Problem 4 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is a polysaccharide? (a) Gentiobiose (b) fructose (c) dextrin (d) all of these

Step-by-Step Solution

Answer

Option (c) dextrin is a polysaccharide.

Step 1: Understanding Polysaccharides

First, let's define what a polysaccharide is. A polysaccharide is a large molecule made of many monosaccharides linked together. They are complex carbohydrates, examples include starch, cellulose, and glycogen.

Step 2: Analyze Each Option

Now, we need to evaluate each option to determine if it is a polysaccharide. - **Gentiobiose** is a disaccharide, meaning it is made up of two linked monosaccharides. Therefore, it is not a polysaccharide. - **Fructose** is a monosaccharide, a simple sugar, so it is not a polysaccharide. - **Dextrin** is a polysaccharide, formed from the breakdown of starch, therefore, it fits the definition of a polysaccharide.

Step 3: Conclusion

Based on our analysis, dextrin is the only option among the choices that is a polysaccharide. Gentiobiose and fructose do not qualify as they are not composed of many monosaccharide units.

Key Concepts

Dextrin

Dextrin is a fascinating substance that falls under the category of polysaccharides. It's a large molecule made when starch undergoes partial hydrolysis. This process breaks down starch into smaller units, leading to the formation of dextrin.

Dextrin retains the general properties of polysaccharides, such as being water-soluble and having a rather bland taste. Here are some interesting points about dextrin:

• Dextrins can be formed through the enzymatic or acid breakdown of starch.
• They are often found in products like glues, processed foods, and pharmaceuticals due to their adhesive and thickening properties.
• The molecular structure of dextrin makes it an ideal substrate in certain biochemical assays.

Understanding dextrin's role in both biological and industrial processes highlights its importance and functions as a polysaccharide.

Monosaccharide

Monosaccharides are the simplest form of carbohydrates, often termed as simple sugars. They consist of single sugar molecules, making them the most basic unit from which more complex carbohydrates are built.

A few characteristics of monosaccharides are:

• They usually have a sweet taste, making them easily recognizable as sugars.
• They are water-soluble, making them readily absorbable in the digestive system.
• Their chemical formula typically follows \(C_nH_{2n}O_n\), where "n" is commonly 5 or 6, giving rise to sugars like glucose (C₆H₁₂O₆).

Monosaccharides are crucial for energy production in living organisms. During cellular respiration, the energy stored in monosaccharide molecules, like glucose, is released and used by cells. They are also essential building blocks for more complex carbohydrates like disaccharides and polysaccharides.

Disaccharide

Disaccharides are carbohydrates composed of two monosaccharide molecules joined together by a glycosidic bond. When you think "di," remember it stands for "two." This formation gives them unique properties different from monosaccharides.

Some examples of disaccharides are:

• Sucrose, which is table sugar, is made up of glucose and fructose.
• Lactose, found in milk, consists of glucose linked to galactose.
• Maltose, typically found in malted foods, comprises two glucose units.

The digestion of disaccharides involves breaking the glycosidic bond to release the simpler monosaccharides. This hydrolysis process is vital as only monosaccharides can be absorbed through the intestinal walls. Disaccharides serve as an immediate energy source once broken down and can also contribute to certain metabolic pathways in the body.