If gly has a positive charge in a buffer at pH 1, then gly-gly-gly in the same buffer should have which of the following charges?
A)+3
B)+2
C)+1
D)-1
E)-2

Question

Quizplus · Accepted Answer

The pH of 1 is acidic, meaning there are many hydrogen ions (H+) present. The positive charge on glycine (gly) suggests that it has lost an electron and gained a proton (H+) at this low pH. Glycine has two ionizable groups, its carboxylic acid (-COOH) and its amino group (-NH3+). At pH 1, both groups are in their protonated form, with the carboxylic acid group having a net charge of 0 and the amino group having a net charge of +1. Therefore, in the tripeptide gly-gly-gly, the three glycines will each have a net charge of +1 due to their protonated amino groups. Adding these up, we get a total charge of +3. Thus, the correct answer is C.

If Gly Has a Positive Charge in a Buffer at PH