Which of the following statements are correct?
$\left(1\right)$ $\mathrm{\alpha }$ -amino acids present in protein are $\mathrm{\alpha }$ -L-amino acids
$\left(2\right)$ Amino acids contain $-\mathrm{N}{\mathrm{H}}_2$ as well as $-\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ group
$\left(3\right)$ Number of amino groups and carboxylic groups are always same in all $\mathrm{\alpha }$ -amino acids
$\left(4\right)$ Concentration of dipolar ion is maximum at isoelectric point
Select the correct answer from the codes given below