Accepted
at 8:04 p.m. Jun, 26, 2026
by
Brian_BH
Author:
jasmvine
Type of change:
Updated content
Rationale for change
Also mentioned in Kaplan's MCAT Biochemistry 2026-2027 Amino Acids, Peptides & Proteins chapter.
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Text
A high pH will cause amino acids to be {{c1::fully deprotonated}}.
Extra
Since each group of amino acids has its own pKa value, the ionization state of them changes with pH.
Amino acids exist at physiological pH (pH 7.4) as dipolar ions with an unprotonated carboxyl group (-COO-) and a protonated amino group (-NH3+).
In acidic solutions (e.g. pH 1), amino groups are protonated (-NH3+) and carboxyl groups are also protonated (-COOH). As the pH increases, the carboxylic acid donates a proton. The bipolar form persists until pH approaches 9 and protonated amino groups lose protons.
Amino acids exist at physiological pH (pH 7.4) as dipolar ions with an unprotonated carboxyl group (-COO-) and a protonated amino group (-NH3+).
In acidic solutions (e.g. pH 1), amino groups are protonated (-NH3+) and carboxyl groups are also protonated (-COOH). As the pH increases, the carboxylic acid donates a proton. The bipolar form persists until pH approaches 9 and protonated amino groups lose protons.
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