients.
DNA and RNA acids, which include some carbohydrates (pentose-ribose and deoxyribose), perform the functions of transmitting hereditary information.
Cellulose - the building material of plant cells - plays the role of a framework for the membranes of these cells. Another polysaccharide chitin- performs a similar role in the cells of some animals: the outer skeleton of arthropods (crustaceans), insects, and arachnids is formed.
Carbohydrates are the ultimate source of our nutrition, whether we consume starchy grains or feed them to animals that convert starch into fats and proteins. The most hygienic clothes are made from cellulose or products based on it: cotton and linen, viscose fiber, acetate silk. Wooden houses and furniture are built from the same pulp that makes up wood. At the heart of the production of film and photographic film is the same cellulose. Books, newspapers, letters, banknotes - all these are products of the pulp and paper industry. This means that carbohydrates provide us with the most necessary for life: food, clothing, shelter.
In addition, carbohydrates are involved in the construction of complex proteins, enzymes, hormones. Carbohydrates are also such vital substances as heparin (it plays an important role - it prevents blood clotting), agar-agar (it is obtained from seaweed and used in the microbiological and confectionery industries - remember the famous Bird's Milk cake).
It must be emphasized that the only type of energy on Earth (besides nuclear, of course) is the energy of the Sun, and the only way to accumulate it to ensure the vital activity of all living organisms is the process of photosynthesis, which takes place in cells and leads to the synthesis of carbohydrates from water and carbon dioxide. It is during this transformation that oxygen is formed, without which life on our planet would be impossible:
6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2
Physical properties and being in nature
Glucose And fructose- solid and colorless substances crystalline substances. Glucose, found in the juice of grapes (hence the name "grape sugar"), together with fructose, which is found in some fruits and vegetables (hence the name "fruit sugar"), makes up a significant portion of honey. The blood of humans and animals constantly contains about 0.1% glucose (80-120 mg per 100 ml of blood). Its largest part (about 70%) undergoes slow oxidation in the tissues with the release of energy and the formation of end products - water and carbon dioxide (glycolysis process):
C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + 2920 kJ
The energy released during glycolysis largely provides the energy needs of living organisms.
An increase in blood glucose levels of 180 mg per 100 ml indicates a violation of carbohydrate metabolism and the development of a dangerous disease - diabetes mellitus.
The structure of the glucose molecule
The structure of the glucose molecule can be judged on the basis of experimental data. It reacts with carboxylic acids to form esters containing 1 to 5 acid residues. If a glucose solution is added to freshly obtained copper hydroxide (||), then the precipitate dissolves and a bright blue solution of the copper compound is obtained, i.e., a qualitative reaction to polyhydric alcohols occurs. Hence , glucose is a polyhydric alcohol. If the resulting solution is heated, then a precipitate again falls out, then already reddish in color, i.e. there will be a qualitative response to aldehydes. Similarly, if a glucose solution is heated with an ammonia solution of silver oxide, then a “silver mirror” reaction will occur. Therefore, glucose is both a polyhydric alcohol and an aldehyde - aldehyde alcohol. Let's try to derive the structural formula of glucose. There are six carbon atoms in the C 6 H 12 O 6 molecule. One atom is part of the aldehyde group:
The remaining five atoms bind to hydroxyl groups. And finally, given that carbon is tetravalent, let's arrange the hydrogen atoms:
or:
However, it has been established that in addition to linear (aldehyde) molecules in a glucose solution, there are molecules of a cyclic structure that make up crystalline glucose. The transformation of molecules of a linear form into a cyclic one can be explained if we recall that carbon atoms can freely rotate around σ-bonds located at an angle of 109 about 28 / while the aldehyde group (1st carbon atom) can approach the hydroxyl group of the fifth carbon atom. In the first, under the influence of the hydroxy group, the π-bond is broken: a hydrogen atom is attached to the oxygen atom, and the oxygen of the hydroxy group that has "lost" this atom closes the cycle.
As a result of this rearrangement of atoms, a cyclic molecule is formed. The cyclic formula shows not only the order of bonding of atoms, but also their spatial arrangement. As a result of the interaction of the first and fifth carbon atoms, a new hydroxyl group appears at the first atom, which can occupy two positions in space: above and below the cycle plane, and therefore two cyclic forms of glucose are possible:
1) α-form of glucose - hydroxyl groups at the first and second carbon atoms are located on one side of the ring of the molecule;
2) β-forms of glucose - hydroxyl groups are located on opposite sides of the ring of the molecule:
In an aqueous solution of glucose, three of its isomeric forms are in dynamic equilibrium: the cyclic α-form, the linear (aldehyde) form, and the cyclic β-form.
