Similarities beteween crystine, glycine, and alanine?

Question

Which parts of the molecules are the same?

Answer 1

All amino acids have the same base ... their definition comes from one variable bonding point, where different elemental combinations attach to the focal Carbon of the molecule. The central Carbon molecule has one COO- group, one NH3+ group, and one Hydrogen atom. The fourth bonding point is where the variations among the 20 amino acids take place.

Alanine - fourth group is CH3
Glycine - fourth group is H
Cysteine (the closest to your crystine) - fourth group is CH2-SH

Amino acids are the lego blocks used to make proteins

Answer 2

Ice is correct-- the structure is basically the same, only the "R" group changes.