Problem 148 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following $$ \begin{array}{ll} \text { Column-I } & \text { Column-II } \\ \hline \text { (a) Cellulose } & \text { (p) Anomers } \\ \text { (b) } \alpha-\text { D glucose and } & \text { (q) Epimers } \\ \beta-\text { D - glucose } & \\ \text { (c) Glucose and } & \text { (r) Polymer } \\ \text { Mannose } & \\ \text { (d) Protein } & \text { (s) Can be hydrolysed } \\ & \text { (t) Monomers } \\ \hline \end{array} $$

Step-by-Step Solution

Answer

(a) - (r), (b) - (p), (c) - (q), (d) - (s)

Step 1: Analyze Cellulose

Cellulose is a polymer composed of repeating glucose units linked together by glycosidic bonds. It is a type of carbohydrate that forms the structural component of plant cell walls.

Step 2: Analyze α-D Glucose and β-D Glucose

α-D Glucose and β-D Glucose are types of glucose that differ in the arrangement of the hydroxyl (OH) group at the anomeric carbon (the carbon derived from the carbonyl carbon, 1st carbon of glucose in this case). These are anomers.

Step 3: Analyze Glucose and Mannose

Glucose and Mannose are similar except for the different configuration around one asymmetric carbon in their structure. They are called epimers since they differ in configuration at a single stereogenic center.

Step 4: Analyze Protein

Proteins are large biomolecules that are polymers made up of monomers called amino acids. They can be hydrolyzed into these monomer units.

Step 5: Match Column-I to Column-II

Based on the analysis of the items in each list, we match them as follows: - (a) Cellulose → (r) Polymer - (b) α-D Glucose and β-D Glucose → (p) Anomers - (c) Glucose and Mannose → (q) Epimers - (d) Protein → (s) Can be hydrolysed

Key Concepts

Cellulose

Cellulose is a fascinating polymer found predominantly in the structure of plant cell walls. It is composed of linear chains of glucose molecules linked by glycosidic bonds, specifically β-1,4-glycosidic bonds. This arrangement allows cellulose to form strong, fibrous structures that provide rigidity and strength to plant tissues. Understanding cellulose is crucial because it is one of the most abundant organic molecules on Earth.

Here are some key characteristics and functions of cellulose:

• Insoluble in water and most organic solvents due to its extensive hydrogen bonding.
• Provides structural support in the cell walls of plants, giving them their shape and protection.
• Cannot be digested by humans, as they lack the enzyme cellulase required to break down the β-1,4-glycosidic bonds.

Despite these characteristics, cellulose is extremely important in industries like textile manufacturing and as a raw material for producing paper, showcasing its versatility and importance.

Anomers

Anomers are a type of stereoisomer found in carbohydrates. Specifically, they relate to the configuration of the anomeric carbon, which is the carbon derived from the carbonyl carbon (the C-1 position in glucose). This carbon is crucial in determining the identity of an anomer.

Anomeric differences occur when a sugar molecule forms a ring structure. Depending on the position of the hydroxyl (OH) group on the anomeric carbon, the anomer can be classified as b[1mα (alpha) or b[1mβ (beta):

• α-anomer: The hydroxyl group is trans to the CH₂OH side chain (below the plane in Haworth projection).
• β-anomer: The hydroxyl group is cis to the CH₂OH side chain (above the plane in Haworth projection).

The existence of anomers is important because it influences the properties of sugars and their ability to interact with other molecules. This concept is particularly significant in the field of biochemistry, where even slight changes in configuration can significantly alter the function and reactivity of biomolecules.

Epimers

Epimers are another type of stereoisomer in carbohydrates, differing at only one chiral center. Essentially, when two molecules, like glucose and mannose, have identical setups except for the arrangement at one specific stereogenic center, they are called epimers.

Key points about epimers:

• Epimers differ in configuration around just one asymmetric carbon atom.
• This slight structural variation can significantly change the properties and biological activity of the sugars.
• An example is glucose and mannose, which differ at the C-2 position.

Understanding epimers is crucial in fields like pharmaceutical chemistry, where the spatial arrangement of atoms in a molecule can determine its efficacy and safety as a drug.

It's fascinating to see how such a small difference can lead to diversity in functionality and interaction in biological systems.

Proteins

Proteins are large, complex biomolecules that play many critical roles in living organisms. They are polymers made up of smaller building blocks called amino acids, linked together by peptide bonds. Proteins are involved in virtually every cellular function, from catalyzing biochemical reactions as enzymes to providing structural support.

Here are some fundamental properties and functions of proteins:

• They are made of 20 different amino acids, which can be arranged in countless ways to form complex structures.
• Proteins can be hydrolyzed to break down into their amino acid building blocks, a process that is crucial for nutrient absorption and metabolism.
• Functionally, proteins act as enzymes, antibodies, hormonal messengers, and play roles in cellular communication, structure, and regulation.

The structure of proteins can be divided into four levels:

• Primary structure - sequence of amino acids.
• Secondary structure - the arrangement into alpha helices or beta sheets.
• Tertiary structure - the overall 3D shape of a single polypeptide.
• Quaternary structure - the assembly of multiple polypeptide units.

These hierarchical structures are important because the shape of a protein is directly linked to its function, emphasizing the intricate relationship between structure and activity in biochemistry.