Arginine Guanidinium Group pKa
Arginine is a basic amino acid characterized by its side chain, which contains a guanidinium group. This group is strongly basic due to resonance stabilization of its conjugate acid.
The pKa value quantifies the acidity of a group. For the guanidinium group of Arginine, the relevant pKa value is approximately 12.5.
This high pKa means that the guanidinium group is fully protonated (positively charged) under typical physiological conditions (pH around 7.4).
Key pKa values for Arginine:
- Alpha-carboxyl group: ~2.2
- Alpha-amino group: ~9.0
- Guanidinium group: ~12.5
Therefore, the pKa value of the guanidinium group of Arginine is 12.5.
Important Questions from Chemical Biology {p}K_a Henderson Hasselbalch
- The $pH$ of $10^{-8} \text{ M HCl (aq.)}$ is ________ (rounded off to two decimal places).
Given, $pK_w = 14$. The correct comparison of $pK_a$'s of $[Fe(H_2O)_6]^{2+}$, $[Fe(H_2O)_6]^{3+}$, $V_2O_5$ and $N_2O_5$ is
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a) Assertion: Acidulates are added in soft drinks to provide a buffering action.
r) Reason: Buffers tend to prevent changes in pH and prevent excessive tartness.
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