The R-group of histidine is a weak base with a pKb of 6.0. Calculate the percent ionization at pH 7.4.

What is the net charge of the following amino acids (single letter codes used) at pH7.4?

Glycine

Serine

Glutamic Acid

Lysine

Please help. I'm not sure how I'm supposed to know these problems. My professor did not go over it in class.