Glycogen : Structure, Function, Formula

Published on 23-Sep-2022


Glycogen is a nutritional polysaccharide, meaning they are a common energy source. Even if it is the main stored food component in animals, it also exists as the main stored food for cyanobacteria and some fungi, such as yeast. The basic building block of the substance glycogen is α-D-glucose. Like amylopectin, its molecular chain has branches. The branching occurs through a-1, 6 linkages where each branch usually contains about 10 to 20 molecules of glucose.

After hydrolysis, only a-D-glucose molecules are obtained from glycogen; its molecular symbol is C6H10O2. The liver and muscles of animals store more glycogen, which can be converted into glucose to provide carbon dioxide and energy in the form of ATP. That is why glycogen is known as animal starch. The famous French physiologist Claude Bernard discovered the Glycogen molecule back in 1857.

Properties of glycogen:

  • In general, the substance glycogen is partially soluble in water. 
  • It looks like a white, powdery biochemical substance. 
  • It leaves a reddish violet color if iodine solution is applied or used.
  • It forms like a colloidal suspension in cold water. 
  • Its red color of it disappears when it is heated. 
  • The black color of the substance returns on cooling/ when it is cooled. 
  • It is partially hydrolyzed to maltose and fully hydrolyzed to give off a-D-glucose molecules. 
  • Glycogen hydrolyzes in the process of glycolysis to form glucose molecules. 
  • Liver glycogen is converted into glucose molecules. Later, it circulates in the blood and helps regulate the normal glucose level.

Some of the uses of glycogen

(i) Glycogen stored in muscles provides energy for the muscles in our body to function correctly.

(ii) It also breaks down liver glycogen into glucose molecules.

(iii) It regulates the normal glucose level in the blood after liver glycogen is converted into glucose.

Carbohydrate derivatives

Some of the new types of carbohydrates are created or made by chemical changes. It can also be done by adding a functional group to the original structure of the carbohydrate molecule; they are known as carbohydrate derivatives. Phosphate joins the OH group of fructose to form fructose phosphate, also called sugar phosphate. It occurs in the process of forming glycolysis. OH group is then replaced by the amino group to form the substances Glucosamine and Galactosamine.

The roles of carbohydrates in living organisms:

Carbohydrates are essential for the formation of living organisms, as we all know, and the roles are:

1. The body's primary energy source is sugar, also called carbohydrates. It provides energy for our body to function as required and is essential for our diet. The energy supplied by the oxidation of carbohydrates is used in metabolism in our bodies.

2. Carbohydrates like starch, inulin, etc., are stored in various algae and plant bodies.

3. It is present as a structural component, about 50-80% of the dry weight of the plant body material.

4. Cellulose, hemicellulose, chitin, pectin, etc., are the main components of the cell wall. Animals, fungi, and bacteria store sugars called glycogen.

6. Amino and fatty acids help in metabolism, and when the body lacks protein, protein is created from carbohydrates, and needs are met.

7. Carbohydrates help the body prepare and repair itself by providing extra protein. 8. The essential building blocks of RNA and DNA are sugars called ribose and deoxyribose.

9. It also plays a role as a lubricant or slippery substance in the joints of bones in animals.

10. As building blocks of essential compounds like ATP, ADP, GTP, GDP, NAD, NADP, FAD, etc.

11. Many of the three basic human needs of food, clothing, and shelter are derived from carbohydrates. 12. Carbohydrates like cellulose give plants strength and protection and carry loads.


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