Question

Acid dissociation reaction for E-amino group (side chain of Lys): (R)E-NH3+ # (R)E-NH2 + A. For a weak acid such as the side chain &-amino group of a lysine residue in a protein, if the pKa of that specific residue's E-amino group is exactly 10.0, in an environment in which the pH = 9.0, what would be the ratio of base to acid ( [ε-NH2]/[ε-NH3+1 )?

Answer 1

Answer:

0.1

Explanation:

$According \ to \ Henderson \ Hasselbalch \ equation:$

$pH = pka + log \dfrac{[A^-]}{[HA]}$

From the given question;

$log \dfrac{[\varepsilon- NH_2]}{[\varepsilon - NH_3^+]}=pH - pKa$

$\implies log \dfrac{[\varepsilon- NH_2]}{[\varepsilon - NH_3^+]}=9 -10$

$\implies log \dfrac{[\varepsilon- NH_2]}{[\varepsilon - NH_3^+]}=-1$

$\implies \dfrac{[\varepsilon- NH_2]}{[\varepsilon - NH_3^+]}=10^{-1}$

$\implies \dfrac{[\varepsilon- NH_2]}{[\varepsilon - NH_3^+]}=0.1$