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The biological role of glucose in the body. What is glucose? Obtaining glucose and its properties

The biological role of glucose in the body. What is glucose? Obtaining glucose and its properties

15.10.2019

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.

Do you know what glucose is? Surely every reader has an idea about this. But can it be argued that we know all the properties and features of glucose? The article will be devoted to the consideration of this substance from a medical point of view.

Introduction

The second name for glucose is dextrose or grape sugar, as the people say. This monosaccharide is one of the main sources of energy for humans. It was scientifically discovered only in 1802 by the physician William Prout.

The main reason for the development of such a disease lies in the disruption of the pancreas. In order to protect yourself from illness, you should eat foods that lower sugar levels: oatmeal, seafood, blueberry juice, black currants, tomatoes, soy cheese, green tea, meat, fish, lemons, grapefruits, almonds, peanuts , Watermelon, Garlic And Onion.

hypoglycemia

When there is little monosaccharide in the blood, the body also suffers. After all, what is glucose? It is a necessary substance for the body, like air for the lungs. When it is not enough, the body weakens, the nutrition of the brain deteriorates, and the person increasingly faints. Other symptoms also include fatigue, muscle weakness, poor coordination. The cells of the body do not receive proper nutrition, their division slows down, as does the regeneration process, which can lead to their complete death.

There are several main causes of hypoglycemia. This is a lack of sweets in the diet, cancer, alcohol poisoning, thyroid dysfunction.

In order to get rid of this disease or carry out prevention, you should review your diet. It is necessary to add to it products that contain glucose in its natural form.

Benefit

To have a complete picture of what glucose is, it is necessary to consider its main functions - nutrition and energy saturation of the body. It is this monosaccharide that supports the functioning of the respiratory system, muscle contraction, heartbeat, and the functioning of the nervous system. What role does glucose play?

It contributes to the activation of metabolic processes, and in itself is easily digestible.
Provides functionality.
Improves memory, learning abilities, nourishes brain cells.
Stimulates cardiac activity.
Promotes the rapid saturation of the body with food.
Affects the normal activity of the nervous system.
Allows faster recovery of muscle tissue.
Accelerates the neutralization of toxic substances in the liver.

In addition, glucose is used as an ingredient in anti-shock drugs, blood substitutes.

Harm

However, in older people, glucose can be very harmful. This is especially true for people who have metabolic disorders. For example, the following complications may occur:

a sharp weight gain;
thrombophlebitis;
violation of the pancreas;
increased cholesterol levels;
allergic reactions;
inflammatory and heart diseases;
arterial hypertension.

Getting energy from glucose should be fully compensated by the energy costs of the processes in the body.

Sources

We learned almost everything there was to know about glucose. The rate of its consumption for each is determined individually. Where to find the required amount of natural monosaccharide? A lot of this substance is found in the muscle tissues of animals, berries, starch and fruits. The richest natural source of glucose is honey, which contains 80% of this monosaccharide. In addition, it contains fructose, which is no less useful for humans. Doctors and nutritionists agree that you should eat foods that will stimulate the body to produce natural saccharides, and not revel in refined sugar and confectionery. It is quite obvious which glucose will be more beneficial for the body. Below is a list of recommended foods to eat:

marmalade;
gingerbread;
dates;
barley porridge;
dried apricots;
raisin;
jam from apples;
apricots.

medical application

The level of glucose in the body can be changed not only by reviewing your diet. Sometimes drugs are used. At the same time, the use of glucose during pregnancy in the form of tablets is highly undesirable. It is worth taking drugs only if the doctor has allowed it. Self-medication can lead to negative consequences. However, a monosaccharide is often prescribed to pregnant women if there is suspicion of a low fetal weight.

In medicine, the spectrum of action of this substance is large. It improves metabolism and promotes redox processes. The active substance of the drug is dextrose monohydrate, that is, glucose known to us with an admixture of other substances.

Just what the doctor ordered

Glucose reactions, which occur automatically in a healthy person, sometimes need to be artificially induced in sick people. Monosaccharide-based drugs are prescribed in such cases:

hypoglycemia;
the need for carbohydrate nutrition;
recovery period after severe and prolonged illness;
intestinal infections and liver diseases;
a sharp drop in blood pressure;
experienced shock;
dehydration of the body;
severe intoxication.

Doctors also use liquid glucose for parenteral administration. This is done in several ways:

subcutaneously;
intravenously;
enema.

Now we know what glucose is, how important it is for health, and what foods you need to add to your diet so that the body has enough nutrients. Remember that deviations from the norm are always bad. It is better to stick to the golden mean in the consumption of sweets of natural and artificial origin.

is a natural dextrose found in berries and fruits. The main content of this substance can be found in grape juice, which is why the substance got its second name - sweet grape sugar.

Glucose is found in large quantities in fruits and berries.

Glucose is monosaccharides with hexose. The composition includes starch, glycogen, cellulose, lactose, sucrose and maltose. Getting into, grape sugar is also split into fructose.

The crystallized substance is colorless, but with a pronounced sweet taste. Glucose is able to dissolve in water, especially in zinc chloride and sulfuric acid.

This allows you to create medicines based on grape sugar to make up for its deficiency. Compared to fructose and sucrose, this monosaccharide is less sweet.

Significance in the life of animals and humans

Why is glucose so important in the body and why is it needed? In nature, this chemical is involved in the process of photosynthesis.

This is because glucose is able to bind and transport energy to cells. In the body of living beings, glucose, due to the energy produced, plays an important role in metabolic processes. Main benefits of glucose:

Grape sugar is an energy fuel, thanks to which cells are able to function smoothly.
In 70%, glucose enters the human body through complex carbohydrates, which, when they get into, break down fructose, galactose and dextrose. The rest of the body produces this chemical, using its own stored reserves.
Glucose penetrates into the cell, saturates it with energy, due to which intracellular reactions develop. Metabolic oxidation and biochemical reactions take place.

Many cells in the body are capable of producing grape sugar on their own, but not the brain. An important organ cannot synthesize glucose, therefore it receives nutrition directly through the blood.

The norm of glucose in the blood, for the normal functioning of the brain, should not be lower than 3.0 mmol / l.

Surplus and deficiency

Overeating can cause excess glucose.

Glucose is not absorbed without insulin, a hormone that is produced in.

If there is a deficiency of insulin in the body, then glucose is not able to penetrate into the cells. It remains unprocessed in human blood and is enclosed in an eternal cycle.

As a rule, with a lack of grape sugar, the cells weaken, starve and die. This relationship is studied in detail in medicine. Now this condition is classified as a serious disease and is called it.