In the established dynamic equilibrium, the β-form predominates (about 63%), since it is energetically preferable - it has OH groups at the first and second carbon atoms on opposite sides of the cycle. In the α-form (about 37%), the OH groups of the same carbon atoms are located on one side of the plane, so it is energetically less stable than the β-form. The share of the linear form in equilibrium is very small (only about 0.0026%).
The dynamic balance can be shifted. For example, when an ammonia solution of silver oxide acts on glucose, the amount of its linear (aldehyde) form, which is very small in solution, is replenished all the time due to cyclic forms, and glucose is completely oxidized to gluconic acid.
An isomer of the aldehyde alcohol of glucose is the keto alcohol fructose.
Chemical properties of glucose
The chemical properties of glucose, like any organic substance, are determined by its structure. Glucose has a dual function, being both an aldehyde and a polyhydric alcohol; therefore, it is characterized by the properties of both polyhydric alcohols and aldehydes.
Reactions of glucose as a polyhydric alcohol
Glucose gives a qualitative reaction of polyhydric alcohols (remember glycerol) with freshly prepared copper hydroxide (ǀǀ), forming a bright blue solution of a copper compound (ǀǀ).
Glucose, like alcohols, can form esters.
Reactions of glucose as an aldehyde
1. Oxidation of the aldehyde group. Glucose, as an aldehyde, is able to oxidize to the corresponding (gluconic) acid and give qualitative reactions to aldehydes. The reaction of the "Silver Mirror" (when heated):
CH 2 -OH-(CHOH) 4 -COH + Ag 2 O → CH 2 OH-(CHOH) 4 -COOH + 2Ag↓
Reaction with freshly obtained Cu (OH) 2 when heated:
CH 2 -OH-(CHOH) 4 -COH + 2 Cu(OH) 2 → CH 2 -OH-(CHOH) 4 -COOH + Cu 2 O↓ + H 2 O
2. Recovery of the aldehyde group. Glucose can be reduced to the corresponding alcohol (sorbitol):
CH 2 -OH-(CHOH) 4 -COH + H 2 → CH 2 -OH-(CHOH) 4 -CH 2 -OH
Fermentation reactions
These reactions proceed under the action of special biological catalysts of protein nature - enzymes.
1.Alcoholic fermentation:
C 6 H 12 O 6 → 2C 2 H 5 OH + 2CO 2
It has long been used by man to produce ethyl alcohol and alcoholic beverages.
2. Lactic fermentation:
which forms the basis of the vital activity of lactic acid bacteria and occurs during the souring of milk, pickling cabbage and cucumbers, ensiling green fodder
Glucose C 6 H 12 O 6- a monosaccharide that is not hydrolyzed to form simpler carbohydrates.
As can be seen from the structural formula, glucose is both a polyhydric alcohol and an aldehyde, that is aldehyde alcohol. In aqueous solutions, glucose can take a cyclic form.
Physical properties
Glucose is a colorless crystalline substance with a sweet taste, highly soluble in water. Less sweet than beet sugar.
1) it is found in almost all plant organs: in fruits, roots, leaves, flowers;
2) especially a lot of glucose in grape juice and ripe fruits, berries;
3) glucose is found in animal organisms;
4) it contains approximately 0.1% in human blood.
Features of the structure of glucose:
1. The composition of glucose is expressed by the formula: C6H12O6, it belongs to polyhydric alcohols.
2. If a solution of this substance is added to freshly precipitated copper (II) hydroxide, a bright blue solution is formed, as in the case of glycerol.
Experience confirms that glucose belongs to polyhydric alcohols.
3. There is an ester of glucose, in the molecule of which there are five residues of acetic acid. From this it follows that there are five hydroxyl groups in the carbohydrate molecule. This fact explains why glucose dissolves well in water and tastes sweet.
If a glucose solution is heated with an ammonia solution of silver oxide (I), then a characteristic "silver mirror" will be obtained.
The sixth oxygen atom in the molecule of the substance is part of the aldehyde group.
4. To get a complete picture of the structure of glucose, you need to know how the skeleton of the molecule is built. Since all six oxygen atoms are part of the functional groups, therefore, the carbon atoms that form the skeleton are directly connected to each other.
5. The chain of carbon atoms is straight, not branched.
6. An aldehyde group can only be at the end of an unbranched carbon chain, and hydroxyl groups can be stable only at different carbon atoms.
Chemical properties
Glucose has chemical properties characteristic of alcohols and aldehydes. In addition, it also has some specific properties.
