Acidity and basicity in amino acids

[Rujano]

Hello! I'm having a hard time understanding the acidity and basicity of amino acids.

I read this: the acidic group in an amino acid is NOT the -COOH but the NH3+ and the basic group is COO- and not the NH2... why?

Thanks in advance!

 

[epenguin]

Just revise about "conjugate acids and bases" e.g.

http://chemwiki.ucdavis.edu/Physical_Chemistry/Acids_and_Bases/Conjugate_Acids-base_Pairs#Conjugate_Acid-Base_Pairs

"The conjugate acid of a base is formed when the base gains a proton" etc.

 

[SteamKing]

The proper term for 'basicity' is 'alkalinity'.

 

[chemisttree]

Hello! I'm having a hard time understanding the acidity and basicity of amino acids.

I read this: the acidic group in an amino acid is NOT the -COOH but the NH3+ and the basic group is COO- and not the NH2... why?

Thanks in advance!

Individual amino acids exist as zwitterions in plain water. Therefore, the acid part will be the group with the protons and the base will be the group capable of accepting a proton. You haven't asked about the side groups yet. That's where it gets interesting.