In the absence of insulin and glucose, not all cells die, but only those that are not able to independently absorb the monosaccharide. There are also insulin-independent cells. Glucose in them is absorbed without insulin.

These include brain tissue, muscles, red blood cells. The nutrition of these cells is carried out at the expense of incoming carbohydrates. It can be seen that during starvation or poor nutrition, mental abilities change significantly in a person, weakness, anemia (anemia) appear.

According to statistics, glucose deficiency occurs in only 20%, the remaining percentage is accounted for by an excess of the hormone and monosaccharide. This phenomenon is directly related to overeating. The body is not able to break down carbohydrates that come in large quantities, which is why it simply begins to store glucose and other monosaccharides.

If glucose is stored in the body for a long time, it will be converted into glycogen, which is stored in the muscles. In this situation, the body falls into a stressful state, when glucose becomes excessive.

Since the body cannot independently remove a large amount of grape sugar, it simply deposits it in adipose tissue, due to which a person is rapidly gaining excess weight. This whole process requires a lot of energy (breakdown, conversion of glucose, deposition), so there is a constant feeling of hunger and a person consumes carbohydrates 3 times more.

For this reason, it is important to use glucose correctly. Not only in diets, but also in proper nutrition, it is recommended to include complex carbohydrates in the diet, which slowly break down and evenly saturate the cells. Using simple carbohydrates, the release of grape sugar in large quantities begins, which immediately fills the adipose tissue. Simple and complex carbohydrates:

Simple:, confectionery, honey, sugar, jams and jams, carbonated drinks, white bread, sweet vegetables and fruits, syrups.
Complex: found in beans (peas, beans, lentils), cereals, beets, potatoes, carrots, nuts, seeds, pasta, cereals and cereals, black and rye bread, pumpkin.

Use of glucose

For several decades, mankind has learned how to get glucose in large quantities. For this, cellulose and starch hydrolysis are used. In medicine, glucose-based drugs are classified as metabolic and detoxifying.

They are able to restore and improve metabolism, and also have a beneficial effect on redox processes. The main form of release is a sublimated combination and a liquid solution.

Who benefits from glucose

Regular consumption of glucose affects the weight of the baby in the womb.

The monosaccharide does not always enter the body with food, especially if the food is poor and not combined. Indications for the use of glucose:

During pregnancy and suspected low fetal weight. Regular consumption of glucose affects the weight of the baby in the womb.
With intoxication of the body. For example, chemicals such as arsenic, acids, phosgene, carbon monoxide. Glucose is also prescribed for overdose and drug poisoning.
With collapse and hypertensive crisis.
After poisoning as a restorative agent. Especially with dehydration against the background, vomiting or in the postoperative period.
With hypoglycemia, or low blood sugar. Suitable for diabetes, checked regularly with glucometers and analyzers.
Diseases of the liver, intestinal pathologies against the background of infections, with hemorrhagic diathesis.
It is used as a restorative agent after prolonged infectious diseases.

Release form

There are three forms of glucose release:

intravenous solution. It is prescribed to increase osmotic blood pressure, as a diuretic, to dilate blood vessels, to relieve swelling of tissues and remove excess fluid, to restore the metabolic process in the liver, and also as nutrition for the myocardium and heart valves. Produced in the form of dried grape sugar, which dissolves in concentrates with different percentages.
. Assign to improve the general condition, physical and intellectual activity. Acts as a sedative and vasodilator. One tablet contains at least 0.5 grams of dry glucose.
Solutions for infusions (droppers, systems). Assign to restore water-electrolyte and acid-base balance. Also used in dry form with a concentrated solution.

How to check your blood sugar level, learn from the video:

Contraindications and side effects

Glucose is not prescribed for people suffering from diabetes and pathologies that increase blood sugar levels. With the wrong appointment or self-medication, acute heart failure, loss of appetite and violation of the insular apparatus may occur.

It is also impossible to inject glucose intramuscularly, as this can cause necrosis of the subcutaneous fat. With the rapid introduction of a liquid solution, hyperglucosuria, hypervolemia, osmotic diuresis and hyperglycemia may occur.

Unusual uses of glucose

Glucose is used in baking for softness and freshness of the product.

In the form of syrup, grape sugar is added to the dough when baking bread. Because of this, the bread is able to be stored at home for a long time, not stale or dry out.

You can also make such bread, but using glucose in ampoules. Grape sugar in a liquid candied form is added to baked goods, such as muffins or cakes.

Glucose provides softness and long-lasting freshness to confectionery products. Dextrose is also an excellent preservative.

Eye baths, or rinsing, with a dextrose-based solution. This method helps to get rid of vascularized corneal opacity, especially after keratitis. Baths are used according to strict instructions to prevent delamination of the cornea layer. Also, glucose is dripped into the eye, using in the form of homemade drops or diluted.

Used for finishing textiles. A weak glucose solution is used as a top dressing for withering plants. For this, grape sugar is purchased in an ampoule or dry form, added to water (1 ampoule: 1 liter). Such water is regularly watered with flowers as it dries. Thanks to this, the plants will again become green, strong and healthy.

Dry glucose syrup is added to baby food. Also used during diets. It is important to monitor your health at any age, so it is recommended to pay attention to the amount of monosaccharides that are eaten along with easily digestible carbohydrates.

With a deficiency or excess of glucose, failures occur in the cardiovascular, endocrine, and nervous systems, while brain activity is significantly reduced, metabolic processes are disrupted, and immunity deteriorates. Help your body by using only wholesome foods such as fruits, honey, vegetables and grains. Limit yourself from unnecessary calories that enter the body along with waffles, cookies, pastries and cakes.

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Glucose enters the body with food, then it is absorbed by the digestive system and enters the blood, which, in turn, carries it to all organs and tissues. This is the main source of energy for the human body, it can be with gasoline, which runs most cars, or with electricity, which is necessary for the functioning of technology. In order to penetrate into the cells, it, being in the circulatory system, is placed in a shell of insulin.

Insulin is a special hormone produced by the pancreas. Without it, glucose will not be able to get inside the cells, but will not be absorbed. If there is a problem with the production of insulin, then the person becomes ill with diabetes. He needs permanent. The blood of a diabetic patient will be supersaturateduntil the body receives the missing hormone from the outside. An insulin capsule is necessary for the absorption of glucose by muscle and adipose tissues, the liver, but some organs are able to receive glucose without it. These are the heart, kidneys, liver, lens, nervous system, including the brain.

In the digestive system, glucose is absorbed very quickly. This substance is a monomer that makes up important polysaccharides such as glycogen, cellulose and starch. In glucose is oxidized, due to the release of energy, which is spent on all kinds of physiological processes.