1. Glucose is a polyhydric alcohol.
Glucose with Cu (OH) 2 gives a blue solution (copper gluconate)
2. Glucose - aldehyde.
a) Reacts with an ammonia solution of silver oxide to form a silver mirror:
CH 2 OH-(CHOH) 4 -CHO + Ag 2 O → CH 2 OH-(CHOH) 4 -COOH + 2Ag
gluconic acid
b) With copper hydroxide gives a red precipitate Cu 2 O
CH 2 OH-(CHOH) 4 -CHO + 2Cu(OH) 2 → CH 2 OH-(CHOH) 4 -COOH + Cu 2 O↓ + 2H 2 O
gluconic acid
c) It is reduced by hydrogen to form a six-hydric alcohol (sorbitol)
CH 2 OH-(CHOH) 4 -CHO + H 2 → CH 2 OH-(CHOH) 4 -CH 2 OH
3. Fermentation
a) Alcoholic fermentation (to obtain alcoholic beverages)
C 6 H 12 O 6 → 2CH 3 -CH 2 OH + 2CO 2
ethanol
b) Lactic acid fermentation (souring of milk, fermentation of vegetables)
C 6 H 12 O 6 → 2CH 3 -CHOH-COOH
lactic acid
Application, meaning
Glucose is produced in plants during photosynthesis. Animals get it from food. Glucose is the main source of energy in living organisms. Glucose is a valuable nutritious product. It is used in confectionery, in medicine as a tonic, for the production of alcohol, vitamin C, etc.
Glucose (dextrose) is a monosaccharide that is a universal source of energy for humans. It is the end product of the hydrolysis of di- and polysaccharides. The compound was discovered by the English physician William Prout in 1802.
Glucose or grape sugar is an essential nutrient for the human central nervous system. It ensures the normal functioning of the body with strong physical, emotional, intellectual stress and a quick response of the brain to force majeure situations. In other words, glucose is a jet fuel that supports all life processes at the cellular level.
The structural formula of the compound is C6H12O6.
Glucose is a crystalline substance of sweet taste, odorless, highly soluble in water, concentrated solutions of sulfuric acid, zinc chloride, Schweitzer's reagent. In nature, it is formed as a result of plant photosynthesis, in industry - by hydrolysis of cellulose,.
The molar mass of the compound is 180.16 grams per mole.
The sweetness of glucose is half that of sucrose.
Used in cooking, medical industry. Preparations based on it are used to relieve intoxication and determine the presence, type of diabetes mellitus.
Consider hyperglycemia / hypoglycemia - what it is, the benefits and harms of glucose, where it is contained, and its use in medicine.
Daily rate
To nourish brain cells, red blood cells, striated muscles and provide the body with energy, a person needs to eat “his” individual norm. To calculate it, multiply the actual body weight by a factor of 2.6. The resulting value is the daily requirement of your body for a monosaccharide.
At the same time, knowledge workers (office employees) performing computational planning operations, athletes and people experiencing heavy physical exertion should increase the daily norm. Since these operations require more energy expended.
The need for glucose decreases with a sedentary lifestyle, a tendency to diabetes, and overweight. In this case, for energy production, the body will use not easily digestible saccharide, but fat reserves.
Remember, glucose in moderate doses is a medicine and “fuel” for internal organs and systems. At the same time, excessive consumption of sweetness turns it into poison, turning beneficial properties into harm.
Hyperglycemia and hypoglycemia
In a healthy person, the fasting blood glucose level is 3.3 - 5.5 millimoles per liter, after eating it rises to 7.8.
If this indicator is below the norm, hypoglycemia develops, if it is higher, hyperglycemia develops. Any deviation from the permissible value causes disturbances in the body, often irreversible disorders.
Elevated blood glucose increases the production of insulin, which leads to intensive work of the pancreas "for wear and tear." As a result, the body begins to deplete, there is a risk of developing diabetes, immunity suffers. When the concentration of glucose in the blood reaches 10 millimoles per liter, the liver ceases to cope with its functions, the work of the circulatory system is disrupted. An excess of sugar is converted into triglycerides (fat cells), which provoke the appearance of coronary disease, atherosclerosis, hypertension, heart attack, cerebral hemorrhage.
The main reason for the development of hyperglycemia is a violation of the functioning of the pancreas.
Foods that lower blood sugar:
- oatmeal;
- lobsters, lobsters, crabs;
- blueberry juice;
- tomatoes, Jerusalem artichoke, blackcurrant;
- soy cheese;
- lettuce leaves, pumpkin;
- green tea;
- avocado;
- meat, fish, chicken;
- lemon, grapefruit;
- almonds, cashews, peanuts;
- legumes;
- watermelon;
- garlic and onion.
A drop in blood glucose leads to malnutrition of the brain, a weakening of the body, which sooner or later leads to fainting. A person loses strength, muscle weakness, apathy appears, physical activity is difficult, coordination deteriorates, there is a feeling of anxiety, clouding of consciousness. Cells are in a state of starvation, their division and regeneration slows down, and the risk of tissue death increases.
Causes of hypoglycemia: alcohol poisoning, lack of sugary foods in the diet, cancer, thyroid dysfunction.
