Amino acids are acids because they contain which functional
     Amino acids are acids because they contain which functional group?  Select one:  a. carboxyl  b. sulfhydryl  c. carbonyl  d. methyl  e. amino 
  
  Solution
Amino acids possess acidic nature due to the presence of Carboxylic group I.e. CooH group.
The CooH group has the capability to donate H+ or proton, so it act as an acid.
According to Branstead lowry theory, compound that release H+ ion is called Acid. And due to the presence of CooH group, Amino acid act like acid

