Explanation:
When a substance or chemical specie accepts a proton then an acid is formed. Whereas is a substance or chemical specie tends to lose a proton then a base is formed.
Chemical formula of amino group is [tex]-NH_{2}[/tex] and it is able to lose a proton to form R-NH-R'. When it tends to gain a proton the it form R-NH_{3} compound.
Chemical formula of carboxylic group is -COOH. When it loses a proton it forms [tex]-COO^{-}[/tex] ion and whenit gains an electron then it forms [tex]-O-C-OH_{2}[/tex].
Therefore, we can conclude that the amino and carboxyl functional groups tend to form bases and acids by attracting or dropping a proton.