Question

A small generic section of the primary structure of an alpha helix is given below

-amino acid1-amino acid2-amino acid3-amino acid4-amino acid5-amino acid-6-amino acid7-
A) Which amino acid residue's backbone forms a hydrogen bond with the backbone of the seventh(7th) residue?
B) which of the following peptide segments is most likely to be part of a stable alpha helix at physiological pH?
A) -Lys-Lys-Ala-Arg-Ser-
B) -Gly-Arg-Lys-His-Gly-
C) -Pro-Leu-Thr-Pro-Trp-
D) -Gly-Gly-Gly-Ala-Gly-
E) -Glu-Glu-Glu-Glu-Glu-
F) -Glu-Leu-Ala-Lys-Phe-
G) -Tyr-Trp-Phe-Val-IIe-

Answer 1

The correct answers are "amino acid3" and option F) "-Glu-Leu-Ala-Lys-Phe-"

Step-by-step explanation:

The alpha helix is one the most common secondary structures of proteins, characterized by seven residue repeating units that alternate hydrophobic and hydrophilic residues. This sequence match with the peptide segment "-Glu-Leu-Ala-Lys-Phe-", where glutamic acid (Glu) is hydrophilic, leucine (Leu) is hydrophobic; and it does not contain amino acids that disrupt alpha helix such as proline and glycine. The alpha helix structure is stabilized by hydrogen bonds within the residue's backbone, one of them stablished between the third and the seventh amino acid residues.