I need help with zwitterion form.

Question

example would be Lysine.

 

I know the standard form just having trouble grasping the concept.

 

Thank you!

Answer 1

The zwitter ion is the neutral form, i.e. NO NET CHARGE. It will be where the COOH of the amino acid is COO- and the alpha amino group will be NH3+.  In lysine, the side chain amino will be NH2.  The best I can draw it here is 

H3N⁺-CH-COO-

.........|

........CH2CH2CH2CH2NH2

 

So, the concept is that as the pH changes, so do the charges on the carboxyl and amino group. This will depend on the different Ka values.  When in very acidic media, all are protonated (COOH, NH3+). As pH increases, COOH loses the H to become COO- but the NH3 stays that way, and this is the zwitterion.  Further increase in pH results in the NH3+ losing it's H to become NH2 and so on.