AP BIOLOGY

Detailed explanation-1: -Hence, the correct answer is ‘Secondary structure’.

Detailed explanation-2: -Secondary structure The most common types of secondary structures are the helix and the pleated sheet. Both structures are held in shape by hydrogen bonds, which form between the carbonyl O of one amino acid and the amino H of another.

Detailed explanation-3: -In the alpha helix, the bonds form between every fourth amino acid and cause a twist in the amino acid chain. In the -pleated sheet, the “pleats” are formed by hydrogen bonding between atoms on the backbone of the polypeptide chain.

Detailed explanation-4: -The secondary structure consists of local packing of polypeptide chain into -helices and -sheets due to hydrogen bonds between peptide bond – central carbon backbone.

Detailed explanation-5: -The Alpha Helix. An alpha helix is an element of secondary structure in which the amino acid chain is arranged in a spiral. The kinemage linked above shows an individual alpha helix, viewed from the N-terminal end to resemble the “helical wheel” (see figure below).