Chemistry - Biomolecules Question with Solution | TestHub

Given pKₐ values (2.0, 4.0, 9.5), at pH < 2, all groups are protonated $\Rightarrow$ NH₃⁺ + COOH, so A is correct.

Isoelectric point, $pI=\frac{\left(2.0+4.0\right)}{2}=3.0$

where solubility is minimum $\Rightarrow$ B is correct.

At pH = 12, both COOH $\to$ COO⁻ and NH₃⁺ $\to$ NH₂ $\Rightarrow$ fully deprotonated form, so C is correct.

No aromatic ring is present, so no yellow precipitate with concentrated HNO₃ $\Rightarrow$ D is incorrect.