Answer:.
→The α‑helix is held together by hydrogen bonds between the amide N − H N−H and C = O C=O groups
→ In a β‑pleated sheet, the side chains are located between adjacent segments.
→ In an α‑helix, the side chains are located on the outside of the helix. .
→ The secondary level of protein structure refers to the spatial arrangements of short segments of the protein
Explanation:
This is the level of protein which results from spatial arrangement produced by the formation of hydrogen bonds between the oxygen atom of one carboxyl group(c=0) group, and hydrogen of the NH group of amino acids four places ahead of it .( The resulting structure is coiled and are therefore called alpha-helices)
AND
Hydrogen bonds between adjacent amino acids that join them side by side so that the bonds appear straight rather than coil, and the chains form upwards-downwards-upward- downwards format to form flat shaped structure called beta-pleated sheet.
The hydrogen bonding is due to strong polarities of the –NH- CO- groups of amino acids.
The two structures account for the spatial arrangement of secondary protein structure. Secondary structure is stabilized by the orientation and aggregation of these hydrogen bonds. . The outwards distributions of the side chains, the non-polar nature (hydrophobic) of alpha-helix makes some secondary proteins ideal as integral membrane proteins.
Note- peptide bond stabilizes primary protein structure.
