Biomolecules and Chemistry in Everyday Life - Result Question 48
####9. The correct structure of histidine in a strongly acidic solution $(pH=2)$ is
(2019 Main, 12 Jan II)
(a)
(c)
(b)
(d)
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Answer:
Correct Answer: 9. (c)
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 $-C-OH$ 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) $pH$.
