Problem 161 - A Complete Resource Book in Chemistry for JEE Main

Question

Complete hydrolysis of cellulose gives (a) D-fructose (b) D-glucose (c) D-ribose (d) L-glucose

Step-by-Step Solution

Answer

(b) D-glucose

Step 1: Understand Cellulose Composition

Cellulose is a polysaccharide made up of repeating glucose units linked by β-1,4-glycosidic bonds.

Step 2: Define Hydrolysis

Hydrolysis is the chemical process that breaks down polysaccharides into their monosaccharide components using water and often an acid or enzyme as a catalyst.

Step 3: Apply Hydrolysis to Cellulose

When cellulose undergoes complete hydrolysis, the β-1,4-glycosidic bonds between the glucose units in cellulose are broken, resulting in the production of D-glucose molecules.

Step 4: Evaluate Given Options

Look at the options provided: (a) D-fructose, (b) D-glucose, (c) D-ribose, and (d) L-glucose. Based on the chemical process of cellulose hydrolysis, the correct answer corresponds to the production of D-glucose.

Key Concepts

Polysaccharide

Polysaccharides are complex carbohydrates that consist of long chains of monosaccharide units. These units are bonded together by glycosidic bonds, creating elaborate structures. Polysaccharides serve various roles in living organisms, fulfilling both structural and storage purposes.
In plants, cellulose serves as a prime example of a structural polysaccharide. Cellulose is composed of repeating glucose units linked together, forming a sturdy natural fiber that gives plants their rigidity and strength. These repeated glucose units are bonded by a specific type of glycosidic linkage, making cellulose particularly robust.

• Cellulose: A natural, tough, fibrous polysaccharide.
• Stores glucose units, specifically bonded for structural integrity.
• Prevalent in plant cell walls.

Understanding the structure and function of polysaccharides is essential in biology and biochemistry as they play crucial roles in various biological processes.

Glucose

Glucose is a simple sugar, also known as a monosaccharide, and is an essential energy source for organisms. It is ubiquitous in life processes and serves as a building block for complex carbohydrates like polysaccharides.
In the context of cellulose, glucose makes up the repeating units that form this polysaccharide. During cellulose hydrolysis, these glucose units are released as individual molecules.

• Basic monosaccharide, necessary for energy.
• Converted from starch and cellulose through enzymatic reactions.
• Exists in several structural forms, with D-glucose being the most common in nature.

The chemical structure of glucose allows it to participate in various metabolic pathways, highlighting its pivotal role in both energy metabolism and the formation of critical biological compounds.

Glycosidic Bonds

Glycosidic bonds are a type of covalent bond that connects carbohydrate molecules. They play a pivotal role in forming polysaccharides, linking monosaccharide units into longer chains. These bonds are formed via a dehydration reaction, where a molecule of water is removed.
For cellulose, these bonds take the form of β-1,4-glycosidic linkages. This specific arrangement gives cellulose its strength and makes it resistant to digestion in most animals. However, through the process of hydrolysis, cellulose can be broken down by enzymes that specifically target these bonds.

• Link monosaccharides to form complex carbohydrates.
• Crucial for the structure and integrity of polysaccharides like cellulose.
• Can be broken down via hydrolysis, reversing the dehydration synthesis.

The breakdown of these bonds is a critical step in converting cellulose into glucose, which is then utilized by organisms for various biological functions.