Final answer:
The correct answer to the question is B) Alpha, Helix. The alpha-helix is a common secondary structure formed in polypeptides due to hydrogen bonding that stabilizes the helix shape.
Step-by-step explanation:
Once 4 of 20 hydrogen bonds form between every fourth amino acid in a polypeptide chain, the chain begins to twist into the alpha-helix structure known as a(n) helix. The correct answer is B) Alpha, Helix.
Explanation of Alpha-Helix Formation
The formation of an alpha-helix occurs due to the hydrogen bonding between the oxygen atom in a carbonyl group of one amino acid and the hydrogen atom of the amino group that is just four amino acid units farther along the chain. These bonds contribute to the stability of the helix by allowing it to maintain its shape instead of unraveling like a twisted piece of string would without support. Another secondary structure formed by polypeptide chains is the beta-pleated sheet, which involves hydrogen bonding but results in a different configuration.