1 Which amino acid side chains that can act as an Hdonor and
1) Which amino acid side chains that can act as an H-donor and acceptor at all pH values (0-14)?
 2)Which amino acid is commonly found in a beta or reverse turn?
 3) Which amino acid side chain could NOT form an ionic or electrostatic interaction at any pH value (0-14)?
 Options: Cysteine, Isoleucine, Aspartate, Glutamine, Methionine
 Pls explain why, thanks.
 1) Which amino acid side chains that can act as an H-donor and acceptor at all pH values (0-14)?
 2)Which amino acid is commonly found in a beta or reverse turn?
 3) Which amino acid side chain could NOT form an ionic or electrostatic interaction at any pH value (0-14)?
 Options: Cysteine, Isoleucine, Aspartate, Glutamine, Methionine
 Pls explain why, thanks.
 Solution
ans 1 .
ans 2
Proline and Glycine are frequently found in beta turns, proline because its cyclic structure is ideally suited for the beta turn, and glycine because, with the smallest side chain of all the amino acids, it is the most sterically flexible
ans 3. cysteine, isolucene ,methionine
These 9 amino acids (alanine, cysteine, glycine, isoleucine, leucine, methionine, phenylalanine, proline, valine) have no hydrogen donor or acceptor atoms in their side chains.Therefore , they cannot form ionic or electrostatic interactions.

