BIOMOLECULES AND ENZYMES

Detailed explanation-1: -Peptide bonds contain partial double bond character, preventing free bond rotation.

Detailed explanation-2: -Interestingly, peptide bonds have a second resonance form, as demonstrated below. This means that the peptide bond (the C=O. and N-H) all reside in a single plane. Thus, there is no rotation around the bond.

Detailed explanation-3: -d) They contain an unusually long carbon-carbon bond.-This statement is NOT true. Peptide bonds are amide linkages in which the nitrogen bears no charge.

Detailed explanation-4: -Rotation around the C-N bond in the peptide bond is restricted due to resonance delocalization as seen in the diagram below. The lone pairs on nitrogen can be delocalized in the carbonyl group giving the C-N bond a partial double bond character. This double bond character restricts rotation.

Detailed explanation-5: -Carbon atoms in single bonds rotate freely. Rotation can occur because the heaviest electron density in the bond exists along an imaginary line between two carbon nuclei.