Problem 37 - A Complete Resource Book in Chemistry for JEE Main

Question

The helical structure of protein is stabilized by (a) ether bonds (b) peptide bonds (c) dipeptide bonds (d) hydrogen bonds

Step-by-Step Solution

Answer

The helical structure of proteins is stabilized by hydrogen bonds.

Step 1: Understanding the Question

The problem asks us to identify which type of bond stabilizes the helical structure of proteins, commonly known as an alpha helix.

Step 2: Analyzing Bond Types

Review the given options: ether bonds, peptide bonds, dipeptide bonds, and hydrogen bonds. Consider what each bond type typically affects or stabilizes in proteins.

Step 3: Recognizing the Role in Protein Structure

Given that ether bonds are typically not involved in protein structures, and peptide bonds primarily link amino acids in a chain, they do not necessarily stabilize the helical structure. Dipeptide bonds are similar to peptide bonds but restricted to two amino acids. Hydrogen bonds are commonly known to stabilize secondary structures like the alpha helix.

Step 4: Concluding the Right Type of Bond

The helical structure of proteins is specifically stabilized by hydrogen bonds, which form between the backbone atoms of the amino acids in the chain, giving the alpha helix its structure.

Key Concepts

Alpha Helix

The alpha helix is a fundamental component of a protein's secondary structure. It resembles a coiled spring or a spiral staircase. This shape allows proteins to adopt a compact and durable form.

In its helical shape, each amino acid in the alpha helix is spaced out at roughly 100 degrees compared to the one before it. This specific angle results in around 3.6 amino acids completing a full turn of the helix.

This structure is maintained through interactions between amino acids, but one of the most crucial for the alpha helix are hydrogen bonds. They help the helix maintain its shape despite external forces or changes. Due to the highly organized structure of the alpha helix, it often appears in various types of proteins across different organisms.

Hydrogen Bonds

Hydrogen bonds are a type of weak bond essential for many biological structures, including the alpha helix. Despite being weak individually, collectively, they provide significant stability to the protein's structure.

Within an alpha helix, hydrogen bonds form between the oxygen atom in the carbonyl group of one amino acid with the hydrogen atom of an amide group four residues away. This specific pattern is called the i, i+4 arrangement and is fundamental to maintaining the helical shape.

These bonds occur regularly along the helix and are responsible for the stability and elasticity of the alpha helix. Though many think of hydrogen bonds as purely scientific phenomena, they are a magnificent example of how nature exploits these weak interactions for significant structural roles. Their forces bound the units of the helix together, providing enough flexibility to allow proteins to function correctly.

Secondary Structure Stabilization

Secondary structure stabilization in proteins is crucial as it provides a protein with its initial shape, affecting its functionality. The secondary structure includes alpha helices and beta sheets, both maintained by similar types of bonds.

In the case of the alpha helix, hydrogen bonds play a pivotal role. The consistent pattern in which these bonds form adds remarkable strength to the overall structure. It allows the alpha helix to resist unfolding or breaking under physiological conditions.

Stabilization in secondary structures ensures that proteins can engage in their myriad roles. These roles range from responding to environmental changes to participating in complex cellular processes.

Understanding how secondary structures like alpha helices are stabilized helps us appreciate not just protein architecture, but also the immense complexity of biological organisms. These intricate details underpin many advances in biotechnology, medicine, and our broader understanding of life processes.