To maintain blood glucose within normal limits, pay attention to the work of the insular apparatus, enrich the daily menu with healthy natural sweets containing monosaccharide. Remember, a low level of insulin prevents the full absorption of the compound, as a result, hypoglycemia develops. At the same time, adrenaline, on the contrary, will help to increase it.
Benefit and harm
The main functions of glucose are nutritional and energy. Thanks to them, it supports the heartbeat, breathing, muscle contraction, brain function, nervous system and regulates body temperature.
The value of glucose in the human body:
- Participates in metabolic processes, acts as the most digestible energy resource.
- Supports the body's performance.
- Nourishes brain cells, improves memory, learning.
- Stimulates the work of the heart.
- Quickly satisfies the feeling of hunger.
- Relieves stress, corrects mental state.
- Accelerates the recovery of muscle tissue.
- Helps the liver to neutralize toxic substances.
How many years have glucose been used to intoxicate the body, with hypoglycemia. Monosaccharide is part of blood substitutes, anti-shock drugs used to treat diseases of the liver and central nervous system.
In addition to the positive effect, glucose can harm the body of people in old age, patients with impaired metabolism and lead to the following consequences:
- obesity
- the development of thrombophlebitis;
- overload of the pancreas;
- the occurrence of allergic reactions;
- an increase in cholesterol;
- the appearance of inflammatory, heart diseases, coronary circulation disorder;
- arterial hypertension;
- damage to the retina;
- endothelial dysfunction.
Remember, the delivery of a monosaccharide to the body must be fully compensated by the consumption of calories for energy needs.
Sources
The monosaccharide is found in animal muscle glycogen, starch, berries and fruits. 50% of the energy needed for the body, a person receives from glycogen (deposited in the liver, muscle tissue) and the use of glucose-containing foods.
The main natural source of the compound is honey (80%), it also contains another useful carbohydrate - fructose.
| Product name | Monosaccharide content in 100 grams, grams |
|---|---|
| Rafinated sugar | 99,7 |
| Bee Honey | 80,1 |
| Marmalade | 79,2 |
| Gingerbread | 77,6 |
| Pasta | 70,5 |
| sweet straw | 69,1 |
| Dates | 69,0 |
| Pearl barley | 66,8 |
| Dried apricots | 66,1 |
| Raisin | 65,6 |
| apple jam | 65,0 |
| Chocolate | 63,2 |
| Rice | 62,2 |
| Oatmeal | 61,7 |
| Corn | 61,3 |
| Buckwheat | 60,3 |
| White bread | 52,8 |
| Rye bread | 44,2 |
| Ice cream | 21,2 |
| Potato | 8,0 |
| Apples | 7,8 |
| Grape | 7,7 |
| Beet | 6,6 |
| Carrot | 5,6 |
| Cherry | 5,4 |
| Cherries | 5,4 |
| Milk | 4,4 |
| Gooseberry | 4,3 |
| Pumpkin | 4,1 |
| Legumes | 4,1 |
| Cabbage | 4,0 |
| Raspberries | 3,8 |
| Tomatoes | 3,3 |
| Cottage cheese | 3,2 |
| Sour cream | 3,0 |
| plums | 3,0 |
| Liver | 2,7 |
| Strawberry | 2,6 |
| Cranberry | 2,4 |
| Watermelon | 2,3 |
| oranges | 2,3 |
| 2,1 | |
| tangerines | 2,0 |
| Cheese | 2,0 |
| Peaches | 2,0 |
| Pear | 1,7 |
| Black currant | 1,4 |
| cucumbers | 1,2 |
| Oil | 0,4 |
| Eggs | 0,3 |
Glucose in medicine: release form
Glucose preparations are classified as detoxification and metabolic agents. Their spectrum of action is aimed at improving metabolic and redox processes in the body. The active substance of these medicines is dextrose monohydrate (sublimated glucose in combination with excipients).
Forms of release and pharmacological properties of the monosaccharide:
- Tablets containing 0.5 grams of dry dextrose. When taken orally, glucose has a vasodilating and sedative effect (moderately pronounced). In addition, the drug replenishes energy reserves, increasing intellectual and physical productivity.
- Solution for infusion. In a liter of 5% glucose, there are 50 grams of anhydrous dextrose, in a 10% composition - 100 grams of the substance, in a 20% mixture - 200 grams, in a 40% concentrate - 400 grams of saccharide. Given that a 5% saccharide solution is isotonic with respect to blood plasma, the introduction of the drug into the bloodstream helps to normalize the acid-base and water-electrolyte balance in the body.
- Solution for intravenous injection. A milliliter of 5% concentrate contains 50 milligrams of dried dextrose, 10% contains 100 milligrams, 25% contains 250 milligrams, and 40% contains 400 milligrams. When administered intravenously, glucose increases osmotic blood pressure, dilates blood vessels, increases urination, enhances the outflow of fluid from tissues, activates metabolic processes in the liver, and normalizes myocardial contractile function.
