What type of bond is directly involved in the formation of an α-helix?
a. Peptide bonds between amino acid residues
b. Hydrogen bonds between amino acid residues
c. Van der Waals interactions between nonpolar residues
d. Disulfide bonds between cysteine residues

Verified step by step guidance

1. Understand the structure of an α-helix: It is a common secondary structure in proteins, characterized by a coiled shape stabilized by specific interactions between amino acid residues.
2. Recall the types of bonds involved in protein structures: Peptide bonds form the primary structure, while secondary structures like α-helices are stabilized by non-covalent interactions such as hydrogen bonds.
3. Focus on hydrogen bonds: In an α-helix, hydrogen bonds occur between the backbone atoms of amino acids. Specifically, the hydrogen atom of the amide group (-NH) in one amino acid forms a bond with the oxygen atom of the carbonyl group (-C=O) in another amino acid located four residues earlier in the sequence.
4. Eliminate incorrect options: Peptide bonds are part of the primary structure, not directly involved in stabilizing the α-helix. Van der Waals interactions and disulfide bonds are not the primary stabilizing forces for α-helices.
5. Conclude that hydrogen bonds between amino acid residues are the key interactions directly involved in the formation and stabilization of an α-helix.

Key Concepts

Peptide Bonds

Peptide bonds are covalent bonds that link amino acids together in a protein. They form through a dehydration reaction between the carboxyl group of one amino acid and the amino group of another, resulting in a chain of amino acids known as a polypeptide. While essential for protein structure, peptide bonds do not directly stabilize secondary structures like the α-helix.

Hydrogen Bonds

Hydrogen bonds are weak attractions that occur between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom. In the context of an α-helix, hydrogen bonds form between the carbonyl oxygen of one amino acid and the amide hydrogen of another, stabilizing the helical structure. This interaction is crucial for maintaining the secondary structure of proteins.

Secondary Structure

Secondary structure refers to the local folded structures that form within a protein due to interactions between the backbone of the polypeptide chain. Common types include α-helices and β-pleated sheets, which are stabilized by hydrogen bonds. Understanding secondary structure is vital for grasping how proteins achieve their functional shapes and roles in biological processes.