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 having a highly branched chain of glucose residues. In this article we will tell you all about glycogen: what it is, what are their functions, where are they stored. We will also describe what deviations occur during their synthesis.
Glycogenes: what is it and how are they synthesized?
Glycogen is an essential reserve of glucose in the body. In the human body, it is synthesized as follows. During a meal, carbohydrates (including starch and disaccharides - lactose, maltose and sucrose) are broken down into small molecules by the action of an enzyme (amylase). Then, in the small intestine, enzymes such as sucrose, pancreatic amylase and maltase hydrolyze carbohydrate residues to monosaccharides, including glucose.
One part of the released glucose, entering 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 that occurs with or without oxygen (aerobic and anaerobic), ATP molecules are synthesized, which are a 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 addition 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 obtained glycogen is stored in the form of special granules in the cytoplasm (cytosol) of many body cells. The glycogen content in the liver and muscle tissue is especially high.
Moreover, muscle glycogen is a source of glucose supply for the muscle cell itself (in case of heavy load), and hepatic maintains a normal concentration of glucose in the blood. Also, a supply of these complex carbohydrates is found in nerve cells, heart cells, aorta, epithelial integument, connective tissue, uterine mucosa and embryonic tissues. So, we examined what is meant by the term "glycogen". What it is is now clear. Next, let's talk about their functions.
Why are glycogens necessary for the body?
In the body, glycogen serves as an energy reserve. In case of urgent need, the body can get the missing glucose from it. How does this happen? The breakdown of glycogen occurs 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 expense of ATP.
Why is glycogen needed in the liver?
The liver is one of the most important internal organs of the human body. It performs many diverse 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 in the normal range from 80 to 120 mg / dl are lipogenesis followed by the breakdown of glycogen, gluconeogenesis and the transformation of other sugars into glucose.
With a decrease in blood sugar, phosphorylase activates, and then the liver glycogen breaks down. Its accumulations disappear from the cytoplasm of cells, and glucose enters the bloodstream, giving the body the necessary energy. With an increase in sugar level, for example, after eating, 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 critically necessary for the normal functioning of the organ. Deviations - significant increases / decreases in blood glucose - pose a serious danger to human health.
Glycogen synthesis disorder
Glycogen metabolic disorders are a group of hereditary glycogen diseases. Their causes are various defects of 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 C6H10O5 polysaccharide in cells.
The synthesis of glycogen and its subsequent excess presence in the liver, lungs, kidneys, skeletal and cardiac muscles are caused by defects in the enzymes (for example, glucose-6-phosphatase) involved in the breakdown of glycogen. Most often, with glycogenosis, there are violations of the development of organs, a delay in psychomotor development, severe hypoglycemic conditions, up to the onset of coma. To confirm the diagnosis and determine the type of glycogenosis,
a liver and muscle
biopsy is
performed , after which the resulting material is sent for histochemical examination. During it, the content of glycogen in the tissues, as well as the activity of enzymes that contribute to its synthesis and decay, are established.
If there are no glycogens in the body, what does this mean?
Aglycogenosis is a serious hereditary disease caused by the absence of an enzyme capable of synthesizing glycogen (glycogen synthetase). In the presence of this pathology, glycogen is completely absent in the liver. The clinical manifestations of the disease are as follows: extremely low blood glucose, resulting in persistent hypoglycemic convulsions. The condition of patients is defined as extremely serious. The presence of aglycogenosis is investigated by biopsy of the liver.