If an excess amount of glucose enters the body, then it is quickly utilized, turning into energy reserves. On its basis, glycogen is formed, which is then deposited in various places and tissues of the body, as a reserve source of energy. If there is already enough glycogen in the cell depot, then glucose begins to turn into fat and be deposited in the body.

Glycogen is vital for muscles. It is he who, during the decay, gives the energy necessary for the work and restoration of cells. In the muscles, it is consumed constantly, but the reserves do not decrease. This is due to the fact that new portions of glycogen are constantly coming from the liver so that its level always remains constant.

A normal fasting blood glucose level is 3.5 to 6.1 mmol/liter. Elevated blood sugar is hyperglycemia. The causes of this condition can be various diseases, including diabetes mellitus and metabolic disorders. This is usually diagnosed through a urine test, through which the body will excrete sugar. Short-term hyperglycemia can be caused by various phenomena, such as overexertion, eating a lot of sweets, and others.

Too low blood glucose concentration hypoglycemia. Short-term hypoglycemia occurs when a person eats a lot of fast-digesting carbohydrates, then the sugar level first jumps sharply, and then drops sharply. Permanent hypoglycemia appears due to metabolic disorders, liver or kidney disease, as well as a lack of carbohydrates in the diet. Symptoms - trembling in the limbs, dizziness, hunger, pallor, a feeling of fear.

The correct diagnosis can only be made by a qualified specialist on the basis of the collected history and tests. For the correct interpretation of the result "sugar in the urine" it is necessary to know the processes in which certain changes occur in the body, leading to a deviation in the determination of this indicator in the biological material.

The concept of "sugar in the urine"

In a normal healthy body, there is a renal threshold for glucose, that is, a certain amount of blood sugar is reabsorbed by the kidneys in full. In view of this, sugar in the urine is not detected by qualitative methods. The established threshold slightly decreases with age. With an increase in blood glucose, the renal tubules are unable to absorb as much sugar from the urine into the blood. The result of this process is the appearance of sugar in the urine - glucosuria. The presence of sugar in the urine is a dangerous indicator in which it is necessary to identify the cause of its appearance.

Physiological glucosuria

Physiological glucosuria are observed with a single detection of sugar in the urine. Depending on the reasons that caused the change in this indicator, several forms of glucosuria are distinguished: alimentary, emotional, physical. An alimentary increase in sugar in the urine is associated with eating foods rich in carbohydrates: chocolate, sweets, sweet fruits. Emotional glucosuria occurs as a result of experienced stress, overexcitation. The appearance of glucose in the urine can be triggered by excessive physical exertion that takes place on the eve of the test. A small amount of sugar in the urine is acceptable.

Pathological glucosuria

The development of pathological glucosuria is associated with the presence of changes in the body that affect the reabsorption function of the kidneys. Diabetes is one of the most common causes of this pathology. In this case, with a sufficiently low level of sugar in the blood, it is determined in the urine in large quantities. This is more common in insulin-dependent diabetes mellitus. Acute pancreatitis can cause sugar in the urine. Brain tumor, meningitis, traumatic brain injury, hemorrhagic stroke, or encephalitis can lead to glucosuria.

Diseases that are accompanied by fever may be accompanied by febrile glucosuria. An increase in the level of adrenaline, glucocorticoid hormones, thyroxine or somatotropin can lead to the development of endocrine glucosuria. In case of poisoning with morphine, strychnine, chloroform and phosphorus, it is possible to determine toxic glucosuria. Due to a decrease in the threshold of the kidneys, renal glucosuria develops.

Preparation for analysis

On the eve of passing urine for sugar testing, you should follow a diet that excludes the use of sugary foods and fruits, drinks containing a large amount of carbohydrates. It is recommended to reduce the level of physical activity. If you detect any amount of sugar in your urine, you should immediately seek medical advice.

The role of vitamin C in the human body

On average, the human body needs about 80 mg of ascorbic acid per day, while the daily requirement for other vitamins is much lower. Why? Yes, because vitamin C normalizes the metabolism of carbohydrates, fats and proteins, increases immune defense, stimulates the formation of antibodies, red blood cells and, to a lesser extent, white ones. In addition, it reduces the concentration of glucose in the blood and increases the reserves of glycogen in the liver, normalizes the amount of cholesterol in the blood and serves as a cancer prevention.

Ascorbic acid is involved in more than 300 biological processes in the body. Of these, it is especially possible to distinguish the synthesis of collagen - a protein that forms a connective tissue that "cements" the intercellular space. Collagen is involved in the formation of tissues, bones, skin, tendons, ligaments, cartilage, teeth, etc. It protects the body from diseases and infections and accelerates wound healing.

As for immunity, vitamin C is responsible for the production of antibodies and the work of white blood cells. Without it, the formation of interferon is impossible - a substance that fights viruses and cancer. Ascorbic acid is a powerful natural water-soluble antioxidant that protects against the damaging effects of oxidizing agents. It eliminates potentially harmful reactions in water-saturated parts of the body and protects “good” cholesterol from the effects of free radicals, preventing the development of heart and vascular diseases, early aging and the development of malignant tumors.

What else lies in the area of responsibility of vitamin C

Ascorbic acid is an important component of the synthesis of hormones by the adrenal glands. Under stress, the adrenal glands begin to experience a lack of this vitamin. In addition, he takes part in the production of cholesterol and its transformation into bile. Ascorbic acid is necessary for the normal functioning of neurotransmitters in the brain. It converts tryptophan to serotonin, tyrosine to dopamine and adrenaline.

A lack of vitamin C can adversely affect the work of all organs and systems of the body, causing muscle pain, weakness, lethargy, apathy, hypotension, disruption of the digestive tract, dry skin, heart pain, tooth loss, etc.

The main message of most strict diets is "stop passing and you will be happy"! Try to understand the mechanisms of your body and lose weight wisely!

Why are we getting fat?

The answer lies on the surface - day after day we create all the most necessary conditions for this. What does our average working day look like? A cup of coffee with a couple of sandwiches, 1.5 hours of traffic jams to the office, 8 hours of sitting and a computer, then again 1.5 hours of traffic jams. Snacking anything during the day and a rich high-calorie dinner at night. On weekends - felting until noon and again the "holiday" of the stomach. Rest, after all, after all ... Okay, maybe not quite like that, and a couple of times a week we diligently spend an hour or two in the gym. But this is a drop in the ocean.

What are the types of fat?

1. Subcutaneous. This is a superficial fat that lies under the skin tissue. This is exactly the type of fat that is visible visually and that you can touch and feel. First of all, the human body begins to accumulate fat in the most problematic places. In men, this is the abdominal region and chest, in women, the hips, buttocks and sides. As these zones fill up, fat begins to explore new territories.

