You definitely don't have to memorize the structures of the amino acids. The only thing I would consider reviewing is isoelectric points, etc. If they give you pKa's of certain groups on an amino acid you should be able to figure out its net charge at a particular pH, or predict a pH at which the total net charge of the molecule is zero.
I think I remember having a similar problem on my DAT. Basically as the pH crosses the pKa of a certain group, that group will become deprotonated. This is just a simple way of using a biochem structure to facilitate a general chem/o-chem principle.