34.4.3—And predict the results of electrophoresis

In an electric field, an amino acid or peptide moves toward the electrode of opposite charge. Its direction and speed depend on net charge, pH relative to its isoelectric point, and size/shape.

At pH below pI the species is net positive; above pI it is net negative; at pI it has no net migration. Compare every component at the stated pH.

At a pH below glycine’s pI, glycine moves toward the negative electrode; at a pH above its pI it moves toward the positive electrode.

“All amino acids move to the same side” ignores their different pI values and the chosen buffer pH.