Glycogen is a complex, complex carbohydrate, which in the process of glycogenesis is formed from glucose that enters the human body with food. From a chemical point of view, it is defined by the formula C6H10O5 and is a colloidal polysaccharide with a highly branched chain of glucose residues. In this article, we will tell you everything about glycogens: what they are, what their functions are, where they are stored. We will also describe what deviations there are in the process of synthesizing them.
Glycogens: what are they and how are they synthesized?
Glycogen is the body's essential reserve of glucose. In the human body, it is synthesized as follows. During meals, carbohydrates (including starch and disaccharides - lactose, m altose and sucrose) are broken down into small molecules by the action of an enzyme (amylase). Then, in the small intestine, enzymes such as sucrase, pancreatic amylase and m altase hydrolyse carbohydrate residues to monosaccharides, including glucose.
One part of the releasedglucose, having entered the bloodstream, is sent to the liver, and the other is transported to the cells of other organs. Directly in cells, including muscle cells, there is a subsequent breakdown of glucose monosaccharide, which is called glycolysis. In the process of glycolysis, which occurs with or without the participation of (aerobic and anaerobic) oxygen, ATP molecules are synthesized, which are the source of energy in all living organisms. But not all glucose that enters the human body with food is spent on ATP synthesis. Part of it is stored in the form of glycogen. The process of glycogenesis involves polymerization, that is, the sequential attachment of glucose monomers to each other and the formation of a branched polysaccharide chain under the influence of special enzymes.
Where is glycogen located?
The resulting glycogen is stored in the form of special granules in the cytoplasm (cytosol) of many body cells. The content of glycogen in the liver and muscle tissue is especially high.
Moreover, muscle glycogen is a source of glucose storage for the muscle cell itself (in case of a heavy load), and liver glycogen maintains a normal concentration of glucose in the blood. Also, the supply of these complex carbohydrates is found in nerve cells, cells of the heart, aorta, epithelial integument, connective tissue, uterine mucosa and embryonic tissues. So, we examined what is meant by the term "glycogens". What it is is now clear. Next, let's talk about their functions.
Why does the body need glycogens?
In the body, glycogen serves inas an energy reserve. In case of urgent need, the body will be able to get the missing glucose from it. How does this happen? Glycogen breakdown is carried out between meals, and is also significantly accelerated during serious physical work. This process occurs by cleavage of glucose residues under the influence of special enzymes. As a result, glycogen breaks down to free glucose and glucose-6-phosphate without the consumption of ATP.
Why is liver glycogen needed?
The liver is one of the most important internal organs of the human body. It performs many different vital functions. Including provides a normal level of sugar in the blood, necessary for the functioning of the brain. The main mechanisms by which glucose is maintained within the normal range of 80 to 120 mg/dL are lipogenesis followed by breakdown of glycogen, gluconeogenesis, and the conversion of other sugars into glucose.
When blood sugar levels drop, phosphorylase is activated, and then liver glycogen is broken down. Its accumulations disappear from the cytoplasm of cells, and glucose enters the blood, giving the body the necessary energy. With an increase in sugar levels, for example, after a meal, liver cells begin to actively synthesize glycogen and deposit it. Gluconeogenesis is the process by which the liver synthesizes glucose from other substances, including amino acids. The regulatory function of the liver makes it criticallynecessary for the normal functioning of the body. Deviations - significant increases / decreases in blood glucose levels - pose a serious danger to human he alth.
Impaired glycogen synthesis
Glycogen metabolism disorders are a group of hereditary glycogen diseases. Their causes are various defects in enzymes that are directly involved in the regulation of the formation or breakdown of glycogens. Among glycogen diseases, glycogenoses and aglycogenoses are distinguished. The former are rare hereditary pathologies caused by excessive accumulation of the C6H10O5 polysaccharide in cells.
Glycogen synthesis and its subsequent excess in the liver, lungs, kidneys, skeletal and cardiac muscles are caused by defects in enzymes (eg, glucose-6-phosphatase) involved in the breakdown of glycogen. Most often, with glycogenosis, there are developmental disorders of organs, delayed psychomotor development, severe hypoglycemic conditions, up to the onset of coma. To confirm the diagnosis and determine the type of glycogenosis, a biopsy of the liver and muscles is performed, after which the resulting material is sent for histochemical examination. During it, the content of glycogen in tissues is determined, as well as the activity of enzymes that contribute to its synthesis and breakdown.
If there is no glycogen in the body, what does it mean?
Aglycogenoses are a severe hereditary disease caused by the absence of an enzyme capable of glycogen synthesis(glycogen synthetase). In the presence of this pathology, glycogen is completely absent in the liver. The clinical manifestations of the disease are as follows: an extremely low blood glucose content, as a result of which - constant hypoglycemic convulsions. The condition of the patients is defined as extremely serious. The presence of aglycogenosis is examined by performing a liver biopsy.
