The coiling in an a-helix is stabilized by

Question

hydrogen bonding of the N–H groups on one amino acid and the C=O groups on another.

the hydrophobic nature of the R chains, which causes the chain to coil with the R groups inward.

repulsion of the R chains from each other, causing the coil to form with the R groups on the outside.

disulfide bond formation between cysteines that are regularly spaced along peptide chains

.the N–C–C repeat of the peptide backbone, allowing for regularly spaced peptide bonds between chain segments.

Answer 1

The first answer is correct

In general, secondary structures like alpha helices and Beta sheets are stabilized by hydrogen bonding. For the helix this occurs between the amine and carboxyl groups of every four amino acids (n+4), while for beta sheets, hydrogen bonding is between separate amino acid chains.