At its isoelectic point, which is to say it the amino acids are neutrally charged (ie. greatest % of the amino acids in any given sample are in this state), it must exist in dipolar aka zwitterion form. If the greatest percentage of any given sample of an amino acid was in either its anionic, dianionic (for amino acids with acidic R groups), cationic, or dicationic (for amino acids with basic R groups) forms, we cannot say such a pH is its isolectric point.
Regardless, the statement "But not all molecules of aminoacids exist in dipolar form at this point" still does not justify the sweeping statement (found in a Chemistry book, which is the point of this thread), "An amino acid is LEAST soluble in water at it's isoelectric point.", now does it?
Thanks for any further replies.