Proteins have a 'backbone' of repeating elements, based on the similar composition of amino acids. The repeating elements of a polypeptide backbone are:
A. S-C-C-S-C-C...
B. N-C-C-N-C-C...
C. N-C-O-N-C-O...
D. C-O-O-C-O-O...
E. C-P-C-C-P-C...
To determine the repeating elements of a polypeptide backbone, we need to understand the composition of amino acids and the bonds between them.
Amino acids consist of an amino group (NH2), a carboxyl group (COOH), and a side chain (R group), all attached to a central carbon atom (C-alpha). In a polypeptide chain, the amino group of one amino acid forms a peptide bond with the carboxyl group of another amino acid, resulting in the formation of a backbone.
The correct answer is B. N-C-C-N-C-C...
This is because the backbone of a polypeptide chain consists of a repeating sequence of amide bonds between the nitrogen (N) atom of one amino acid and the carbon (C) atom of the next amino acid in the chain. This sequence can be represented as N-C-C-N-C-C...