Cho các amino acid: H2N[CH2]5COOH; (CH3)2CHCH(NH2)CH2COOH; HOOCCHCH2CHH2)

Cho các amino acid:

$\text{H}{}_2 \text{N}\left[\text{C}\text{H}{}_2\right]{}_5\text{C}\text{O}\text{O}\text{H};\left(\text{C}\text{H}{}_3\right){}_2\text{C}\text{H}\text{C}\text{H}\left(\text{N}\text{H}{}_2\right)\text{C}\text{H}{}_2\text{C}\text{O}\text{O}\text{H};\text{H}\text{O}\text{O}\text{C}\text{C}\text{H}\text{C}\text{H}{}_2\text{C}\text{H}\text{H}{}_2)\text{C}\text{O}\text{O}\text{H}$; $\text{H}{}_2\text{N}\text{C}\text{H}\left(\text{C}\text{H}{}_3\right)\text{C}\text{O}\text{O}\text{H};\text{H}{}_2\text{N}\text{C}\text{H}{}_2\text{C}\text{O}\text{O}\text{H}$. Có bao nhiêu chất thuộc loại $\alpha$-amino acid?