1A: Amino Acids & Proteins —Foundational

All $L$-amino acids are $(S)$ by CIP notation.

Glycine is achiral because its $b1$-carbon is part of the planar carboxyl group.

$L$-cysteine is $(R)$ by CIP notation because sulfur in its side chain outranks the carboxyl group in priority.

The $D/L$ system and the $R/S$ system are interchangeable ways to name the same configuration.