2. Visceral. This is a deep-seated fat, which is located around the internal organs of a person (liver, lungs, heart). To the extent visceral fat is necessary, as it provides cushioning to the internal organs. But when the subcutaneous fat has mastered all possible zones and the stages of obesity have come, it begins to replenish the reserves of visceral fat. Excess visceral fat is very dangerous because it can lead to serious health problems (diseases of the digestive and cardiovascular systems).

Why can't you just stop eating?

The Internet is full of offers of various miracle diets that promise to get rid of extra pounds in a matter of months. Their principle is usually to drastically limit the number of calories consumed. But try to understand the response mechanism of the body - the kilograms really go away, but the fat will remain unharmed. All this is explained by the presence of such a hormone as stucco. The level of its content correlates with the level of fat content - the more fat, the more stucco. So the process goes like this:

The number of calories consumed is sharply reduced, glucose levels and insulin production are reduced, fat is mobilized. Fine!
There is little glucose, which means that the level of stucco falls. The hunger signal is sent to the brain.
In response to the signal of hunger, the body turns on a protective mechanism - stopping the synthesis of muscle tissue and slowing down the burning of fat.
At the same time, the level of cortisol (stress hormone) rises, which further enhances the protective mechanism.

As you can see, weight loss occurs, but not due to fat loss, but due to a decrease in muscle mass. At the end of the diet, the body begins to intensively store calories, storing them in fat (in case the situation repeats). The difference between light and dark stripes near the tail is pronounced, and the "Volga" is considered ripe if its skin becomes light.

If you do not want to bother looking at the colors, pay attention to the size: a delicious watermelon cannot be enough. Therefore, determine at a glance the average size of the watermelon in the batch in front of you, and choose the one that will be a little larger. You should not take huge watermelons, it is quite possible that they were fairly fed with fertilizers.

If you like weird theories, try picking a watermelon based on the "boy" or "girl" principle. It is believed that in "boys" the part on which the tail is located is convex, and the circle with the tail itself is small. For "girls" this part of the "body" is flat, and the circle with a tail is large, almost the size of a five-ruble coin. It is also believed that "girls" are tastier and sweeter, they have fewer seeds.

Well, if the watermelon has a mesh or brownish dry lines on the sides, it will surely turn out to be ripe and tasty.

You can also try piercing the skin with your fingernail. Nothing will come of a ripe watermelon, its rind is very hard.

2. Beware!

If you think that it is too early to buy Russian watermelons in early August, then you are right. Most varieties reach maturity by mid or even late August. Anything that is sold earlier is likely to either not have time to ripen, or was generously fertilized to accelerate growth.

The main signs of determining that a watermelon is "stuffed" with nitrates:

Such a watermelon cannot be stored for a long time. Round spots of a darker shade appear on the skin.

When you cut it, you will see a bright red pulp and white bones, and the fibers will have a yellow color.

In the pulp there may be compacted lumps up to 2 cm in size and yellowish in color - harmful substances are concentrated in them.

The pulp of a healthy watermelon, if crushed in a glass of water, will make the water only slightly cloudy, if this watermelon, the water will turn pink or red.

3. How dangerous are nitrates?

According to doctors, no one has yet died from nitrate poisoning, but you can get in trouble. If you eat one or two slices of nitrate watermelon, then nothing will happen to you. If you get carried away and eat the whole watermelon, you can get liver problems, intestinal or nervous system disorders. If after a nice meal you feel bad, then immediately call an ambulance.

By the way, invisible nitrates are not as scary as bacteria that settle on the surface during transportation and storage. Therefore, before cutting, be sure to thoroughly wash the fruit, for a greater effect you can even scald it, it will not hurt the watermelon.

Easily digestible glucose and fructose predominate in the pulp of a ripe watermelon, sucrose accumulates if the fruit is stored for a long time. Watermelons can be eaten with diabetes, since the fructose contained in it does not cause insulin stress.

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Ministry of Education and Science of the Russian Federation

Federal State Budgetary Educational Institution of Higher Education

Tambov State University named after G.R. Derzhavin

on the topic: The biological role of glucose in the body

Completed:

Shamsidinov Shokhiyorjon Fazliddin ugli

Tambov 2016

1. Glucose

1.1 Features and functions

2.1 Glucose catabolism

2.4 Glucose synthesis in the liver

2.5 Synthesis of glucose from lactate

Used literature

1. Glucose

1.1 Features and functions

Glucomza (from other Greek glkhket sweet) (C 6 H 12 O 6), or grape sugar, or dextrose, is found in the juice of many fruits and berries, including grapes, from which the name of this type of sugar comes from. It is a monosaccharide and a six-atomic sugar (hexose). The glucose link is part of polysaccharides (cellulose, starch, glycogen) and a number of disaccharides (maltose, lactose and sucrose), which, for example, are quickly broken down into glucose and fructose in the digestive tract.

Glucose belongs to the group of hexoses, it can exist in the form of β-glucose or β-glucose. The difference between these spatial isomers lies in the fact that at the first carbon atom in β-glucose the hydroxyl group is located under the plane of the ring, and in β-glucose it is above the plane.

Glucose is a bifunctional compound, because. contains functional groups - one aldehyde and 5 hydroxyl. Thus, glucose is a polyhydric aldehyde alcohol.

The structural formula of glucose is:

Short formula

1.2 Chemical properties and structure of glucose

It has been experimentally established that aldehyde and hydroxyl groups are present in the glucose molecule. As a result of the interaction of the carbonyl group with one of the hydroxyl groups, glucose can exist in two forms: open chain and cyclic.

In glucose solution, these forms are in equilibrium with each other.

For example, in an aqueous solution of glucose, the following structures exist:

Cyclic b- and c-forms of glucose are spatial isomers that differ in the position of the hemiacetal hydroxyl relative to the plane of the ring. In β-glucose, this hydroxyl is in the trans position to the hydroxymethyl group -CH 2 OH, in β-glucose - in the cis position. Taking into account the spatial structure of the six-membered ring, the formulas of these isomers have the form:

In the solid state, glucose has a cyclic structure. Ordinary crystalline glucose is the b form. In solution, the s-form is more stable (at equilibrium, it accounts for more than 60% of the molecules). The proportion of the aldehyde form in equilibrium is insignificant. This explains the lack of interaction with fuchsine sulfuric acid (qualitative reaction of aldehydes).

