Alpha Helix

Definition

The alpha helix is a common secondary structure found in proteins, characterized by a right-handed spiral arrangement of the polypeptide backbone. This helical structure is stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the amino hydrogen of another, creating a stable, coiled conformation that is crucial for protein folding and function.

5 Must Know Facts For Your Next Test

1. The alpha helix is a right-handed spiral structure, with approximately 3.6 amino acid residues per turn of the helix.
2. The hydrogen bonds between the carbonyl oxygen and amino hydrogen atoms stabilize the alpha helix, giving it a high degree of structural stability.
3. Alpha helices are commonly found in globular proteins, where they often form the core of the protein structure.
4. The presence of proline residues can disrupt the alpha helix, as proline lacks a hydrogen atom on the nitrogen atom required for the stabilizing hydrogen bonds.
5. The alpha helix is a crucial structural element that allows proteins to fold into complex, three-dimensional shapes, enabling them to perform diverse biological functions.

Review Questions

• Explain the role of hydrogen bonding in stabilizing the alpha helix structure.
  • The alpha helix is stabilized by the formation of hydrogen bonds between the carbonyl oxygen of one amino acid and the amino hydrogen of another, creating a spiral arrangement of the polypeptide backbone. These hydrogen bonds hold the structure in place, giving the alpha helix a high degree of stability and allowing it to serve as a crucial secondary structure in protein folding and function.
• Describe how the presence of proline residues can disrupt the alpha helix structure.
  • Proline residues are unique in that they lack a hydrogen atom on the nitrogen atom, which is required for the formation of the stabilizing hydrogen bonds in the alpha helix. The introduction of proline into the polypeptide chain can cause a kink or bend in the alpha helix structure, disrupting the regular spiral arrangement and potentially altering the overall protein conformation and function.
• Analyze the importance of the alpha helix in the context of protein folding and biological function.
  • The alpha helix is a fundamental secondary structure that plays a vital role in protein folding and the overall three-dimensional structure of proteins. By providing a stable, coiled conformation, the alpha helix allows proteins to adopt complex shapes that are essential for their biological functions, such as catalyzing chemical reactions, binding to specific substrates, and participating in various cellular processes. The presence and arrangement of alpha helices within a protein's structure are critical determinants of its ability to perform its intended role in the body.

Related terms

Secondary Structure: The local three-dimensional structure of segments of a polypeptide chain, such as alpha helices and beta sheets, which are stabilized by hydrogen bonding.

Polypeptide Backbone: The continuous chain of alternating nitrogen and carbon atoms that forms the backbone of a protein, to which the amino acid side chains are attached.

Protein Folding: The process by which a protein structure assumes its functional 3D shape from a random coil state, driven by various interactions between the amino acid residues.