Problem 38 - A Complete Resource Book in Chemistry for JEE Main

Question

Fibrous protein are insoluble in (a) water (b) strong base (c) strong acid (d) both (b) and (c)

Step-by-Step Solution

Answer

Fibrous proteins are insoluble in both strong base and strong acid (d) both (b) and (c).

Step 1: Understanding Fibrous Proteins

Fibrous proteins are a type of protein that are usually composed of elongated and insoluble sheets or strands. These proteins include collagen, keratin, and elastin, which are known for being insoluble and play structural roles in cells and tissues.

Step 2: Solubility in Water

Fibrous proteins tend to be insoluble in water due to their structural nature. Their elongated, filamentous form does not easily interact or dissolve in water, especially compared to globular proteins.

Step 3: Reactivity with Strong Base and Acid

Fibrous proteins are generally stable and resistant to denaturation by both strong bases and strong acids. This stability is due to their primary function of providing structure, requiring a strong and stable structure that is not easily altered by pH changes.

Step 4: Drawing the Conclusion

Given the insoluble nature of fibrous proteins in water and their stability against strong acids and bases, fibrous proteins are understood to be insoluble or resistant to strong acidic and basic environments.

Key Concepts

Protein Solubility

Protein solubility refers to the ability of a protein to dissolve in a solvent, typically water. Solubility can depend on various factors, such as the protein's structure, the solvent's properties, and environmental conditions like temperature and pH. In the case of fibrous proteins, their long, thread-like structures make them insoluble in water. Unlike globular proteins, which have compact and generally hydrophilic surfaces, fibrous proteins have extensive hydrophobic regions that repel water. This characteristic keeps these proteins intact and insoluble even in aquatic environments.

Factors affecting protein solubility:

• Polarity: Hydrophobic regions decrease solubility, while hydrophilic regions increase it.
• pH Levels: Extreme pH levels can alter solubility by changing protein charge.
• Temperature: Increased temperatures can lead to denaturation, affecting solubility.

Understanding these variables helps in applications where protein solubility is a vital factor, such as drug delivery and food industry processes.

Structural Proteins

Structural proteins are crucial components that provide support and shape to cells and tissues. The common characteristic of these proteins is their fiber-like structure, contributing to their strength and rigidity. Examples include collagen, keratin, and elastin. These proteins are specifically designed to bear tension and contribute to the physical properties of tissues, like elasticity in skin or tensile strength in connective tissues.

Key roles of structural proteins include:

• Maintaining cell shape: They form the cytoskeleton which gives cells their shape.
• Joining cells together: Structural proteins connect cells within tissues, promoting mechanical strength.
• Protecting tissues: Their robust nature helps in withstanding physical stress.

Hence, without structural proteins, the body's architecture would be compromised, leading to weakened cellular and tissue integrity.

Protein Denaturation

Protein denaturation refers to the structural alteration of a protein, which may result from external factors such as heat, pH changes, or chemical exposure. Denatured proteins lose their functional shape and, therefore, their biological activity. In fibrous proteins, the potential for denaturation is reduced because of their stable and resilient nature, required for their structural role.

Key factors leading to denaturation:

• Heat: High temperatures can disrupt protein structures, causing them to unfold.
• pH Levels: Extreme pH can lead to ionization changes, weakening protein stability.
• Chemicals: Agents such as urea or detergents can disrupt hydrogen and disulfide bonds.

Understanding the denaturation process is important to prevent loss of protein activity in various scientific and industrial applications, emphasizing the need for stable conditions when dealing with these biomolecules.