For glucose, in addition to the phenomenon of tautomerism, structural isomerism with ketones is characteristic (glucose and fructose are structural interclass isomers)

Chemical properties of glucose:

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 Ov + 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

1.3 Biological significance of glucose

Glucose is a necessary component of food, one of the main participants in the body's metabolism, it is very nutritious and easily digestible. When it is oxidized, more than a third of the energy used in the body is released - the resource - fats, but the role of fats and glucose in the energy of different organs is different. The heart uses fatty acids as fuel. Skeletal muscles need glucose to “start”, but nerve cells, including brain cells, work only on glucose. Their need is 20-30% of the generated energy. Nerve cells need energy every second, and the body receives glucose when eating. Glucose is easily absorbed by the body, so it is used in medicine as a strengthening remedy. Specific oligosaccharides determine the blood type. In the confectionery business for the manufacture of marmalade, caramel, gingerbread, etc. Of great importance are the processes of fermentation of glucose. So, for example, when pickling cabbage, cucumbers, milk, lactic acid fermentation of glucose occurs, as well as when ensiling feed. In practice, alcoholic fermentation of glucose is also used, for example, in the production of beer. Cellulose is the starting material for the production of silk, cotton wool, and paper.

Carbohydrates are indeed the most common organic substances on Earth, without which the existence of living organisms is impossible.

In a living organism, in the process of metabolism, glucose is oxidized with the release of a large amount of energy:

C 6 H 12 O 6 + 6O 2 ??? 6CO 2 +6H 2 O+2920kJ

2. The biological role of glucose in the body

Glucose is the main product of photosynthesis and is formed in the Calvin cycle. In humans and animals, glucose is the main and most versatile source of energy for metabolic processes.

2.1 Glucose catabolism

Glucose catabolism is the main supplier of energy for the vital processes of the body.

Aerobic breakdown of glucose is its ultimate oxidation to CO 2 and H 2 O. This process, which is the main pathway for glucose catabolism in aerobic organisms, can be expressed by the following summary equation:

C 6 H 12 O 6 + 6O 2 > 6CO 2 + 6H 2 O + 2820 kJ / mol

Aerobic breakdown of glucose includes several stages:

* aerobic glycolysis - the process of oxidizing glucose with the formation of two molecules of pyruvate;

* the general path of catabolism, including the conversion of pyruvate to acetyl-CoA and its further oxidation in the citrate cycle;

* the chain of electron transfer to oxygen, coupled with dehydrogenation reactions that occur during the breakdown of glucose.

In certain situations, the provision of oxygen to tissues may not meet their needs. For example, in the initial stages of intense muscle work under stress, heart rate may not reach the desired frequency, and the oxygen demand of muscles for aerobic glucose breakdown is high. In such cases, a process is activated that proceeds without oxygen and ends with the formation of lactate from pyruvic acid.

This process is called anaerobic breakdown, or anaerobic glycolysis. Anaerobic breakdown of glucose is energetically inefficient, but it is this process that can become the only source of energy for a muscle cell in the situation described. In the future, when the supply of oxygen to the muscles is sufficient as a result of the transition of the heart to an accelerated rhythm, anaerobic decay switches to aerobic.

Aerobic glycolysis is the process of oxidizing glucose to pyruvic acid in the presence of oxygen. All enzymes that catalyze the reactions of this process are localized in the cytosol of the cell.

1. Stages of aerobic glycolysis

In aerobic glycolysis, 2 stages can be distinguished.

1. The preparatory stage, during which glucose is phosphorylated and split into two phosphotriose molecules. This series of reactions takes place using 2 ATP molecules.

2. Stage associated with the synthesis of ATP. As a result of this series of reactions, phosphotrioses are converted to pyruvate. The energy released at this stage is used to synthesize 10 moles of ATP.

2. Reactions of aerobic glycolysis

The conversion of glucose-6-phosphate into 2 molecules of glyceraldehyde-3-phosphate

Glucose-6-phosphate, formed as a result of ATP-assisted phosphorylation of glucose, is converted to fructose-6-phosphate during the next reaction. This reversible isomerization reaction proceeds under the action of the enzyme glucose phosphate isomerase.

Pathways of glucose catabolism. 1 - aerobic glycolysis; 2, 3 - general path of catabolism; 4 - aerobic breakdown of glucose; 5 - anaerobic breakdown of glucose (framed); 2 (circled) - stoichiometric coefficient.

Conversion of glucose-6-phosphate to triose phosphates.

Conversion of glyceraldehyde-3-phosphate to 3-phosphoglycerate.

This part of aerobic glycolysis includes the reactions associated with the synthesis of ATP. The most complex reaction in this series of reactions is the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate. This transformation is the first oxidation reaction during glycolysis. The reaction is catalyzed by glyceraldehyde-3-phosphate dehydrogenase, which is a NAD-dependent enzyme. The significance of this reaction lies not only in the fact that a reduced coenzyme is formed, the oxidation of which in the respiratory chain is associated with the synthesis of ATP, but also in the fact that the free energy of oxidation is concentrated in the macroergic bond of the reaction product. Glyceraldehyde-3-phosphate dehydrogenase contains a cysteine residue in the active center, the sulfhydryl group of which is directly involved in catalysis. Oxidation of glyceraldehyde-3-phosphate leads to the reduction of NAD and the formation with the participation of H 3 PO 4 of a high-energy anhydride bond in 1,3-bisphosphoglycerate at position 1. In the next reaction, high-energy phosphate is transferred to ADP with the formation of ATP

The formation of ATP in this way is not associated with the respiratory chain, and it is called substrate ADP phosphorylation. The formed 3-phosphoglycerate no longer contains a macroergic bond. In the following reactions, intramolecular rearrangements occur, the meaning of which boils down to the fact that a low-energy phosphoester passes into a compound containing a high-energy phosphate. Intramolecular transformations consist in the transfer of a phosphate residue from position 3 in phosphoglycerate to position 2. Then a water molecule is split off from the resulting 2-phosphoglycerate with the participation of the enolase enzyme. The name of the dehydrating enzyme comes from the reverse reaction. As a result of the reaction, a substituted enol is formed - phosphoenolpyruvate. The resulting phosphoenolpyruvate is a macroergic compound, the phosphate group of which is transferred in the next reaction to ADP with the participation of pyruvate kinase (the enzyme is also named after the reverse reaction in which pyruvate is phosphorylated, although such a reaction does not take place in this form).

Conversion of 3-phosphoglycerate to pyruvate.