In addition, the saccharide is used for artificial therapeutic nutrition, including enteral and parenteral.
In what cases and in what dosage is "medical" glucose prescribed?
Indications for use:
- hypoglycemia (low blood sugar);
- lack of carbohydrate nutrition (with mental and physical overload);
- rehabilitation period after protracted diseases, including infectious ones (as additional nutrition);
- decompensation of cardiac activity, intestinal infectious pathologies, liver diseases, hemorrhagic diathesis (in complex therapy);
- collapse (sudden drop in blood pressure);
- dehydration caused by vomiting, diarrhea, or surgery;
- intoxication or poisoning (including drugs, arsenic, acids, carbon monoxide, phosgene);
- to increase the size of the fetus during pregnancy (in case of suspected low weight).
In addition, "liquid" glucose is used to dilute drugs administered parenterally.
Isotonic glucose solution (5%) is administered in the following ways:
- subcutaneously (single serving - 300 - 500 milliliters);
- intravenous drip (maximum injection rate - 400 milliliters per hour, daily rate for adults - 500 - 3000 milliliters, daily dose for children - 100 - 170 milliliters of solution per kilogram of the child's weight, for newborns this figure is reduced to 60);
- in the form of enemas (a single portion of the substance varies from 300 to 2000 milliliters, depending on the age and condition of the patient).
Hypertonic glucose concentrates (10%, 25% and 40%) are used only for intravenous injections. And at one time, no more than 20 - 50 milliliters of the solution are injected. However, with large blood loss, hypoglycemia, hypertonic fluid is used for infusion infusions (100 - 300 milliliters per day).
Remember, the pharmacological properties of glucose enhance (1%), insulin, methylene blue (1%).
Glucose tablets are taken orally, 1 to 2 pieces per day (if necessary, increase the daily dose to 10 tablets).
Contraindications to taking glucose:
- diabetes;
- pathologies accompanied by an increase in the concentration of sugar in the blood;
- individual glucose intolerance.
Side effects:
- hyperhydration (due to the introduction of volumetric portions of isotonic solution);
- loss of appetite;
- necrosis of the subcutaneous tissue (when a hypertonic solution gets under the skin);
- acute heart failure;
- inflammation of the veins, thrombosis (due to the rapid introduction of the solution);
- dysfunction of the insular apparatus.
Remember, too rapid administration of glucose is fraught with hyperglycemia, osmotic diuresis, hypervolemia, hyperglucosuria.
Conclusion
Glucose is an important nutrient for the human body.
Monosaccharide intake should be reasonable. Excessive or insufficient intake undermines the immune system, disrupts metabolism, causes health problems (leads to an imbalance in the work of the heart, endocrine, nervous systems, reduces brain activity).
In order for the body to be at a high level of efficiency and get enough energy, avoid exhausting physical exertion, stress, monitor the functioning of the liver, pancreas, eat healthy carbohydrates (cereals, fruits, vegetables, dried fruits, honey). At the same time, refuse to take "empty" calories, represented by cakes, pastries, sweets, cookies, waffles.
Good day, dear tenth graders!
We are beginning to get acquainted with a new group of organic compounds - carbohydrates.
Carbohydrates ... And these are the very sweets that you love so much (fruits, cakes, sweets, jam, chocolate, etc., especially grapes contain a lot of carbohydrates). Carbohydrates are vital substances that every body needs. These substances are consumed, and a person must constantly replenish their reserves. It is clear that the substances that make up the tissues of the body are not similar to those that it eats. The human body processes food products and in the course of its life constantly consumes energy, which, as we know, is released during oxidation in the tissues of the body, carbohydrates are part of the nucleic acids that carry out protein biosynthesis and the transmission of hereditary traits.
Animals and humans do not synthesize carbohydrates. In green plants, with the participation of chlorophyll and sunlight, a number of processes of converting carbon dioxide absorbed from the air and water absorbed from the soil are carried out. The end product of this process, photosynthesis, is a complex carbohydrate molecule.
Carbohydrates are an important source of energy for the body, they are involved in metabolism. The main sources of carbohydrates are plant foods.
Physiologists have found that with physical activity, which is 10 times higher than usual, a person who follows a fat diet loses strength in half an hour. But a carbohydrate diet allows you to withstand the same load for four hours. It turns out that getting the body of energy from fat is a long process. This is due to the low reactivity of fats, especially their hydrocarbon chains. Carbohydrates, although they provide less energy than fats, however, release it much faster. Therefore, if a thorough load is ahead, it is preferable to eat sweet rather than fatty.
Classification of carbohydrates.
Carbohydrates are an extensive class of natural compounds.Let's turn to scheme 1. "Classification of carbohydrates." Depending on the number of monosaccharide residues in a molecule, they are divided into monosaccharides, disaccharides and polysaccharides.
