What Groups Makes Amino Acids and Fatty Acids Acidic

Question

What groups makes amino acids and fatty acids acidic?  
A) Carbonyl
B) Hydroxyl
C) Ketone
D) Carboxyl
E) Acetyl

Accepted Answer

Carboxyl groups, which are present in both amino acids and fatty acids, are acidic. When they dissociate, they release hydrogen ions into solution, making them acidic.