3. Oxidation of cytoplasmic NADH in the mitochondrial respiratory chain. Shuttle systems

NADH, formed during the oxidation of glyceraldehyde-3-phosphate in aerobic glycolysis, undergoes oxidation by the transfer of hydrogen atoms into the mitochondrial respiratory chain. However, cytosolic NADH is unable to transfer hydrogen to the respiratory chain because the mitochondrial membrane is impermeable to it. The transfer of hydrogen through the membrane occurs with the help of special systems called "shuttle". In these systems, hydrogen is transported through the membrane with the participation of pairs of substrates bound by the corresponding dehydrogenases, i.e. on both sides of the mitochondrial membrane is a specific dehydrogenase. 2 shuttle systems are known. In the first of these systems, hydrogen is transferred from NADH in the cytosol to dihydroxyacetone phosphate by the enzyme glycerol-3-phosphate dehydrogenase (NAD-dependent enzyme, named after the reverse reaction). The glycerol-3-phosphate formed during this reaction is further oxidized by the enzyme of the inner mitochondrial membrane - glycerol-3-phosphate dehydrogenase (FAD-dependent enzyme). Then protons and electrons from FADH 2 pass to ubiquinone and further along the CPE.

The glycerol phosphate shuttle system works in white muscle cells and hepatocytes. However, mitochondrial glycerol-3-phosphate dehydrogenase is absent in cardiac muscle cells. The second shuttle system, which involves malate, cytosolic and mitochondrial malate dehydrogenases, is more universal. In the cytoplasm, NADH reduces oxaloacetate to malate, which, with the participation of a carrier, passes into mitochondria, where it is oxidized to oxaloacetate by NAD-dependent malate dehydrogenase (reaction 2). The NAD reduced during this reaction donates hydrogen to the mitochondrial CPE. However, oxaloacetate formed from malate cannot exit the mitochondria into the cytosol on its own, since the mitochondrial membrane is impermeable to it. Therefore, oxaloacetate is converted to aspartate, which is transported to the cytosol, where it is again converted to oxaloacetate. The conversion of oxaloacetate to aspartate and vice versa is associated with the addition and elimination of an amino group. This shuttle system is called malate-aspartate. The result of her work is the regeneration of cytoplasmic NAD+ from NADH.

Both shuttle systems differ significantly in the amount of ATP synthesized. In the first system, the P/O ratio is 2, since hydrogen is introduced into the CPE at the level of KoQ. The second system is energetically more efficient, since it transfers hydrogen to the CPE through mitochondrial NAD+ and the P/O ratio is close to 3.

4. ATP balance during aerobic glycolysis and breakdown of glucose to CO 2 and H 2 O.

ATP release during aerobic glycolysis

The formation of fructose-1,6-bisphosphate from one glucose molecule requires 2 ATP molecules. Reactions associated with the synthesis of ATP occur after the breakdown of glucose into 2 molecules of phosphotriose, i.e. in the second step of glycolysis. At this stage, 2 reactions of substrate phosphorylation occur and 2 ATP molecules are synthesized. In addition, one molecule of glyceraldehyde-3-phosphate is dehydrogenated (reaction 6), and NADH transfers hydrogen to the mitochondrial CPE, where 3 ATP molecules are synthesized by oxidative phosphorylation. In this case, the amount of ATP (3 or 2) depends on the type of shuttle system. Therefore, the oxidation to pyruvate of one molecule of glyceraldehyde-3-phosphate is associated with the synthesis of 5 ATP molecules. Considering that 2 phosphotriose molecules are formed from glucose, the resulting value must be multiplied by 2 and then subtract 2 ATP molecules consumed in the first stage. Thus, the output of ATP during aerobic glycolysis is (5×2) - 2 = 8 ATP.

The release of ATP during the aerobic breakdown of glucose to end products as a result of glycolysis produces pyruvate, which is further oxidized to CO 2 and H 2 O in the OPC. Now we can evaluate the energy efficiency of glycolysis and OPC, which together make up the process of aerobic breakdown of glucose to end products. Thus, the ATP yield when 1 mol of glucose is oxidized to CO 2 and H 2 O is 38 mol of ATP. In the process of aerobic breakdown of glucose, 6 dehydrogenation reactions occur. One of them occurs in glycolysis and 5 in the GPC. Substrates for specific NAD-dependent dehydrogenases: glyceraldehyde-3-phosphate, zhiruvate, isocitrate, β-ketoglutarate, malate. One dehydrogenation reaction in the citrate cycle under the action of succinate dehydrogenase occurs with the participation of the FAD coenzyme. The total amount of ATP synthesized by oxidative phosphorylation is 17 mol of ATP per 1 mol of glyceraldehyde phosphate. To this must be added 3 mol of ATP synthesized by substrate phosphorylation (two reactions in glycolysis and one in the citrate cycle). Considering that glucose breaks down into 2 phosphotrioses and that the stoichiometric coefficient of further transformations is 2, the resulting value must be multiplied by 2, and subtract from the result 2 mol of ATP used in the first stage of glycolysis.

Anaerobic breakdown of glucose (anaerobic glycolysis).

Anaerobic glycolysis is the process of breaking down glucose to form lactate as an end product. This process proceeds without the use of oxygen and therefore does not depend on the functioning of the mitochondrial respiratory chain. ATP is formed by substrate phosphorylation reactions. The overall equation of the process:

C 6 H 12 0 6 + 2 H 3 P0 4 + 2 ADP \u003d 2 C 3 H 6 O 3 + 2 ATP + 2 H 2 O.

anaerobic glycolysis.

During anaerobic glycolysis, all 10 reactions identical to aerobic glycolysis occur in the cytosol. Only reaction 11, where pyruvate is reduced by cytosolic NADH, is specific for anaerobic glycolysis. The reduction of pyruvate to lactate is catalyzed by lactate dehydrogenase (the reaction is reversible, and the enzyme is named after the reverse reaction). This reaction ensures the regeneration of NAD+ from NADH without the participation of the mitochondrial respiratory chain in situations associated with insufficient oxygen supply to cells.

2.2 Significance of glucose catabolism

The main physiological purpose of glucose catabolism is to use the energy released in this process for the synthesis of ATP.

Aerobic breakdown of glucose occurs in many organs and tissues and serves as the main, although not the only, source of energy for life. Some tissues are most dependent on glucose catabolism for energy. For example, brain cells consume up to 100 g of glucose per day, oxidizing it aerobically. Therefore, insufficient supply of glucose to the brain or hypoxia are manifested by symptoms indicating a violation of brain functions (dizziness, convulsions, loss of consciousness).

Anaerobic breakdown of glucose occurs in muscles, in the first minutes of muscular work, in erythrocytes (which lack mitochondria), as well as in various organs under conditions of limited oxygen supply, including tumor cells. The metabolism of tumor cells is characterized by the acceleration of both aerobic and anaerobic glycolysis. But predominant anaerobic glycolysis and an increase in lactate synthesis serve as an indicator of an increased rate of cell division with insufficient provision of them with a system of blood vessels.

