Problem 7 - Arihant Objective Approach to Organic Chemistry for IIT JEE and NEET all Medical Entrances Part 4

Question

Cellulose is polymer of : (a) glucose (b) fructose (c) ribose (d) sucrose

Step-by-Step Solution

Answer

Cellulose is a polymer of glucose (option a).

Step 1: Understanding the Problem

We need to determine which of the given options is the monomer unit that forms the polymer cellulose. Options include: glucose, fructose, ribose, and sucrose. A polymer is a large molecule made up of repeating subunits, known as monomers.

Step 2: Definitions and Characteristics

Cellulose is a type of carbohydrate that is a primary component of plant cell walls. It is an organic polymer that consists of hundreds to thousands of glucose units linked together through β(1→4) glycosidic bonds.

Step 3: Analyzing the Options

Evaluate the options: - **(a) Glucose:** A six-carbon sugar and a common monomer in many polysaccharides. - **(b) Fructose:** A six-carbon sugar but not used in cellulose formation. - **(c) Ribose:** A five-carbon sugar, not involved in cellulose structure. - **(d) Sucrose:** A disaccharide composed of glucose and fructose, not a direct polymer.

Step 4: Identifying the Correct Answer

From the analysis in Step 3, option (a) glucose is the monomer of cellulose. The characteristic bonds in cellulose involve linking glucose units in a linear chain.

Key Concepts

Polymer

A polymer is a large molecule composed of repeating structural units, known as monomers. Imagine a polymer as a long chain where each link in the chain is a monomer. The idea of polymers extends beyond chemistry, appearing in everyday materials like plastics, DNA, and proteins. In the realm of biology, cellulose serves as an excellent example of a natural polymer.
Polymers can be incredibly complex and vary widely in their specific properties. These differences are influenced by:

• The type of monomers involved.
• The chemical bonds between monomers.
• The arrangement of monomers within the polymer chain.

Understanding these properties helps in designing materials for various applications—be it sturdy plastics or strong plant cell walls like cellulose.

Glucose

Glucose is a simple sugar and a fundamental building block in the world of carbohydrates. It is classified as a monosaccharide, which means it is a single sugar molecule. Glucose has the chemical formula C₆H₁₂O₆ and is a central energy source for living organisms.
In the context of cellulose, individual glucose units join together to form a complex polysaccharide. This occurs through specific types of covalent bonds called glycosidic bonds. The glucose units are arrayed in a linear fashion, contributing to the rigidity and structural integrity of plant cell walls.

• Essential energy source.
• Forms polymers like cellulose.

Glucose is not just important for plant structures but also plays a crucial role in metabolic processes in animals, where it is a primary energy currency.

Glycosidic bond

A glycosidic bond is a specific type of covalent bond that connects carbohydrate molecules. These bonds form through a dehydration reaction, which involves the removal of a water molecule. Glycosidic bonds are essential in building complex carbohydrates like cellulose.
In cellulose, the glycosidic bonds are of the β(1→4) type, meaning that the bonds connect the first carbon of one glucose molecule to the fourth carbon of another. This setup results in a straight chain, rather than a helical one, which is significant for the structural role of cellulose in plant cells.

• Forms through dehydration or condensation reactions.
• Crucial for creating complex carbohydrates.

By understanding glycosidic bonds, we get insights into how diverse carbohydrate structures are formed, contributing to their varied functions from energy storage to providing structural support.