Kaplan MCAT question help - amino acids

[neuropanic]

I understand why the correct answer is correct, however I don't understand how another answer choice is incorrect and Kaplan's explanation is not very good..

"The five-membere iminoring of the amino acid proline prevents the alpha- amine nitrogen from participating in hydrogen bonding. Which of the following is most likely true?

Correct answer: Proline decreases the stability of beta-pleated sheets.
Wrong answer: Proline cannot act like a Bronsted-Lowry base.

Their explanation is that because it cannot participate in hydrogen bonding, it disrupts beta- sheets. However, wouldn't this also be true for Bronsted- Lowry base?? They said that the alpha-amino nitrogen can still bind a proton and become a quaternary amine. How can it not bind a hydrogen but can bind a proton?????
Am I just thinking about this wrong on the basis of inter v. intra molecular forces?

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[Tintinnabula]

Seems to me that the correct answer is correct because it addresses the question's interest: H-bonding/weak bonding forces. Forming a B-L base is not a weak bonding action. The question is testing to make sure that you understand what actually constitutes the weak intermolecular bonding forces.

 

[hoihaie]

proline by itself still has carboxylic acid group that can participate in acid-base rxn.