Secondary structure

Definition

Secondary structure refers to the local folded structures that form within a polypeptide chain due to hydrogen bonding between the backbone atoms. This level of protein structure includes common motifs such as alpha helices and beta sheets, which play crucial roles in stabilizing the overall shape and functionality of proteins.

5 Must Know Facts For Your Next Test

1. Secondary structure is primarily stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen of another.
2. The arrangement of secondary structures contributes significantly to the protein's overall three-dimensional shape, influencing its function.
3. Different types of secondary structures can coexist within the same protein, creating a complex and functional architecture.
4. The formation of secondary structures is largely determined by the sequence and properties of the amino acids in the polypeptide chain.
5. Disruptions in secondary structure can lead to misfolding of proteins, which is associated with various diseases, including Alzheimer's and Parkinson's.

Review Questions

• How do hydrogen bonds contribute to the formation and stability of secondary structures in proteins?
  • Hydrogen bonds are crucial for the formation and stability of secondary structures like alpha helices and beta sheets. They occur between the carbonyl oxygen and amide hydrogen atoms in the protein backbone, causing the polypeptide chain to fold into these specific shapes. This bonding creates a stable framework that supports the overall structure and function of the protein.
• Compare and contrast alpha helices and beta sheets as types of secondary structure in proteins.
  • Alpha helices are characterized by their right-handed spiral shape formed by hydrogen bonds between every fourth amino acid, resulting in a coiled structure. In contrast, beta sheets consist of parallel or antiparallel strands held together by hydrogen bonds between adjacent chains, leading to a flat, pleated appearance. Both structures are essential for maintaining protein stability but differ in their spatial arrangements and implications for protein function.
• Evaluate the impact of mutations on the secondary structure of proteins and how this relates to protein function.
  • Mutations can significantly alter the amino acid sequence of a protein, potentially disrupting its secondary structure. Changes in key residues may weaken or abolish critical hydrogen bonds that stabilize alpha helices or beta sheets. Such disruptions can lead to improper folding and loss of function, which is linked to various diseases. Understanding these effects emphasizes the importance of secondary structure in maintaining protein integrity and functionality.

Related terms

alpha helix: A common type of secondary structure in proteins where the polypeptide chain coils into a right-handed spiral, stabilized by hydrogen bonds between every fourth amino acid.

beta sheet: Another form of secondary structure where segments of the polypeptide chain are aligned alongside each other, stabilized by hydrogen bonds, forming pleated sheets.

hydrogen bond: A weak bond that occurs when a hydrogen atom covalently bonded to an electronegative atom is attracted to another electronegative atom, playing a key role in stabilizing secondary structures.