Monosaccharides (simple carbohydrates) - carbohydrates that are not hydrolyzed. Depending on the number of carbon atoms, they are divided into trioses, tetroses, pentoses, hexoses. The most important for a person glucose, fructose, galactose, ribose, deoxyribose.
Disaccharides - carbohydrates that are hydrolyzed to form two molecules of monosaccharides.
most important to humans sucrose, maltose and lactose.Polysaccharides - macromolecular compounds - carbohydrates that are hydrolyzed to form many molecules of monosaccharides. They are divided into digestible and indigestible in the gastrointestinal tract. The digestible are starch and glycogen, of the second are important for a person cellulose, hemicellulose and pectins.
Carbohydrates often call sugary substances or sugars. They can be tasteless, sweet and bitter. If the sweetness of a sucrose solution is taken as 100%, then the sweetness of fructose is 173%, glucose - 81%, maltose and galactose - 32%, lactose - 16%.
Qualitative composition of carbohydrates.
Carbohydrates- organic compounds consisting of carbon, hydrogen and oxygen, and hydrogen and oxygen are in the ratio (2: 1) as in water, hence the name.
Based on this analogy, the Russian chemist K. Schmidt in 1844 proposed the term carbohydrate (carbon and water), and the general formula for carbohydratesCn(H 2 O) m
So, the most important representative of monosaccharides is glucose. When studying some of the topics we met with you with this substance in the course of chemistry and biology: chemistry - aldehydes, alcohols; biology - photosynthesis, cell structure.
Getting glucose.
1. Photosynthesis reaction.6CO 2 + 6H 2 O –> C 6 H 12 O 6 + 6O 2 + Q
2. Polymerization reaction.
3. Hydrolysis of starch.
(C 6 H 10 O 5) n + nH 2 O –> nC 6 H 12 O 6
Physical properties:
colorless crystalline substance, soluble in water, sweet taste, melting point 146 about C .
The structure of the glucose molecule. Isomerism.
Conclusion: thus, glucose is an aldehyde alcohol, more precisely, a polyhydric aldehyde alcohol.
It has been established that not only its aldehyde form is found in a glucose solution; but also molecules of a cyclic structure.
It has been established that at the third carbon atom the group - OH is located differently than at other carbon atoms, the common structure of glucose looks like this:
The transformation of a linear molecule into a cyclic molecule is understandable if we remember that carbon atoms can rotate around sigma bonds. The aldehyde group can approach the hydroxyl group of the 5th carbon atom, since the oxygen atom of the carbonyl group carries a partial - charge, and the hydrogen atom of the hydroxyl group carries a partial + charge.
A peculiar chemical process is carried out: a rupture of the carbonyl group bond occurs, a hydrogen atom joins the oxygen atom, and the oxygen atom of the hydroxyl group closes the chain with the carbon atom. Cyclic forms are in balance, turning into alpha and beta form. Thus, in an aqueous solution of glucose are three isomeric forms. The crystalline glucose molecule has an alpha form, when dissolved in water, an open form, and then again a cyclic beta form. Such isomerism called dynamic (tautomerism).
Chemical properties of glucose.
Monosaccharides enter into chemical reactions characteristic of carbonyl and hydroxyl groups.
1) Silver mirror reaction
You can prove the presence of an aldehyde group in glucose using an ammonia solution of silver oxide. This reaction is called the silver mirror reaction. It is used as quality for opening aldehydes
. The aldehyde group of glucose is oxidized to a carboxyl group. Glucose is converted to gluconic acid.
CH 2 OH - (CHOH) 4 - COOH + Ag 2 O \u003d CH 2 OH - (CHOH) 4 - COOH + 2Ag
(The reaction of a silver mirror is used in industry for silvering mirrors, making flasks for thermoses, Christmas tree decorations).
2) Interaction of glucose with copper (II) hydroxide
3) Hydrogenation of glucose
The aldehyde group can be reduced to a hydroxyl group by the action of hydrogen in the presence of a catalyst.
4) Specific properties. Of great importance are the processes of glucose fermentation occurring under the action of organic enzyme catalysts (they are produced by microorganisms).
a) alcoholic fermentation (by the action of yeast)
C 6 H 12 O 6 = 2C 2 H 5 OH + 2CO 2
b) lactic acid fermentation (under the action of lactic acid bacteria)in the confectionery industry in the manufacture of soft sweets, dessert chocolates, cakes and various dietary products;
- in baking, glucose improves fermentation conditions, gives porosity and good taste to products, slows down hardening;
- in the production of ice cream, it lowers the freezing point, increases its hardness;
- in the production of fruit preserves, juices, liqueurs, wines, soft drinks, since glucose does not mask the aroma and taste;
- in the dairy industry, in the manufacture of dairy products and baby food, it is recommended to use glucose in a certain proportion with sucrose to give these products a higher nutritional value;
- in veterinary medicine;
- in poultry farming;
- in the pharmaceutical industry.
