Problem 16.24 Part A The structure of the amino acid lysine (in its uncharged fo
ID: 540601 • Letter: P
Question
Problem 16.24 Part A The structure of the amino acid lysine (in its uncharged form) is shown below Which amine groups would be able to participate in hydrogen bonding? Only left amino group can participate in hydrogen bonding. Only right amino group can participate in hydrogen bonding. O H2N, NH2 No amine groups can participate in hydrogen bonding. Both amine groups can participate in hydrogen bonding. Submit My Answers Give Up Part B Is lysine likely to be water-soluble? Explain Lysine is likely to be water-soluble because it can form hydrogen bonds with water Lysine is likely to be water-soluble because it has amino groups Lysine is likely to be water-unsoluble because it can't form hydrogen bonds with water Submit My Answers Give Up Provide Feedback ContinueExplanation / Answer
Ans. #Part A. Hydrogen bond is a weak attractive force between a highly electronegative atoms (O, N, F) and a H-atoms linked to such atoms.
The criteria for H-bonds formation is that there must be -
I. A highly electronegative atom (F, N, O-atom), and
II. A H-atoms linked to such atoms (F, N, O).
The N-atom of –NH2 group forms hydrogen bond with an O-linked H-atom (say, that of –OH group).
Similarly, the H-atom of –NH2 group forms hydrogen bond with an O- or N-atom.
Therefore, both the –NH2 groups form hydrogen bond irrespective of its location.
So, correct option is- D. Both the amine groups can participate in hydrogen bonding.
#Part B. Correct option A.
Lysine is a polar amino acid because of presence of –NH2 in the side chain. Additionally, when in molecular form (but not in peptide chain), the terminal amino and carboxyl groups are also available to form H-bond with water.
Thus, formation of H-bonds between water and lysine makes is soluble in water.
Option B. Incorrect. Presence of –NH2 group does not always specifies the solubility of a compound. If the compound has bulkier hydrophobic side chain, it can mask hydrogen bonding of the amine group. Thus, the compound may not be soluble in water even through it has amine group. To be soluble in water, the compound must form H-bonds with water molecules.