In addition to the energy function, the process of glucose catabolism can also perform anabolic functions. Glycolysis metabolites are used to synthesize new compounds. Thus, fructose-6-phosphate and glyceraldehyde-3-phosphate are involved in the formation of ribose-5-phosphate, a structural component of nucleotides; 3-phosphoglycerate can be involved in the synthesis of amino acids such as serine, glycine, cysteine (see section 9). In the liver and adipose tissue, acetyl-CoA, formed from pyruvate, is used as a substrate for the biosynthesis of fatty acids, cholesterol, and dihydroxyacetone phosphate as a substrate for the synthesis of glycerol-3-phosphate.

Recovery of pyruvate to lactate.

2.3 Regulation of glucose catabolism

Since the main significance of glycolysis is the synthesis of ATP, its rate should correlate with the energy expenditure in the body.

Most of the reactions of glycolysis are reversible, with the exception of three catalyzed by hexokinase (or glucokinase), phosphofructokinase, and pyruvate kinase. Regulatory factors that change the rate of glycolysis, and hence the formation of ATP, are aimed at irreversible reactions. An indicator of ATP consumption is the accumulation of ADP and AMP. The latter is formed in a reaction catalyzed by adenylate kinase: 2 ADP - AMP + ATP

Even a small consumption of ATP leads to a noticeable increase in AMP. The ratio of the level of ATP to ADP and AMP characterizes the energy status of the cell, and its components serve as allosteric regulators of the rate of both the general path of catabolism and glycolysis.

Essential for the regulation of glycolysis is a change in the activity of phosphofructokinase, because this enzyme, as mentioned earlier, catalyzes the slowest reaction of the process.

Phosphofructokinase is activated by AMP but inhibited by ATP. AMP, by binding to the allosteric center of phosphofructokinase, increases the affinity of the enzyme for fructose-6-phosphate and increases the rate of its phosphorylation. The effect of ATP on this enzyme is an example of homotropic Auschüsterism, since ATP can interact with both the allosteric and the active site, in the latter case as a substrate.

At physiological values of ATP, the active center of phosphofructokinase is always saturated with substrates (including ATP). An increase in the level of ATP relative to ADP reduces the reaction rate, since under these conditions ATP acts as an inhibitor: it binds to the allosteric center of the enzyme, causes conformational changes, and reduces the affinity for its substrates.

Changes in the activity of phosphofructokinase contribute to the regulation of the rate of glucose phosphorylation by hexokinase. A decrease in phosphofructokinase activity at a high level of ATP leads to the accumulation of both fructose-6-phosphate and glucose-6-phosphate, and the latter inhibits hexokinase. It should be recalled that hexokinase in many tissues (with the exception of the liver and pancreatic β-cells) is inhibited by glucose-6-phosphate.

High ATP levels decrease the rate of the citric acid cycle and the respiratory chain. Under these conditions, the process of glycolysis also slows down. It should be recalled that the allosteric regulation of the OPC and respiratory chain enzymes is also associated with changes in the concentration of such key products as NADH, ATP, and some metabolites. So, NADH, accumulating if it does not have time to be oxidized in the respiratory chain, inhibits some allosteric enzymes of the citrate cycle.

Regulation of glucose catabolism in skeletal muscle.

2.4 Synthesis of glucose in the liver (gluconeogenesis)

Some tissues, such as the brain, need a constant supply of glucose. When the intake of carbohydrates in the diet is not enough, the blood glucose content is maintained within the normal range for some time due to the breakdown of glycogen in the liver. However, glycogen stores in the liver are low. They significantly decrease by 6-10 hours of fasting and are almost completely exhausted after a daily fast. In this case, de novo glucose synthesis begins in the liver - gluconeogenesis.

Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate substances. Its main function is to maintain blood glucose levels during prolonged fasting and intense physical exertion. The process proceeds mainly in the liver and less intensively in the cortical substance of the kidneys, as well as in the intestinal mucosa. These tissues can provide the synthesis of 80-100 g of glucose per day. The brain during fasting accounts for most of the body's need for glucose. This is due to the fact that brain cells are not able, unlike other tissues, to provide energy needs due to the oxidation of fatty acids. In addition to the brain, tissues and cells in which the aerobic pathway of decay is impossible or limited, such as erythrocytes (they lack mitochondria), cells of the retina, adrenal medulla, etc., need glucose.

The primary substrates for gluconeogenesis are lactate, amino acids, and glycerol. The inclusion of these substrates in gluconeogenesis depends on the physiological state of the organism.

Lactate is a product of anaerobic glycolysis. It is formed in all conditions of the body in red blood cells and working muscles. Thus, lactate is constantly used in gluconeogenesis.

Glycerol is released during the hydrolysis of fats in adipose tissue during fasting or during prolonged physical exertion.

Amino acids are formed as a result of the breakdown of muscle proteins and are included in gluconeogenesis during prolonged fasting or prolonged muscular work.

2.5 Synthesis of glucose from lactate

Lactate formed in anaerobic glycolysis is not a metabolic end product. The use of lactate is associated with its conversion in the liver to pyruvate. Lactate as a source of pyruvate is important not only during fasting, but during the normal functioning of the body. Its conversion to pyruvate and further use of the latter is a way to utilize lactate. Lactate, formed in intensively working muscles or in cells with a predominantly anaerobic way of glucose catabolism, enters the bloodstream and then to the liver. In the liver, the NADH/NAD+ ratio is lower than in the contracting muscle; therefore, the lactate dehydrogenase reaction proceeds in the opposite direction, i.e. towards the formation of pyruvate from lactate. Further, pyruvate is included in gluconeogenesis, and the resulting glucose enters the bloodstream and is absorbed by skeletal muscles. This sequence of events is called the "glucose-lactate cycle" or "Cori cycle". The Corey cycle performs 2 important functions: 1 - ensures the utilization of lactate; 2 - prevents the accumulation of lactate and, as a consequence, a dangerous decrease in pH (lactic acidosis). Part of the pyruvate formed from lactate is oxidized by the liver to CO 2 and H 2 O. The energy of oxidation can be used to synthesize ATP, which is necessary for gluconeogenesis reactions.

Corey cycle (glucose lactate cycle). 1 - receipt of layugat from the contracting muscle with blood flow to the liver; 2 - synthesis of glucose from lactate in the liver; 3 - the flow of glucose from the liver with blood flow into the working muscle; 4 - the use of glucose as an energy substrate by the contracting muscle and the formation of lactate.

