Glycogen is a nutrient complex homopolysaccharide. Glycogen is the main stored food in the animal body. Glycogen is stored in the liver, muscles, brain and stomach of vertebrates. But the liver has the most. Human liver contains about 100-120 grams of glycogen. Cyanobacteria or blue-green algae and some fungi (yeasts) have glycogen as stored food. Glycogen is called animal starch. French scientist Claude Bernard (1857) discovered glycogen.
Glycogen Properties/Religions
(i) Glycogen is a white powdery biochemical substance.
(ii) It is soluble in water. Dr. Siddiq Publications
(iii) It forms suspension in cold water.
(iv) Its molecular weight is 50 lakh daltons.
(v) On wet analysis it converts first to maltose and then to α-glucose.
(vi) It reacts with iodine solution to acquire a reddish violet color.
(vii) Heat removes its red color.
(viii) It reverts to black color on cooling.
(ix) Partially hydrolyzed to maltose and fully hydrolyzed to α-D glucose.
(x) It is converted into glucose in the process of glycolysis.
(xi) It keeps blood glucose levels normal.
Chemical structure of glycogen
Glycogen is a complex polysaccharide. It is composed of numerous α-glucose molecules. In the process of glycogenesis, 30,000 molecules of glucose combine to form glycogen. Glucose molecules are linked by α-1-4 glycosidic bonds to form glycogen. Branching of glycogen occurs through α-1-6 linkage. Each branch contains 10-20 glucose molecules. Their molecular weight is 106-107 daltons. Glycogen is hydrolyzed into glucose. Glycogen is converted to glucose when needed to provide carbon and energy. For this reason, glycogen is called animal starch.
Utilization of glycogen
(i) Stored food: Glycogen is stored in the animal body as stored food.
(ii) Glucose production: Glucose is produced from liver glycogen in the process of glycogenesis.
(iii) Muscle energy: Glycogen stored in skeletal and cardiac muscles provides extra energy to muscles.
(iv) Regulation of blood volume: It regulates blood volume in the body. Increases blood glucose levels by breaking down liver glycogen. Dr. Siddiq Publications
(v) Formation of suspension: It forms colloidal suspension in water.
(vi) Production of Surfactant: Glycogen begins to accumulate in the pulmonary cells of the fetal baby at 23 weeks of gestation. Stored glycogen produces lung surfactant.
(vii) Energy storage: Glycogen production and storage takes place in the liver cells of animals. It acts as a stored energy reservoir secondary to the glucose cycle in the animal body. Dr. Siddiq Publications
(viii) Energy supply to the brain: A small amount of glycogen is stored in brain cells. It powers the conscious brain.