Question

Two polypeptides connect as their alpha-helical rods wrap around each other to form a rope-like...

Answer 1

The question is about the alpha-helix, a secondary structure in proteins where the polypeptide chain forms a helix stabilized by hydrogen bonds, with 3.6 residues per turn.

Step-by-step explanation:

The student's question pertains to a structural arrangement known as an alpha-helix, which is a specific type of secondary protein structure. In an alpha-helix, the polypeptide chain acquires a coil shape, spiraling clockwise from the N-terminus to the C-terminus. This structure is stabilized by hydrogen bonds that form between the carbonyl groups and amine groups in the backbone, with the side chains, or R groups, extending outward.

Each turn of the alpha helix has 3.6 amino acid residues, and the helical structure maintains its shape due to these hydrogen bonds, which create bridges within the same strand. Cumulatively, these hydrogen bonds contribute to the stability and functionality of proteins. Additionally, this alpha-helix can intertwine with another alpha-helix to form a coiled, rope-like structure, contributing to the protein's tertiary structure.

Answer 2

The question involves the properties of alpha-helices in proteins, where a polypeptide chain forms a spiral structure stabilized by hydrogen bonds. This alpha-helix can intertwine with another, creating a stable, rope-like configuration essential for the protein's structure.

Step-by-step explanation:

The student's question pertains to the structure of proteins, specifically the nature of alpha-helical structures within polypeptides. In the alpha-helix formation, the polypeptide chain adopts a coil shape, spiraling clockwise from N-terminus to C-terminus. This structure is stabilized by hydrogen bonds between the carbonyl groups and amine groups in the backbone, with side chains protruding outwards. Alpha-helices sometimes intertwine, forming stable, rope-like structures.

These helices are characterized by having 3.6 amino acid residues per turn, and the R groups extend outward from the helical backbone. Such configurations are crucial as they play a significant role in determining the protein's functional tertiary structure. Another secondary structure is the beta-pleated sheet (ß-pleated), which involves hydrogen bonds between different regions of one or more polypeptide chains that fold back upon themselves, aligning parallel or antiparallel to each other.

Additionally, it's noted that these secondary structures, like the alpha-helices and beta-pleated sheets, are integral components of most globular and fibrous proteins, contributing greatly to their structural integrity.