Do zwitterions have to be neutral?

[FROGGBUSTER]

Or would an amino acid with +, -, & + = +1 overall be considered a zwitterion as well?

---

Members don't see this ad.

 

[toothhornet88]

Or would an amino acid with +, -, & + = +1 overall be considered a zwitterion as well?

No they're always neutral. It can ONLY have 1 + and 1 - charge and in amino acids you do not take R groups into consideration

 

[Cofo]

I always thought it had to be neutral...but it must have a positive and negative charge. Zwitter in German means hermaphrodite, so think "it has both types of charges". Don't ask why I know this.

 

[FROGGBUSTER]

No they're neutral molecules. It can ONLY have 1 + and 1 - charge and in amino acids you do not take R groups into consideration

So you just ignore the R group then completely? So a zwitterion will have to have the amino side protonated and the carboxylic acid side de-protonated, and then it doesn't matter at all what charge the side chain is at?

 

[toothhornet88]

So you just ignore the R group then completely? So a zwitterion will have to have the amino side protonated and the carboxylic acid side de-protonated, and then it doesn't matter at all what charge the side chain is at?

correct!

"There are four amino acids with charged side chains. Aspartic acid and glutamic acid have carboxyl groups on their side chains. Each acid is fully ionized at pH 7.4. Arginine and lysine have side chains with amino groups. Their side chains are fully protonated at pH 7.4"


THEREFORE, since the zwiterion only occurs at neutral pH the side chains at this pH are not charged