Why can histidine NOT act as a base in the lysosome (an organelle where the pH is close to 4.5)?
A)Histidine has a positive charge at pH 4.5.
B)Histidine has a side chain pK close to 6.
C)Histidine would be protonated at pH 4.5.
D)All of the above are correct.
E)None of the above is correct.

Question

Quizplus · Accepted Answer

Histidine acts as a base by accepting a proton, but in the acidic environment of the lysosome (pH 4.5), histidine's side chain (with a pKa close to 6) would be protonated and carry a positive charge, making it unable to accept further protons.

Why Can Histidine NOT Act as a Base in the Lysosome