Lactic acidosis. The term "acidosis" means an increase in the acidity of the body's environment (decrease in pH) to values that are outside the normal range. Acidosis either increases proton production or decreases proton excretion (in some cases both). Metabolic acidosis occurs with an increase in the concentration of intermediate metabolic products (acidic in nature) due to an increase in their synthesis or a decrease in the rate of decay or excretion. If the acid-base state of the body is disturbed, buffer compensation systems are quickly activated (after 10-15 minutes). Pulmonary compensation ensures the stabilization of the ratio of HCO 3 -/H 2 CO 3 , which normally corresponds to 1:20, and decreases with acidosis. Pulmonary compensation is achieved by increasing the volume of ventilation and, consequently, by accelerating the removal of CO 2 from the body. However, the main role in the compensation of acidosis is played by renal mechanisms with the participation of ammonia buffer. One of the causes of metabolic acidosis may be the accumulation of lactic acid. Normally, lactate in the liver is converted back to glucose by gluconeogenesis or oxidized. In addition to the liver, other consumers of lactate are the kidneys and the heart muscle, where lactate can be oxidized to CO 2 and H 2 O and used as an energy source, especially during physical work. The level of lactate in the blood is the result of a balance between the processes of its formation and utilization. Short-term compensated lactic acidosis occurs quite often even in healthy people with intense muscular work. In untrained people, lactic acidosis during physical work occurs as a result of a relative lack of oxygen in the muscles and develops quite quickly. Compensation is carried out by hyperventilation.

With uncompensated lactic acidosis, the content of lactate in the blood increases to 5 mmol / l (normally up to 2 mmol / l). In this case, the pH of the blood can be 7.25 or less (normally 7.36-7.44). An increase in blood lactate may be due to a disorder in pyruvate metabolism.

Disorders of pyruvate metabolism in lactic acidosis. 1 - violation of the use of pyruvate in gluconeogenesis; 2 - violation of pyruvate oxidation. glucose biological catabolism gluconeogenesis

Thus, during hypoxia, which occurs as a result of a disruption in the supply of tissues with oxygen or blood, the activity of the pyruvate dehydrogenase complex decreases and the oxidative decarboxylation of pyruvate decreases. Under these conditions, the equilibrium of the reaction pyruvate - lactate is shifted towards the formation of lactate. In addition, during hypoxia, ATP synthesis decreases, which consequently leads to a decrease in the rate of gluconeogenesis, another pathway for lactate utilization. An increase in lactate concentration and a decrease in intracellular pH negatively affect the activity of all enzymes, including pyruvate carboxylase, which catalyzes the initial reaction of gluconeogenesis.

The occurrence of lactic acidosis is also facilitated by violations of gluconeogenesis in liver failure of various origins. In addition, hypovitaminosis B 1 may be accompanied by lactic acidosis, since the derivative of this vitamin (thiamine diphosphate) performs a coenzyme function in the PDC during the oxidative decarboxylation of pyruvate. Thiamine deficiency can occur, for example, in alcoholics with a disturbed diet.

So, the reasons for the accumulation of lactic acid and the development of lactic acidosis can be:

activation of anaerobic glycolysis due to tissue hypoxia of various origins;

liver damage (toxic dystrophy, cirrhosis, etc.);

violation of the use of lactate due to hereditary defects in gluconeogenesis enzymes, insufficiency of glucose-6-phosphatase;

violation of the MPC due to defects in enzymes or hypovitaminosis;

the use of a number of drugs, such as biguanides (gluconeogenesis blockers used in the treatment of diabetes mellitus).

2.6 Synthesis of glucose from amino acids

Under conditions of starvation, part of the proteins in muscle tissue breaks down to amino acids, which are then included in the process of catabolism. Amino acids that catabolize into pyruvate or citrate cycle metabolites can be considered as potential precursors of glucose and glycogen and are called glycogenic. For example, oxaloacetate, formed from aspartic acid, is an intermediate product of both the citrate cycle and gluconeogenesis.

Of all the amino acids entering the liver, approximately 30% is accounted for by alanine. This is due to the fact that during the breakdown of muscle proteins, amino acids are formed, many of which are converted immediately to pyruvate or first to oxaloacetate, and then to pyruvate. The latter turns into alanine, acquiring an amino group from other amino acids. Alanine from the muscles is transported by the blood to the liver, where it is again converted to pyruvate, which is partially oxidized and partially included in glucose neogenesis. Therefore, there is the following sequence of events (glucose-alanine cycle): muscle glucose > muscle pyruvate > muscle alanine > liver alanine > liver glucose > muscle glucose. The whole cycle does not lead to an increase in the amount of glucose in the muscles, but it solves the problems of transporting amine nitrogen from the muscles to the liver and prevents lactic acidosis.

Glucose-alanine cycle

2.7 Synthesis of glucose from glycerol

Glycerol can only be used in tissues that contain the enzyme glycerol kinase, such as the liver, kidneys. This ATP-dependent enzyme catalyses the conversion of glycerol to β-glycerophosphate (glycerol-3-phosphate). When glycerol-3-phosphate is included in gluconeogenesis, it is dehydrogenated by NAD-dependent dehydrogenase to form dihydroxyacetone phosphate, which is then converted into glucose.

The conversion of glycerol to dihydroxyacetone phosphate

Thus, we can say that the biological role of glucose in the body is very large. Glucose is one of the main energy source of our body. It is an easily digestible source of valuable nutrition that increases the energy reserves of the body and improves its functions. The main value in the body is that it is the most versatile source of energy for metabolic processes.

In the human body, the use of hypertonic glucose solution promotes vasodilation, increased contractile activity of the heart muscle and an increase in urine volume. As a general tonic, glucose is used in chronic diseases that are accompanied by physical exhaustion. The detoxifying properties of glucose are due to its ability to activate the functions of the liver to neutralize poisons, as well as a decrease in the concentration of toxins in the blood as a result of an increase in the volume of circulating fluid and increased urination. In addition, in animals it is deposited in the form of glycogen, in plants - in the form of starch, the glucose polymer - cellulose is the main component of the cell membranes of all higher plants. In animals, glucose helps to survive frosts.

In short, glucose is one of the vital substances in the life of living organisms.

List of used literature

1. Biochemistry: a textbook for universities / ed. E.S. Severina - 5th ed., - 2014. - 301-350 st.

2. T.T. Berezov, B.F. Korovkin Biological Chemistry.

3. Clinical endocrinology. Guide / N. T. Starkova. - 3rd edition, revised and expanded. - St. Petersburg: Peter, 2002. - S. 209-213. - 576 p.

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