posted by lila .
Serine exists in its zwitterion form at a pH of 5.7. Draw the structural formula for the same. Explain the manner in which the structural formula of polar and non-polar amino acids would vary
You have to look at the Pka's of the carboxylic acid and the amine to know if they will be charged at a pH of 5.7; the amine will be positively charged and the carboxylic acid will be negatively charged at a pH of 5.7.
I can not draw structures on this forum, but I am pretty sure that you can google an image of the structure with the indicated charges.