Question

Which statements are TRUE of both α helices and β sheets? Multiple answers: You can select more than one option

A Found in the same percentage in all proteins

B Stabilized by H bonds between –NH and –CO groups

C Found in globular proteins

D Affected by amino acid sequence

E An extended conformation of the polypeptide chain

F Includes all 20 standard amino acids in equal frequencies

G Hydrophobic interactions are responsible for the primary structure

Answer 1

A. False. Because it can be found in either alpha helix or beta pleated sheets or in both and it depends on the amino acid residue.

B. True. They are stabilised by hydrogen bonds between -NH and -CO ..e.g. in alpha helix -NH of first amino acid forms hydrogen bond with -CO of 5th amino acid

In beta pleated sheets two or more segments of a polypeptide chains line up next to each other forming a sheet like structure stabilised by hydrogen bonds.

C. Ture . They are found predominantly kn globular proteins.

D. True . They are affected by amino acid sequence. For example proline cannot form alpha helix due to unusual residue group. Tryptophan tyrosine phenylalanine forms mainly beta sheets.

E. True

F. Not necessary. False

G. False . Hydrophobic are responsible for tertiary structures.