Final answer:
The spiral shape of a coiled protein is called an α-helix, characterized by a helical structure stabilized by hydrogen bonds and making one turn every 3.6 amino acids.
Step-by-step explanation:
The spiral shape of a coiled protein is referred to as an α-helix. In the α-helix structure, the polypeptide chain acquires a coiled shape that spirals clockwise from the N-terminus to the C-terminus. This helical structure is stabilized by intrachain hydrogen bonds between the carbonyl oxygen atom of one amino acid residue and the amide hydrogen atom four amino acids ahead in the chain.
These hydrogen bonds are responsible for maintaining the specific shape, resulting in the helix making one turn for every 3.6 amino acids, while the side chains of the amino acids project outward from the coiled backbone.