For the zwitterion, of an amino acid, where there are 2 carboxylic acids, negative?

i just do textbook questions and what the teacher says

A sound philosophy ...

All of this is misleading, as the groups are all involved in equilibria.

The situation that exists when the molecule is neutral will correspond to the same amount of ionisation from the two carboxylic acid groups as from the protonated amine.

i.e. the SUM of the negative charges must equal the positive charge at the isoelectric point.

Hey can I just ask is that at the isoelectric point?

That's what it says ...

:/

How can that happen, if the isoelectric point has no charge.