Final answer:
A polypeptide or protein is the most likely compound to form a stable alpha helix structure, which is a spiral shape stabilized by hydrogen bonds. The R groups of the amino acids protrude from the helix chain. This structure is found in most globular and fibrous proteins and has a significant structural role.
Step-by-step explanation:
The most likely compound to form a stable alpha helix is a polypeptide or protein. The alpha helix structure is formed by folding the polypeptide chain into a spiral shape, with hydrogen bonds stabilizing the structure. The R groups of the amino acids protrude out from the helix chain. This secondary structure is found in most globular and fibrous proteins and plays an important structural role.