which one is incorrect Which one of the following 5 statemen

which one is incorrect?
Which one of the following 5 statements is incorrect?

A. In a peptide, the bonds between the amino group and the alpha carbon atom and between the alpha carbon atom and the carbonyl group are pure single bonds.

B. When a peptide bond is formed between the alpha-carboxyl group of one amino acid and the alpha-amino group of another amino acid, both the amino and carboxyl groups can still be charged.

C. Alpha helices have a tightly coiled backbone, whereas beta-strands are almost fully extended.

D. Disulfide bonds can form between cysteine residues in the same polypeptide chain or they can link to separate polypeptide chains together.

E. In a pair of peptide-bonded amino acids, six atoms (C-alpha, C, O, N, the amide-N\'s H, and C-alpha) lie in a plane

Solution

In the above statements regarding peptide bonds, the statement B is incorrect,

Because, when a peptide bond is formed between the alpha-carboxyl group of one amino acid and the alpha-amino group of another amino acid, it becomes uncharged but remains polar, i.e. peptide bond neither accept nor give off protons. So, both the amino and carboxyl groups remains neutral.