Question

Part 1 (1 point) See Hint Due to its partial double bond character, the peptide bond restricts rotation, constraining atoms to lie within the same peptide plane. Rotation in the peptide backbone is around the two bonds that flank adjacent Ca atoms, between which a peptide plane is formed. Part 2 (1 point) See Hint What is the molecular geometry of the constituents of the peptide plane? Choose one: A. The amide nitrogen is tetrahedral and the carbonyl carbon is trigonal planar. B. The amide nitrogen is trigonal planar and the carbonyl carbon is also trigonal planar. C. The amide nitrogen is trigonal bipyramidal and the carbonyl carbon is trigonal planar. OD. The amide nitrogen is tetrahedral and the carbonyl carbon is also tetrahedral. Part 3 (1 point) See Hint It has been observed that in a few cases, the peptide plane is actually bent 4°-5° from being a flat plane. What is the most plausible explanation? Choose one: A. The skewed peptide plane is a result of misformed disulfide bonds, causing the protein to denature. B. Some other restraint is causing the peptide plane to adopt an unfavorable state. The favorable energetics of the other restraint offset the energetic unfavorability of the skewed peptide plane. O C. This is not possible. The apparent skewing of the peptide plane must be due to error in the structural measurement. OD. The fast, dynamic motions in a protein cause the peptide plane to be non-ideal over the lifetime of the protein.

Answer 1

1. The answer

Rotation in the peptide backbone is around the two bonds that flank adjacent $\alpha$ C and Nitrogen or $\alpha$ C and carbonyl carbon atoms.