14. In the a-helical secondary structure, the amino acid side chains A. are buri
ID: 194746 • Letter: 1
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14. In the a-helical secondary structure, the amino acid side chains A. are buried in the interior of the helix 8 provide the hydrogen bonds that form the helix C. are typically pola D. extend outward from the helix spiral E. are located in an alternating arrangement between the inside and the outside of the helib 15. All of the following are considered 'weak interactions in proteins, except A) hydrogen bonds. C) ionic bonds D) peptide bonds E) van der Waals forces 16. In the diagram below, the plane drawn behind the peptide bond indicates the absence of rotation around the C-N bond because of its partial double-bond character plane of rotation around the A) C-N bond B) C) region of steric hindrance determined by the large CsO group D) region of the peptide bond that contributes to a Ramachandran plot E) None of the above 17. Which of the following pairs of bonds within a peptide backbone show free rotation around both bonds? A) Ca-C and N-C B) C-O and N-C C) CO and N-Ca N-C and Co-c N-Ca and N-C D) E) 18 Roughly how many amino acids are there in one turn of an -helix? A) 1 B) 2.8 C) 3.6 D) 6 E) 10 19 Thr and/or Leu residues tend to disrupt an helix when they occur next to each other in a protein because A) an amino acids like Thr is highly hydrophobic.Explanation / Answer
14. Option D is the correct answer. The R side chain residues are present outward from the alpha helix spiral, this allows it to maintain its shape.
15. Option D is the correct answer. Peptide bonds consist of covalent interaction which is stronger bonds than all of the interaction mentioned here.
16. Option A is the correct answer. Here in the diagram, the arrow between C and N bond shows absence of rotation around the C-N bond. Here C-N bond of peptide shows partial double bond character due to the presence of lone pair of electron on nitrogen atom which take parts in resonance. Due to this partial double bond character the bond length between C and N of peptide bond is decreases. This decrease in peptide bond length restrict the rotation of bonds around it.
17. Option D is the correct answer. Here all pairs except D have the effect of partial double bond character of peptide bond because these pairs contain bonds directlly attached with either C or N of peptide bond.
18. The correct answer is option C that is 3.6
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