Answer the question on the basis of passage given below:

Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids etc. Proteins and carbohydrates are essential constituents of our food. Carbohydrates are primarily produced by plants and form a very large group of naturally occurring organic compounds. SOme common examples are cane sugar, glucose, starch etc.

Carbohydrates are stored in animals as:

Glycogen

The correct answer is option 3. Glycogen.

Glycogen is a polysaccharide composed of glucose units linked together by both α(1→4) and α(1→6) glycosidic bonds. It is highly branched, with branches occurring approximately every 8-12 glucose units. This branching structure allows glycogen to be rapidly mobilized when glucose is needed.

Storage Locations:

Liver: In the liver, glycogen acts as a reservoir of glucose that can be released into the bloodstream to maintain blood glucose levels, especially between meals or during fasting.

Muscles: In muscle tissue, glycogen serves as an immediate source of glucose for energy production during physical activity. Muscle glycogen is not released into the bloodstream but is used locally within the muscle cells.

Function: The primary function of glycogen is to store glucose in a compact form that can be quickly broken down into glucose molecules when needed. This is crucial for maintaining energy levels and responding to fluctuations in blood glucose.

Comparison with Other Carbohydrate Forms

Glucose:

Glucose is a monosaccharide, a simple sugar that serves as a primary energy source for cells. While glucose is a key energy substrate, it is not stored in large amounts. Instead, excess glucose is converted into glycogen for storage.

Starch:

Starch is a polysaccharide composed of glucose units linked by α(1→4) and α(1→6) glycosidic bonds, similar to glycogen but less branched. Starch is the main storage carbohydrate in plants. It is found in high concentrations in foods like potatoes, rice, and corn. Unlike glycogen, starch is not used for energy storage in animals but is broken down into glucose when consumed.

Cellulose:

Cellulose is a polysaccharide consisting of glucose units linked by β(1→4) glycosidic bonds, forming linear chains. Cellulose is a structural component of plant cell walls and provides rigidity and strength to plants. It is not digestible by humans and cannot be used for energy. However, it acts as dietary fiber, aiding in digestion.

Process of Glycogen Storage and Mobilization

Glycogenesis: The process of converting excess glucose into glycogen for storage is called glycogenesis. During this process, glucose is phosphorylated and then added to a growing glycogen chain.

Glycogenolysis: When glucose is needed, glycogen is broken down through a process called glycogenolysis. This involves the cleavage of glycogen into glucose-1-phosphate, which is then converted to glucose-6-phosphate and released into the bloodstream (in the liver) or used for energy (in the muscles).

Summary

Glycogen is the primary form of carbohydrate storage in animals, serving as a readily available reserve of glucose that can be mobilized when needed. It is stored in the liver and muscles and is crucial for maintaining blood glucose levels and providing energy during physical activity. Other forms of carbohydrates, such as glucose, starch, and cellulose, have different roles and are not used for the same purpose as glycogen.