Problem 132 - A Complete Resource Book in Chemistry for JEE Main

Question

The characteristics of glycosidic linkage is/ are (a) ether linkage of sugar (b) it is hydrolysed by acid (c) it is hydrolysed by alkali (d) it is also hydrolysed by specific enzyme

Step-by-Step Solution

Answer

Characteristics are (a), (b), and (d): ether linkage of sugar, hydrolyzed by acid, and hydrolyzed by specific enzyme.

Step 1: Understanding Glycosidic Linkage

A glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which can also be another carbohydrate. In its basic form, it is an ether linkage between the anomeric carbon of one sugar and the hydroxyl group of another sugar or alcohol.

Step 2: Hydrolysis by Acid

A glycosidic bond can be hydrolyzed by acid. This means that in the presence of an acidic solution, the bond can be broken down into its individual components. This process involves the addition of a water molecule, facilitated by the acidic environment.

Step 3: Reaction with Alkali

Typically, glycosidic linkages are not easily hydrolyzed by alkali. The alkaline conditions do not favor the breaking of a glycosidic bond as effectively as acidic conditions do. Therefore, hydrolysis of glycosidic bonds by alkali is not a primary characteristic of these linkages.

Step 4: Enzymatic Hydrolysis

Glycosidic linkages can also be hydrolyzed by specific enzymes. For instance, enzymes like amylase, lactase, and sucrase catalyze the hydrolysis of particular glycosidic bonds in carbohydrates like starch, lactose, and sucrose, respectively.

Key Concepts

Covalent Bond

Covalent bonds are fundamental connections formed between atoms through the sharing of valence electrons. These bonds are vital for constructing molecules and determining their properties. A glycosidic linkage, specific to carbohydrates, is a particular type of covalent bond that connects two sugar molecules. It functions like a bridge between the sugars, allowing them to link and form more complex structures. This ether linkage is formed between the anomeric carbon of one sugar and the hydroxyl group of another sugar or an alcohol. Additionally, these bonds are significant not just in structural terms, but because they play a role in how sugars interact and react within biological systems.

Hydrolysis by Acid

Hydrolysis by acid involves breaking a chemical bond using water, facilitated by an acidic environment. With glycosidic linkages, acid-catalyzed hydrolysis is a process where the bond between two sugar units is severed. This happens when an acid molecule provides protons (H⁺), which help in adding a water molecule to the linkage, leading to its cleavage.
Acid hydrolysis is quite effective because acids help stabilize the intermediate states in the hydrolysis reaction, making it easier for the bond to break. This concept is key to understanding how carbohydrates can be broken down into simpler sugars under acidic conditions, such as those found in the human stomach.

Enzymatic Hydrolysis

Enzymatic hydrolysis is a highly specific process where enzymes facilitate the breakdown of chemical bonds. Unlike acid hydrolysis, which can act non-specifically, enzymes are tailored to act on certain types of glycosidic linkages.
These biological catalysts, such as amylase, lactase, and sucrase, specifically recognize the bonds they act upon, ensuring the correct molecules are broken down.

• **Amylase:** Works on starch, breaking it down into simpler sugars.
• **Lactase:** Facilitates the hydrolysis of lactose into glucose and galactose.
• **Sucrase:** Catalyzes the breakdown of sucrose into glucose and fructose.

Enzymatic hydrolysis is not only efficient but necessary for the digestion and utilization of carbohydrates in organisms. This process demonstrates the precision and efficiency of biological mechanisms in managing complex biochemical reactions.