Final answer:
The alpha-helix is a secondary structure of proteins where hydrogen bonds stabilize the helical shape by connecting the oxygen atom in the carbonyl group of one amino acid to the hydrogen of another amino acid four residues away.
Step-by-step explanation:
Alpha-Helix Secondary Structure
The alpha-helix (a-helix) is a type of secondary protein structure characterized by a helical shape that is stabilized by hydrogen bonds. In this structure, a hydrogen bond forms between the carbonyl oxygen atom of one amino acid residue and the hydrogen atom attached to the nitrogen atom of another amino acid, typically the one that is four residues away on the peptide chain. This pattern of bonding contributes to the helix's stability and is a common feature in the folding of proteins.
The flexibility of the polypeptide chain allows for the formation of several types of secondary structures, including the alpha-helix and the beta-pleated sheet (ß-pleated). Both structures rely on hydrogen bonding between the oxygen atoms in the peptide backbone's carbonyl groups and the hydrogen atoms on the nitrogen atoms of the amino groups. The a-helix specifically has hydrogen bonds that occur every fourth amino acid, creating a strong, coiled structure.