what is the structure of glutamic acid and lysine at pH 2 and pH 11?

Question

what is the structure of glutamic acid and lysine at pH 2 and pH 11?

Answer 1

At pH 2, both carboxyl groups and the amino group of glutamic acid will be protonated and it will have a net positive charge.

At pH 11, both carboxyl groups and the amino group will be de-protonated and it will have a net negative charge.

 

At pH 2, the carboxyl and alpha amino group and side chain will be protonated. It will have a net positive charge.

At pH 11, carboxyl group is de-protonated, alpha amino is de-protonated and side group is de-protonated, giving it a net negative charge. 

 

Look at the pKa values of all the functional groups, and compare to the pH of the environment. This will predict whether the group is protonated or not and hence will predict the net charge on the amino acid.