Biomolecules and Chemistry in Everyday Life - Result Question 9
9. The correct structure of histidine in a strongly acidic solution $(pH=2)$ is
(2019 Main, 12 Jan II)
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Answer:
Correct Answer: 9. (a)
Solution:
- Histidine has following structure in
At highly acidic $pH$, i.e. $2$ both the nitrogens with lone pairs will accept one $H^{+}$each and will not loose its $H^{+}$. Thus, the final structure of histidine at $pH=2$ will be
Thus, option (d) is the correct answer.
Note: Amino acids have following generalise structure:
They have the tendency to loose $H^{+}$ of their $-COOH$ group at alkaline (higher) $pH$ while the $-NH _2$ group present in them have the tendency to gain $H^{+}$at acidic (lower) $pH$.
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