Question

Identify the polysaccharide among the following :

• A. Fructose
• B. Maltose
• C. Glucose
• D. Cellulose

Hint:

Remember the classification of common carbohydrates: Monosaccharides : Glucose, Fructose Disaccharides : Maltose, Sucrose, Lactose Polysaccharides : Starch, Cellulose, Glycogen

Answer 1

The Correct Option is D

Concept: Carbohydrates are broadly classified into monosaccharides, disaccharides and polysaccharides based on the number of sugar units present in their molecules.

• Monosaccharides are the simplest carbohydrates and cannot be hydrolysed into smaller carbohydrate units.

• Disaccharides contain two monosaccharide units joined through a glycosidic linkage.

• Polysaccharides contain a large number of monosaccharide units linked together and form high molecular mass polymers.
Therefore, to identify a polysaccharide, we need to determine which compound is made up of a very large number of sugar units.

Step 1: Examining fructose. Fructose is a simple sugar having the molecular formula \[ C_6H_{12}O_6 \] It consists of only one sugar unit and cannot be hydrolysed into simpler carbohydrates. Therefore, fructose is a monosaccharide. Hence, Option (A) is incorrect.

Step 2: Examining maltose. Maltose is composed of two glucose molecules joined through a glycosidic bond. It is represented as \[ \text{Glucose} + \text{Glucose} \] Since it contains two monosaccharide units, maltose is a disaccharide. Therefore, Option (B) is incorrect.

Step 3: Examining glucose. Glucose is one of the most important naturally occurring carbohydrates. Its molecular formula is \[ C_6H_{12}O_6 \] Like fructose, glucose consists of only a single sugar unit. Hence, glucose is a monosaccharide. Therefore, Option (C) is incorrect.

Step 4: Examining cellulose. Cellulose is a naturally occurring carbohydrate found in plant cell walls. It is made up of a very large number of \(\beta\)-D-glucose units linked together through \(\beta(1 \rightarrow 4)\) glycosidic bonds. Its general representation is \[ (C_6H_{10}O_5)_n \] where \(n\) is a very large number. Since cellulose consists of hundreds to thousands of glucose units joined together, it is classified as a polysaccharide. Therefore, Option (D) is correct.

Step 5: Selecting the correct answer. Among the given compounds: \[ \text{Fructose} \rightarrow \text{Monosaccharide} \] \[ \text{Glucose} \rightarrow \text{Monosaccharide} \] \[ \text{Maltose} \rightarrow \text{Disaccharide} \] \[ \text{Cellulose} \rightarrow \text{Polysaccharide} \] Hence, the polysaccharide is cellulose. \[ \boxed{\text{Cellulose}} \] Therefore, \[ \boxed{\text{Option (D)}} \]