Question

Select the true statements about protein secondary structure. a. The α‑helix is held together by hydrogen bonds between the amide N − H N−H and C = O C=O groups. b. In a β‑pleated sheet, the side chains are located between adjacent segments. c. In an α‑helix, the side chains are located on the outside of the helix. d. The secondary level of protein structure refers to the spatial arrangements of short segments of the protein. e. Peptide bonds stabilize secondary structure.

Answer 1

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.