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.

 

[DeeNos]

Hello! The reason for this is because the -COOH group in an amino acid is actually a carboxylic acid, which can donate a proton (H+) and act as an acid. On the other hand, the NH3+ group is an amine group, which can accept a proton (H+) and act as a base. This is why the NH3+ group is considered the acidic group in an amino acid and the COO- group is considered the basic group. This is important because the presence of both acidic and basic groups in an amino acid allows it to act as a buffer, helping to maintain a stable pH in biological systems. I hope this helps clarify the concept for you. Let me know if you have any further questions!