Explanation :
Zwitter ion : An ion or molecule having separate negatively and positively charged groups.
Methionine is an amino acid with sulfur atom in its molecule .The proton from carboxylic group with get attached to amino group present in the methionine and negative charge will be generated on oxygen atom of a carboxylic group which will get in conjugation with an another oxygen atom of the carboxylic group.
The positive charge will generated on the nitrogen atom due attachment of the proton from the carboxylic group.
As shown in the image attached.
