How do acids and basses differ in a water solution?
Acids form salts, bust bases do not
Negatively charged amino acids are acidic bacause they gave a proton (H+) to the solution. The amino acid was not charged before it went into the solution, but lost a hydrogen when placed in water and became negativley charged. It also donated a proton to the solution so it is considered acidic. Similar logic applies with the basic amino acids.