It is advisable to use crystalline glucose for the nutrition of the sick, injured, convalescents, as well as people working with large overloads.
medical glucose used in antibiotics and other drugs, including for intravenous infusions, and for the production of vitamin C. Technical glucose is used as a reducing agent in the leather industry, in textile - in the production of viscose, as a nutrient medium in the cultivation of various types of microorganisms in medical And microbiological industry .
Fixing:
The chemical properties of monosaccharides are due to the peculiarities of their structure.
Consider the chemical properties of glucose as an example.
Monosaccharides exhibit the properties of alcohols and carbonyl compounds.
I. Reactions at the carbonyl group
1. Oxidation.
a) As with all aldehydes, the oxidation of monosaccharides leads to the corresponding acids. So, when glucose is oxidized with an ammonia solution of silver hydroxide, gluconic acid is formed (the "silver mirror" reaction).
Salt of gluconic acid - calcium gluconate - a well-known drug.
b) The reaction of monosaccharides with copper hydroxide when heated also leads to aldonic acids.
blue brick red
These reactions are qualitative for glucose as an aldehyde.
c) Stronger oxidizing agents oxidize not only the aldehyde group, but also the primary alcohol group into the carboxyl group, leading to dibasic sugar (aldaric) acids. Typically, concentrated nitric acid is used for this oxidation.
2. Recovery.
The reduction of sugars leads to polyhydric alcohols. Hydrogen in the presence of nickel, lithium aluminum hydride, etc. are used as a reducing agent.
3. Despite the similarity of the chemical properties of monosaccharides with aldehydes, glucose does not react with sodium hydrosulfite (NaHSO 3).
II. Reactions on hydroxyl groups
Reactions on the hydroxyl groups of monosaccharides are carried out, as a rule, in the hemiacetal (cyclic) form.
1. Alkylation (formation of ethers).
Under the action of methyl alcohol in the presence of gaseous hydrogen chloride, the hydrogen atom of the glycosidic hydroxyl is replaced by a methyl group.
When using stronger alkylating agents, such as, for example, methyl iodide or dimethyl sulfate, such a transformation affects all the hydroxyl groups of the monosaccharide.
2. Acylation (formation of esters).
When acetic anhydride acts on glucose, an ester is formed - pentaacetylglucose.
3. Like all polyhydric alcohols, glucose with copper (II) hydroxide in the cold with the formation of copper (II) gluconate, it gives an intense blue color - a qualitative reaction for glucose as a polyhydric alcohol.
bright blue solution
III. Specific reactions
1. Combustion (as well as complete oxidation in a living organism):
C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O
2. Fermentation reactions
In addition to the above, glucose is also characterized by some specific properties - fermentation processes. Fermentation is the breakdown of sugar molecules under the influence of enzymes (enzymes). Sugars with a multiple of three carbon atoms are fermented. There are many types of fermentation, among which the most famous are the following:
a) alcoholic fermentation
C 6 H 12 O 6 → 2CH 3 -CH 2 OH (ethyl alcohol) + 2CO 2
b) lactic acid fermentation
c) butyric fermentation
C 6 H 12 O 6 → CH 3 -CH 2 -CH 2 -COOH (butyric acid) + 2H 2 + 2CO 2
The mentioned types of fermentation caused by microorganisms are of wide practical importance. For example, alcohol - for the production of ethyl alcohol, in winemaking, brewing, etc., and lactic acid - for the production of lactic acid and fermented milk products.
Fructose enters into all reactions characteristic of polyhydric alcohols, however, the reactions of the aldehyde group, unlike glucose, are not characteristic of it.
Chemical properties ribose C 5 H 10 O 5 similar to glucose.
D) The biological role of glucose.
D-glucose (grape sugar) is widely distributed in nature: found in grapes and other fruits, in honey. It is an essential component of the blood and tissues of animals and a direct source of energy for cellular reactions. The level of glucose in human blood is constant and is in the range of 0.08-0.11%. The entire blood volume of an adult contains 5-6 g of glucose. This amount is sufficient to cover the body's energy costs for 15 minutes. his life activity. In some pathologies, for example, with diabetes mellitus, the blood glucose level rises, and its excess is excreted in the urine. At the same time, the amount of glucose in the urine can increase up to 12% against the usual 0.1%.
3. Disaccharides.
Oligosaccharides are carbohydrates whose molecules contain from 2 to 8-10 monosaccharide residues connected by glycosidic bonds. In accordance with this, disaccharides, trisaccharides, etc. are distinguished.
