Question

Multiple Choice Question, Please Pick the Correct Option for Each Question (Only one option is correct per question)

Part A The amino acid that destabilizes alpha-helical structures and is usually found at the ends of alpha helices is O Alanine Glycine Asparagine O Glutamate PART B Proline is NOT often found in a-helices of proteins because it O Lacks a hydrogen atom on its amide nitrogen O Interacts with adjacent amino acids Has a very bulky side chain O Has a small, uncharged side chain

Answer 1

Answer-

A) The amino acid that destabilizes alpha helical structures and is found at the end of alpha helical structures is Glycine.

  Glycine is found rarely in alpha helix because it has more conformational flexibility than other amino acids (the side chain of Glycine is -H). This makes it entropically expensive to form alpha helical conformation. Difference in free energy change, relative to that for alanine (alanine has the greatest tendency to form alpha helix), required for glycine is 4.6 kJ/mol (very higher) to make alpha helix.

B) Proline is not often found in alpha helices of proteins because it lacks a hydrogen atom on its amide nitrogen.

Proline is a nonpolar amino acid which has an aliphatic side chain with cyclic structure. The amide nitrogen is bonded to carbon of side chain to form a cyclic structure. So, amide nitrogen of proline lacks a hydrogen atom. This means nitrogen atom has no substituent hydrogen to participate in hydrogen bomds with other residues.