CAIE A-Level Chemistry Optical-Isomer Drawing Convention

Alanine, $\mathrm{H}_{2} \mathrm{NCH}\left(\mathrm{CH}_{3}\right) \mathrm{CO}_{2} \mathrm{H}$, and glutamic acid, $\mathrm{H}_{2} \mathrm{NCH}\left(\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{H}\right) \mathrm{CO}_{2} \mathrm{H}$, are two naturally occurring amino acids.

$\mathrm{H}_{2} \mathrm{NCH}\left(\mathrm{CH}_{3}\right) \mathrm{CO}_{2} \mathrm{H}$ exists as two optical isomers.

Draw three-dimensional structures of these two optical isomers.