Disaccharides are complex sugars, each molecule of which, upon hydrolysis, breaks down into two molecules of monosaccharides. Disaccharides, along with polysaccharides, are one of the main sources of carbohydrates in human and animal food. By their structure, disaccharides are glycosides, in which two monosaccharide molecules are connected by a glycosidic bond.
Structure
1. Disaccharide molecules may contain two residues of one monosaccharide or two residues of different monosaccharides;
2. The bonds formed between monosaccharide residues can be of two types:
a) hemiacetal hydroxyls of both monosaccharide molecules take part in the bond formation. For example, the formation of a sucrose molecule;
b) the hemiacetal hydroxyl of one monosaccharide and the alcohol hydroxyl of another monosaccharide take part in the formation of the bond. For example, the formation of molecules of maltose, lactose and cellobiose.
To establish the structure of disaccharides, it is necessary to know: from which monosaccharides it is built, what is the configuration of the anomeric centers of these monosaccharides (- or -), what are the ring sizes (furanose or pyranose), and which hydroxyls are involved in two monosaccharide molecules.
Disaccharides are divided into two groups: reducing and non-reducing.
Among the disaccharides, maltose, lactose and sucrose are particularly well known.
Maltose (malt sugar), which is α-glucopyranosyl-(1-4)-α-glucopyranose, is formed as an intermediate by the action of amylases on starch (or glycogen), contains two α-D-glucose residues. The name of the sugar whose hemiacetal hydroxyl participates in the formation of a glycosidic bond ends in "silt".
In the maltose molecule, the second glucose residue has a free hemiacetal hydroxyl. Such disaccharides have reducing properties.
Reducing disaccharides include, in particular, maltose (malt sugar) contained in malt, i. germinated, and then dried and crushed grains of cereals.
(maltose)
Maltose is composed of two D-glucopyranose residues linked by a (1–4)-glycosidic bond, i.e. the glycosidic hydroxyl of one molecule and the alcohol hydroxyl at the fourth carbon atom of another monosaccharide molecule participate in the formation of an ether bond. The anomeric carbon atom (С 1) involved in the formation of this bond has a -configuration, and the anomeric atom with a free glycosidic hydroxyl (indicated in red) can have both α- (α-maltose) and β-configuration (β- maltose).
Maltose is a white crystal, highly soluble in water, sweet in taste, but much less than that of sugar (sucrose).
As can be seen, maltose contains a free glycosidic hydroxyl, as a result of which the ability to open the ring and transfer to the aldehyde form is retained. In this regard, maltose is able to enter into reactions characteristic of aldehydes, and, in particular, to give the "silver mirror" reaction, therefore it is called a reducing disaccharide. In addition, maltose enters into many reactions characteristic of monosaccharides, for example, it forms ethers and esters.
The disaccharide lactose (milk sugar) is found only in milk and consists of D-galactose and D-glucose. This is α-glucopyranosyl-(1-4)-glucopyranose:
Since the lactose molecule contains a free hemiacetal hydroxyl (in the glucose residue), it belongs to the number of reducing disaccharides.
One of the most common disaccharides is sucrose (cane or beet sugar), a common food sugar. The sucrose molecule consists of one D-glucose and one D-fructose residue. Therefore, it is α-glucopyranosyl-(1-2)-β-fructofuranoside:
Unlike most disaccharides, sucrose does not have a free hemiacetal hydroxyl and does not have reducing properties.
Sucrose (beet or cane sugar) is a non-reducing disaccharide. It is found in sugar cane, sugar beets (up to 28% of dry matter), plant juices and fruits. The sucrose molecule is built from α,D-glucopyranose and β,D-fructofuranose.
(sucrose)
In contrast to maltose, the glycosidic bond (1–2) between monosaccharides is formed due to the glycosidic hydroxyls of both molecules, that is, there is no free glycosidic hydroxyl. As a result, there is no reducing ability of sucrose, it does not give the "silver mirror" reaction, therefore it is referred to as non-reducing disaccharides.
Among natural trisaccharides, few are important. The best known is raffinose, which contains residues of fructose, glucose and galactose, which is found in large quantities in sugar beet and in many other plants.
In general, the oligosaccharides present in plant tissues are more diverse in their composition than the oligosaccharides of animal tissues.
All of them have the same empirical formula C 12 H 22 O 11, i.e. are isomers.
Sucrose is a white crystalline substance, sweet in taste, highly soluble in water.
Sucrose is characterized by reactions on hydroxyl groups. Like all disaccharides, sucrose is converted by acidic or enzymatic hydrolysis into the monosaccharides of which it is composed.
Disaccharides are typical sugar-like carbohydrates; These are solid colorless crystalline substances, very soluble in water, having a sweet taste.
Of the disaccharides, sucrose C 12 H 22 O 11 is of the greatest importance:
The sucrose molecule consists of residues of glucose and fructose molecules.